Functional status measures for the COPD patient: A practical categorization

Introduction

Functional status measures (FSMs) are instruments generally used to evaluate the impact of a person’s health condition on their ability to perform activities. These measures have also been referred to as activity (or functional status) measures, questionnaires, instruments, or tools. FSMs were initially developed to describe an individual’s participation in activities of daily living; however, functional status is sometimes more broadly used as a term for the evaluation of other types of function such as social, psychological, physiologic, and emotional. This article will use the term FSM as it relates to the direct or indirect measurement of activity by patients with chronic obstructive pulmonary disease (COPD).

Why measure activities? FSMs can provide detailed information on what individuals do, providing a window into the daily life of patients. The development of FSMs in the 1950s and 1960s focused on grading disability or the degree to which patients required assistance in the long-term residential care setting. However, since this time, expansion of the application of FSMs, such as for patients with chronic disease, has allowed clinicians to use FSMs to describe progress secondary to the disease, or in response to therapy.

In the past 30 years, there has been a great deal of interest in quantifying the degree of activity limitation for patients with COPD. During this time, activity monitors were introduced to measure activity levels as purportedly, a more reliable method due to their objective nature, as opposed to the subjective nature of FSMs. However, activity monitors have limitations in measuring small changes in daily life and patterns of activities in patients. ¹ Compared to FSMs, activity monitors have the disadvantages of expense, limitation in detecting steps in those with slow walking speed, evaluation of predominantly lower extremity movement, and failure in some instances to provide information specific to what activity is being performed, ² for example, making a bed versus washing the dishes. More recently, attempts have been made to evaluate patients with both types of measures, resulting in complimentary information being gathered. ¹

Numerous FSMs exist, most developed for purposes of measuring activities in patients other than COPD. Many have the potential to be applied in the COPD population after the measure has undergone appropriate psychometric testing. For example, the Nottingham Extended Activities of Daily Living Scale ³ was developed in the 1980s for use with stroke patients, and has now been validated for use in the COPD population. ⁴ This transferability of FSMs between patient population groups has led to a vast array of measures being available to clinicians, with a potential for confusion over which measure is the most appropriate for specific scenario use. Observing patterns of uniqueness of measures led the authors of this article to consider categorizing FSMs to support clinicians in decision-making. Providing a categorical framework of FSMs for the pulmonary community would be beneficial for greater clarity in the selection and informed application of these measures.

The purpose of this article is to review available FSMs that have been validated for use in the COPD population and categorizing the measures by their commonalities. Characteristics and unique qualities of the instruments will be highlighted, and a framework for selection of a measure will be presented to support the appropriate application of the measures for both clinicians and researchers. The features presented will include ease of use (reflected in time to administer, scoring, etc.), time frame, psychometric properties (e.g. validity, reliability, responsiveness), and minimal clinically important difference (MCID).

Methods

Establishing the FSM categories was completed in three phases. First, FSMs were identified that were commonly used in COPD patients through a literature search of PubMed and Google Scholar. Three recent systematic reviews of FSMs were identified, published in 2014 and 2016 ^{5 –7} and FSMs presented in these systematic reviews obtained. A reference list check of all papers included in the review was also completed to source all FSMs for use with COPD patients. Measures that were included in the synthesis had to meet the following criteria:

Instruments were excluded if they were not found to have been used in COPD patients, were never tested or used beyond the initial development after 5 years or more, have not been used for measurement with the COPD population for a decade or more, or where the scoring system changed too frequently to reliably report the psychometric properties. Papers considered for inclusion were reviewed by the two authors, and consensus reached on inclusion by discussion.

The second phase was to complete a subsequent search of PubMed and Google Scholar to obtain copies of the measures and the literature reporting on the psychometric properties of all FSMs identified for inclusion. The psychometric properties of the FSMs were then extracted from the papers by one author. While psychometric properties often receive less attention, inadequate testing of measures may result in failure to obtain the desired information about the patient/study, or provide false or misleading conclusions. Responsiveness of the instrument measuring the activity for impact of COPD or following treatment (e.g. pulmonary rehabilitation) was also recorded. The MCID of the measure was noted; however, as this information was not always available, papers were not excluded if MCID had not been determined.

Descriptive analysis of the components of the measures was then undertaken by one of the authors, grouping papers based on the purpose of the FSM, number of activities evaluated, how the activities were evaluated, how the FSM was administered, and whether it was tested and used in COPD patients. Finally, the instruments were thematically organized according to concepts. Initially, information on the types of activities measured, the number of activities evaluated, time taken to complete the entire measure, total number of items (questions) in the measure, time frame for administering, psychometric measurement properties (as previously described), and process of completing the measure, including scoring and whether nominal, ordinal, or interval scores, were extracted from the papers. The purpose of the FSM was the primary driver in developing the themes.

Results

A total of 61 FSMs were identified, with 35 included in this review and thematic analysis. A list of all FSMs reported for use with COPD patients are provided in Table 1, noting rationale for those excluded. The main reasons for exclusion were, they had either not been tested in the COPD population or testing was limited to the initial instrument development.

OPEN IN VIEWER

Table 1.

List of FSMs considered for inclusion with reasons for exclusion.

Measure	Included/excluded	Reason for exclusion
Activities Checklist 8	Excluded	No known use in COPD patients
Activities of Daily Living Index (AKA Frenchay Activities Index) 9	Excluded	No known use in COPD patients
Activities of Daily Living Inventory (ADLI) 10	Excluded	No known in COPD use since original development, and limited testing
Activities of Daily Living Questionnaire (ADLQ) 11	Excluded	Last known use in COPD patients >10 years.
Activities of Daily Living Test 12	Excluded	No known use in COPD patients
Activities of Daily Living Simulation Test 13	Excluded	Limited psychometric testing. Performance and types of activities altered in studies of COPD patients.
Adelaide Activities Profile (AAP) 14	Excluded	No known use in COPD patients
Baecke Physical Activity Questionnaire 15	Excluded	Types of activities designed for healthy, active elderly
Barthel Index (BI) 16	Included
Barthel Index Modified (BIM) 17	Included
Baseline Dyspnea/Transitional Dyspnea Index 18	Included
Canadian Occupational Performance Measure (COPM) 19	Included
Capacity of Daily Living in the Morning (CDLM) 20	Excluded	Activities specific to morning symptoms
Chronic Respiratory Disease Questionnaire (CRQ or CRDQ) 21,22	Included
Clinical COPD Questionnaire (CCQ) 23	Included
COPD Activity Rating Scale (CARS) 24	Excluded	First and last known use in 2003 when developed.
Community Healthy Activities Model Program for Seniors (CHAMPS) 25	Included
Customary Activity Questionnaire 26	Excluded	Last known use in respiratory in 1998
Duke Activity Status Index (DASI) 27	Included
EuroQOL-ED 5D-5 L and VAS 28,29	Included
Fitness Arthritis and Seniors Trial (FAST) 30	Excluded	No known use in pulmonary patients
Frenchay Activities Index (FAI) 9	Excluded	Multiple versions of scoring and variable number of activities make the FAI difficult to evaluate reliably
Functional Activities Questionnaire 31	Excluded	No known use in COPD patients
Functional Performance Inventory (FPI) 32	Included
Functional Performance Inventory (Short Form) (FPI-SF) 33	Included
Functional Status Questionnaire 34	Excluded	No known use in COPD patients since 1980s
Glittre Test 35	Included
Groningen Activity Restriction Scale (GARS) 36	Included
Human Activity Profile (HAP) 37	Included
Index of Independent Activities of Daily Living Scale (Index of ADL) 38	Excluded	Limited testing and little use in COPD
Instrumental Activities of Daily Living 39	Excluded	Last known use in COPD patients was 1994
Karnofsky Performance Scale (KPS) 40	Excluded	Measure of functional impairment (health to death)
London Chest Activity of Daily Living Scale (LCADL) 41	Included
London Handicap Scale 42	Excluded	Measure of handicap
Londrina Activities of Daily Living Protocol 43	Included
Manchester Respiratory Activities of Daily Living Questionnaire (MRADL) 44	Included
Meaningful Activity Participation Assessment (MAPA) 45	Excluded	Developed for those with mental illness to describe the quality/meaningfulness of activities
Medical Research Council (MRC) 46,47	Included
Milliken ADL Scale (MAS) 48	Included
Minnesota Leisure Time Physical Activity Questionnaire 49	Excluded	Limited use in COPD patients
Monitored Functional Task Evaluation (MFTE) 50	Included
Motor subscale of the Functional Independence Measure (FIM) 51	Excluded	Designed for inpatient rehabilitation assessing mobility, toilet function and cognition, not specifically evaluated for COPD patients
Nagasaki University Respiratory Activity of Daily Living Questionnaire 52	Excluded	No known use or testing since original development in 2009
Nottingham Extended Activities of Daily Living Questionnaire (NEADL) 3	Included
Oxygen Cost Diagram (OCD) 53	Included
Oxford Participation and Activities Questionnaire (Ox-PAQ) 54	Excluded	No known use in COPD patients
Physical Activity Scale for the Elderly (PASE) 55	Included
ProActive 56	Included
Pulmonary Functional Status Scale (PFSS) 57	Included
Pulmonary Functional Status Scale (PFSS-11) 58	Excluded	Testing to limited to development
Pulmonary Functional Status Scale (Short Version) (PFSS-35) 57	Included
Pulmonary Functional Status and Dyspnea Questionnaire (PFSDQ) 59	Included
Pulmonary Functional Status and Dyspnea Questionnaire modified version (PFSDQ-M) 60	Included
Saint George’s Respiratory Questionnaire (SGRQ) 61	Included
Short Form 36 of Medical Outcomes Study (SF-36) 62	Included
Stanford 7-Day Physical Activity Recall (PAR) 63	Included
The Valued Life Activity Scale 64	Included
Townsends Disability Scale 65	Excluded	No known use in COPD patients since 1989
University of San Diego Shortness of Breath Questionnaire (SOBQ) 66	Included
Yale Physician Activity Survey (YPAS) 67	Included
Zutphen Physical Activity Questionnaire (ZPAQ) 68	Included

FSM: functional status measure; AKA: also known as; COPD: chronic obstructive pulmonary disease; VAS: visual analog scale.

Categories of measures

Five themes of measures were identified: daily activities, impact, surrogate, indirect performance-based, and disability-based measures. These themes formed five categories of measures.

Measures that looked at participation in a variety of activities were labeled Activity Measures. These measures evaluated the ability of the patient to engage in numerous activities often assessing domains of self-care, home management, ambulation, and participation in social and recreational activities.

Activities that were associated with symptoms were labeled Impact Measures. These measures evaluated how symptoms (primarily dyspnea and/or fatigue) affected the person’s ability to participate in activities. A measure that is classically used to measure dyspnea is the Medical Research Council (MRC) Scale ^46,47 ; however, because this scale focuses on the effect of dyspnea on walking limitations, it could also be considered an Activity Measure. Additionally, one could argue that the MRC reflects disability because like the Disability Measures, the MRC categorizes patients as ambulatory or housebound.

Where activities were subscales or domains of health status questionnaires, such as the physical function subscale of the Medical Outcomes Study/SF-36, ⁶⁹ these measures were labeled Surrogate Measures of activities. These subscales are often used as substitutes to establish concurrent validity of Activity Measures; however, the activities in these Surrogate Measures sometimes included evaluation of emotional function making them not purely FSMs. The domains of these health status measures comprise part of a total score that reflects overall health status or health-related quality of life. Where feasible, the psychometric properties of the individual domains/subscales were reported.

Indirect Performance-Based Measures as a category describes measures used to evaluate the individual’s potential to engage in activities by observation of typical body motions. There are limited numbers of these measures but their contribution to understanding patients’ limitations in activities made them candidates as FSMs.

Disability-Based Measures either observe and rate an activity or have the individual self-report their level of independence with activities. These instruments were initially designed for patients in long-term care settings such as nursing homes or those limited in activity due to stroke or orthopedic surgery.

Figure 1 provides a pictorial illustration of how these categories address functional status. For example, the Activity Category measures “do you do it (the activity listed)?” In relation to activities, the Disability Category asks, “can you do it?” and so on.

OPEN IN VIEWER

Figure 1.

An illustration of the five categories of functional status measures.

Of the measures identified, 17 instruments were deemed to fit in the category of Activity, 5 Impact, 5 Surrogate, 3 Performance-based, and 5 Disability-based measures. It was noted that some measures could be considered overlapping with other categories. For example, FSMs among the Impact Measures were a reflection of both an individual’s participation in activities (Activity Measure) and symptoms with the activity (Impact). However, because these measures ask what activities individuals have reduced or no longer perform because of dyspnea (e.g. Oxygen Cost Diagram, MRC, etc.), they were also candidates for being considered Activity Measures. Where there was overlap, these measures are noted in the comment column of each table (Tables 1 to 5), and explicitly presented for each FSM in Table 6. For example, the MRC is an Impact measure, but overlaps with both the Activity and Disability measures.

OPEN IN VIEWER

Table 2.

Description and psychometric properties of daily activity measures.

Measure	Activities (#)Self-/rater-administered	Rating of activities	Time to complete (minutes)# items	Time frame	Validity	Reliability	Responsiveness and MCID	Comments
Community Healthy Activities Model Program for Seniors (CHAMPS) 25	41SARA	Frequency (f)Times/weekHours/week (used to calculate energy exp.)Unable to perform optionFour Scores1. METS/week All act2. METS/week Moderate act3. f/week All act4. f/week Moderate act	10–15 minutes41 items	Typical week in past 4 weeks.	Content 70 Construct 70,71 Discriminant 70, 71	Test–retest @ 2 weeks by mail Moderate act r = 0.96 All act r = 0.62 71 ICC = Moderate act 0.67 All act 0.66 over 6 months 70 @ 2 weeks Moderate = 0.76, All = 0.62 71	Responsive 25,70 MCID = NA	A measure of physical activity to change behavior in older adults Present list of activities, evaluate for f and duration METS estimated for each act Many act geared to older, healthy adults (e.g. golf, jogging) Change in scores not associated with change in SF-36 PF 25 Limited testing and use in COPD
Canadian Occupational PerformanceMeasure (COPM) 19	9RA	Rating 1–101 = not able to do/not satisfied at all to 10 = able to do/extremely satisfied.Scores on Performance and Satisfaction TS = 1–10	10–20 minutes15 items	Current	Content 19 Construct 72	Test–retest r = 0.63 satisfaction r = 0.84 performance 73 ICC =0.81 for satisfaction 0.76 for performance 74	Responsive to pulmonary rehabilitation 74 –76 Not responsive to OT intervention 77 MCID = 2 points 78	Developed for occupational therapists to detect changes in domestic function Five-step process, for example, identify difficult activity, rate its importance, satisfaction with performance, and so on. Domains: self-care, productivity and leisure. Weighted scoring May not be responsive to all interventions
Duke Activity Status Index (DASI) 27	12SA	Yes/NoScores are weighted based on METS of activityScoring = 0 to 58.2 (best)	3 minutes12 items	Current	Construct 79 Concurrent 27 Discriminant 80	Test–retestICC = 0.95 81 Internal consistency (in heart failure) α = 0.86 79	NA	Developed to measure functional capacity in cardiovascular patients Limited use and testing in COPD Weighted scoring
Functional Performance Inventory (FPI) 32	65SA	Degree of difficulty1 = none, 2 = some, 3 = much, 4 = don’t do due to health TS = 0–3(high scores better health, due to reverse scoring)	20 minutes85 items	Current	Content 32,33 Construct 32 Concurrent 32,82,83	Test–retestICC = 0.87 32 Internal consistency α = 0.92 84 and 0.93 83	NA	Developed to assess level of difficulty with activity in COPD Subscales: body care, housework, exercise, recreation, social and spiritual NA option if don’t do activity for reasons other than health Reverse scoring
Functional Performance Inventory Short Form (FPI-SF) 33	32SA	Difficulty: 0 = don’t perform due to health or choose not to do, 1 = much difficulty, 2 = some, 3 = none TS = 0–3 (the mean of 6 subscales)(low scores better health)	10 minutesNA	Current	Content 33,83 Construct 83 Concurrent 83 Discriminant 83	Test–retestICC = TS 0.88 83 0.93 at 2 weeks 85 Internal consistency TS α = 0.93 83 α = 0.89 85	NA	Developed to assess level of difficulty with activities in COPD Subscales unchanged from FPI Rate activity as 0 if don’t perform due to health reason or choose not to do. NA option if don’t do activity for reasons other than health Scoring differs from FPI
Human Activity Profile* (HAP) 37 Formerly called Additive Activities Profile Test	94 (activity)8 (dyspnea)SA	Act = still doing, stopped doing, never did activity Dysp = none, yes a little, yes noticeable, yes severeScores:MAS—maximum act scoreAAS—adjusted act scoresScoring: 0–94 (high scores, higher function)	5–7 minutes102 items	Current	Content 86 Concurrent 86 Criterion 86	Test–retest5–14 daysMAS r = 0.76AAS r = 0.79 87 @ 2 weeksMAS r = 0.97AAS r = 0.97 88 ICC = MAS 0.76, AAS 0.87 87 Internal consistency α = 0.84 37	Responsive to PR 89 MCID = 8.4 37 MAS = 7.8AAS = 6.8 90	Developed to evaluate energy expenditure for COPD patients in PR Domains: activity and dyspnea with 4 subscales: self-care, personal/housework, entertainment/social, and independent exercise SF-36PF and MAS r = −0.63 AAS r = −0.70 88 VO2 and MAS ρ = 0.76 AAS ρ = 0.85, p < 0.05 87 6MWD and MAS = 0.45 AAS = 0.61 (both p < 0.01) 89 Limited use and testing in COPD since its development overlaps with Impact Measures
Milken ADL Scale (MAS) 48	47SA	5-point scale on ability (1 = unable to, 5 = able to do) as “prior to surgery”3-point scale on necessity.Scoring = ability 47–235 necessity 47–141Integrated score 47–705	10 minutes47 items	current	Content 48 Construct 48 Concurrent 48,91 Criterion 48	Test–retest at 2–7 days, r = 0.91 48 ICC 0.77 91 Internal consistency α = 0.96 91	Responsive to PR (only for housecleaning and other tasks) 76 MCID = NA	Developed to measure upper extremity disability Six sections representing clusters of tasks = meal preparation, personal hygiene, dressing, object manipulation, housecleaning, and other.
Stanford 7-Day Physical Activity Recall (PAR) 63 (AKA Modified Activity Recall Questionnaire (MARQ))	4RA	Identify time spent in sleep and activities for 7 days.Scoring:Total EE score (kcal/kg/day)Time spent in moderate act	20 minutes71 items	Past 7 days	Concurrent 92 In COPDDiscriminant 93 Predictive 93	Test–retest 14 days 94 Total EE r = 0.67 vigorous act r = 0.83 moderate act r = 0.75 94 NA in COPD	NATEE SWA (r = 50.83, p < 0.001).≥3 METs correlated significantly with SWA-derived time o3 METs (r = 0.54, p < 0.001) and with SWA-derived PAL r = 0.46, p = 0.002 93	Developed to assess healthy people Domains: leisure and occupational activities Estimates individual’s time spent in physical activity by category of METS (moderate, hard, and very hard) Reliability predominantly done in young, healthy Accel. time spent in >3 METS r = 0.83, p < 0.001 <3 METS p ≥ 0.05 93 Weak assessing activity level at individual level, but potential for stratifying COPD according to activity levels 93
Physical Activity Scale for the Elderly (PASE) 55	12SA	Frequency and durationTS a two-step process1. Time (hours/week) in each activity2. Weighting of each activityScoring: 0–361 (high scores high act level)	5 minutes19 items	Past 7 days	Construct 55,71 Discriminant 71	Test–retest 3–7 weeks r = 0.75 55 At 5 days r = 0.75 95 Internal consistency α = 0.69 55	NA	Measures physical activity in the elderly Domains: leisure, household, and occupational Many (8/12) sports and household activities PASE and VO2 r = 0.56, p < 0.01 96 6MWD r = 0.68, p < 0.01 71 SF36 PF r = 0.30 p < 0.01 71 Accel r = 0.19 p > 0.05 93 Cutoff of <11 for sedentary act, TS 95 Limited use and testing in COPD Weighted scores
Pulmonary Functional Status Scale (PFSS) 57	22SA	Rating varies with questions (e.g. difficulty, yes/no, blocks, frequency, independent, etc.) Scoring mean of each scale (9–34), high scores better function	15 minutes56 items	Current, past week, past month	Content 57	Internal consistency α = 0.83 57	Responsive to PR 97 MCID = NA	Developed as a disease-specific outcome measure of older adults with chronic lung disease. 3 subscales: daily activities/social, psychologic, and sexual functioning Weighted and reverse scoring
Pulmonary Functional Status Scale(modified) (PFSS-modified) 57,98	18SA	Scoring (1–15) with high scores better function	NA35 items	Current,past week, month	Construct 98 Concurrent 98	Test–retest r = 0.67 57 Internal Consistency α = 0.93 57	Responsive to PR 99 MCID=NA	PFSS reduced from 56 to 35 items Domains unchanged Weighted and reverse scoring
Pulmonary Functional Status and Dyspnea Questionnaire* (PFSDQ) 59	79 activities act (79) dysp (79)SA	Act: 0 = as active as ever to 10 = omitted entirely due to breathing Dysp: 0 = none to 10 = extreme dysp Act and dysp TS = 0–790 on eachAct and dyspMean = 0–10dysp has five stand-alone scores for f and intensity	15mins164 items	Current	Content 59 Construct 59 Discriminant 59	Internal Consistency α = 0.88–0.92 60	Responsive 59 MCID TS = 10	Developed to evaluate changes in activity and dyspnea levels and dyspnea in COPD Activities (79) evaluated for participation and 79 for impact of dyspnea Option to check if never performed the activity PFSDQ act and 6MWD Spearman p = 0.42; PFSDQ dysp p = 0.47, p < 0.001 35 Dyspnea scale overlaps with Impact Measures
Pulmonary Functional Status and Dyspnea Questionnaire (modified version)* (PFSDQ-M) 60	10 activitiesAct (10)Dysp (15)Fat (15)SA	Three domains (act, dysp, fat) act: 0 = as active as ever to 10 = omitted entirely due to breathing dysp/fat 0 = none 10 = extreme For each domain reportTS = 0–100Mean = 0–10	7 minutes40 items	Current	Construct 60,100	Test–retest 2 weeks act = 0.70 Dysp = 0.83 fat = 0.79 60 ICC= act = 0.79 dysp and fat = 0.77 at 1 week. 101 act = 0.90 dysp = 0.93 fat = 0.92 at 2 days 100 Internal consistency α = act 0.93;dysp and fat α = 0.95 60 with arm act α = 0.87all act α = 0.93 102	Responsive to PR 101,103 –105 MCID = 5 each component 101	Modified from PFSDQ to reduce # activities and measure fatigue. PFSDQ-M act and 6MWD r = 0.34, p < 0.01 106 r = −0.30, p < 0.001 101 PFSDQ-M act and CRQ dysp r = −0.32, p < 0.001 101 PFSDQ-M act and SGRQ act r = 0.76, p < 0.0001 100 6–8 grade reading level Dysp and fat domains overlap with Impact Measure
PROActive Questionnaire* 56	4SA	5 ratings; none at all to all the time rarely, sometimes, frequently and all the time.Scoring: NA	NA12 items	Past 7 days	Content 56 Construct 1 Convergent 1	Test–retestICC ≥ 0.90 1 Internal consistency α ≥ 0.80 1	NA	Developed to evaluate the impact of disease on activities Measures amount and difficulty with activities. Several activities relate to symptoms Newly developed measure, still undergoing psychometric testing 8–9-year-old reading level Overlap with Impact Measure
The Valued Life Activities (VLA) 64,107	28 act in COPD versionSA	0–3 rating0 = no difficulty 3 = unable to do.TS0–1.0or0–100%Sub scores for-obligatory-committed-discretionary activities	NA	Current	Content 64 Predictive 108 Discriminant 109	Internal consistency on 13 domains (arthritis) α = 0.63–0.88 110 Controls α = 0.60–0.86 110	NA	Developed to evaluate the impact of arthritis by assessing disability based on personal values 3 subscales (# act) obligatory (6), committed (9), discretionary (13) Rate act perform or don’t perform due to respiratory condition Then rate difficulty with performance Limited testing and use in COPD
Yale Physician Activity Survey (YPAS) 67	27RA	Summary indices:-Total time/each act-EE (kcal/week); -act dimension (on 5 act)	20 minutes27 items	Typical week in past month	Construct 67 Convergent weak 111	Test–retest14 dayTotal time r = 0.57;EE r = 0.58 act r = 0.65 67	NA	Developed to measure activity in healthy older adults Activities; work (10 act), yardwork (3 act), caretaking (2 act), exercise (5 act), recreation (7 act) 2 sections to develop 8 indices to determine vigorous, act, low intensity general movement, and time in recreation act May be useful screen of sedentary activities 111 EE and 6MWT r = 0.58, p < 0.01 EE and SF36 PF r = 0.31, p < 0.01; accel r = 0.61, p < 0.01 71 Limited use and testing in COPD Weighted scoring Scoring may be cumbersome
Zutphen Physical Activity Questionnaire (ZPAQ) 68	27SA	Yes/no, duration, normal, fast, calmScoring: time converted to minute/week for each act. Total weekly minutes and % contribution to total are calculated.Calculate time in light, mod, and heavy act.	15mins29 items	Past week or month (varies with question)	Concurrent 112	Test–retest r = 0.87 113	NA	Developed to evaluate men longitudinally born 1900-1920. Mets calculated in response to intensity, duration of exercise 7/27 act relate to sports or biking Insensitive to extremely inactive patients 112 Scoring may be cumbersome

MCID: minimal clinically important difference; SA: self-administered; RA: rater-administered; NA: not available; ICC: intra class coefficient; METS: metabolic equivalent units; COPD: chronic obstructive pulmonary disease; TS: total score; act: activities; dysp: dyspnea; PR: pulmonary rehabilitation; VO₂: oxygen consumption; PF: physical function; EE: energy expenditure; Accel: accelerometer.

* Overlap with another category.

OPEN IN VIEWER

Table 3.

Description and psychometric properties of impact measures.

Measure	Activities (#)Self-/rater- administered	Rating of activities	Time to complete (minutes)# items	Time frame	Validity	Reliability	Responsiveness and MCID	Comments
Baseline Dyspnea Index/Transitional Dyspnea Index* (BDI/TDI) 18	Variable #3 categories: magnitude of impairment, effort, and taskRASA	Levels of severity 0–4 (0 = most severe)Scores summed for each categoryBDI TS = 0–12TDI 7 points from−3 to +3 (major improvement),TDI TS = −9 to +9 (0 = no change, +9 = improved)	4–5 minutes3 items	Current	Concurrent 114	Test–retest r = 0.76 114 ICC = 0.90 115 Internal consistency α = 0.80 114	Responsive to PR 116 Responsive to treatment 117 MCIDTDI = 1 unit 117	Developed to assess dyspnea in COPD Initial assessment with BDI, follow-up with TDI for change score BDI and OCD r = 0.67, p < 0.01 118 BDI and 6MWD r = −0.02, p > 0.05 118 r = 0.54, p < 0.001 119 Overlap with Activity Measure
London Chest Activity of Daily Living scale* (LCADL) 41	15SA	0 = wouldn’t do anyway 1 = no breathlessness 2 = moderate 3 = very breathless 4 = can no longer do 5 = need someone else to do TS = 0–75	<5 minutes(estimate)15 items	Past few days	Content 41 Construct 41 Concurrent 41,120 Discriminant 121 Convergent 120 LCADL	Test–retest ICC = 0.96Internal consistency α = 0.98 41 and 0.90 120	Responsive to PR 103,122 MCID = 4 points 123 Self-care = 0.9Domestic = 2.6Physical = 0.4Leisure = 0.6 123	Developed to measure dyspnea with routine activities in COPD Domains: self-care, domestic, physical activity, leisure 20% ceiling effect on domestic domain 120 CRQ dysp r = 0.56, p < 0.001 120 Ped r = −0.50, p < 0.01 121 Numerical rating scale @ rest r = 0.25, p < 0.05 120 Overlap with Activity Measure
Medical Research Council* (MRC) 124	3RASA	Grade 0–4Score 0–4 (0 = no impairment)Also reported as grade 1–5 (1 = no impairment)	1 minute1 item	Current	Content 124 Discriminant 47,125	Test–retestICC0.82 115 0.83 103	Responsiveness is variable for PR 103,126 MCID = 1 point 126	Developed to study respiratory epidemiology. The MRC grading of dyspnea is one segment of a larger questionnaire of 17 questions on symptoms 4/5 activities relate to walking due to breathlessness. BDI r = −0.56, p < 0.05 118 6MWD r = 0.52, p < 0.001 119 Poor response to PR may be due to baseline MRC grade. 127 MRC ≥ 3 sensitive to severe physical activity Overlap with Activity and Disability Measures
Oxygen Cost Diagram* (OCD) 53	13RASA	0–10 cm vertical line (sleeping to dyspnea with brisk walking uphill). Mark line at point become dyspneic.Activities listed reflect progressive increase in energy expenditureScore in cm from 0–10 Ability score is distance (cm) from 0 to point marked.	1 minute1 item	Current	Concurrent 53,118 Construct 119	Test–retest r = 0.64	Responsiveness unclear 128,129 MCID = NA	Developed to evaluate level of breathlessness based on the incremental energy expenditure of walking and household activities Scaling based on oxygen requirements of activities OCD and 6MWD r = 0.65, p < 0.001 130 r = 0.52, p < 0.001 119 r = 0.20, p > 0.05 118 OCD and MRC r = −0.54 (0.05 > p < 0.1) 118 OCD and BDI r = 0.67, p < 0.01 r = 0.56, p < 0.05 118 Overlaps with Activity Measure
University of California San Diego Shortness of Breath Questionnaire (UCSD SOBQ)*66	21SA	0 = not at all breathless 5 = maximum/unable to do activity Scores summed,TS 0–120, high scores worse	5 minutes(estimate)24 items	Average over past week	Content 66 Construct 114	Test–retest r = 0.94 114 ICC = 0.95 115 Internal consistency α = 0.91 114	Responsive to PR 131 MCID = 5 points 132	Developed to assess severity of dyspnea with act in PR programs Dyspnea rating also on activity related to fear Overlaps with Activity Measure

MCID: minimal clinically important difference; SA: self-administered; RA: rater-administered; ICC: intra class coefficient; PR: pulmonary rehabilitation; NA: not available; Ped: pedometer.

*Indicate the instrument overlapped with another category.

OPEN IN VIEWER

Table 4.

Description and psychometric properties of subscales of surrogate measures.^*

Measure	Activities (#)Self-/rater-administered	Rating of activities	Time to complete (minutes)# items	Time frame	Validity	Reliability	Responsiveness and MCID	Comments
Clinical COPD Questionnaire* (CCQ) 23	5RASA	Rating = 0 (never/not limited) to 6 (almost all the time/totally limited). Low scores better healthSymptom 0–6Function 0–6Mental 0–6TS 0–6	2 minutes10 items	Past 7 days	Content 23 Convergent 133 Concurrent 134	Test–retest (2 weeks)ICC = 0.94 23 Internal consistency α = 0.91 23 function = 0.77 133 and 0.94 134	Responsive to smoking cessation 23 PR 135 and exacerbations 134 MCID = 0.4 136 0.4 with PR 135,137 CCQsx = 0.5CCQfs = 0.6CCQmental = 0.7 137	Developed to measure health status in COPD Domains: symptoms, functional and mental states. Functional evaluates 4 act Overlaps with Activity and Impact Measures
Chronic Respiratory Disease Questionnaire* (CRQ) 21 CRDQ and CRQ used interchangeablyCRQ-IA investigator-administeredCRQ-IA = RA and dysp act individualized CRQ-SR (self-reported)CRQ-SAS 138 = SA and dysp act standardized CRQ-SA = SA (user needs to check how dysp act determined)	5RASA	Dysp domain0 = extremely dyspneic to 7 = not at all.Other domains1 = maximum to 7 = no impairment Scores: Dysp 1–7 Fat 1–7 Emo 1–7 Mastery 1–7TS= 20–140	5–10 minutes20 items	Past 2 weeks	Content 21,22	Test–retestICC = 0.83 dysp on CRQ-SA 139 0.73–0.95 140 CRQdysp α = 0.91 141 α = 0.90 133 α = 0.53 142 α = 0.53–0.84 140	Dysp domain has variable response to PR 143 –146 MCID = on CRQ-IA, dysp and TS = 5 147 CRQdysp = 5TS = 10 101 dysp = 0.5 fat = 0.5 emotion = 0.4 mast = 0.4per item 138	Developed to determine the frequency and importance of areas of dysfunction in resp patients. Domains: dysp, fat, emo function, and mastery Dysp domain and symptom of SGRQ r = 0.46 CRQ-SAS act relate to emotions, basic needs, walking, chores, and social 138 Patients don’t often select same act to evaluate dysp on posttest with CRQ-individualized 139 CRQdysp and SGRQsx r = 0.46, p < 0.01 141 TS not well tested 140 Overlaps with Activity and Impact Measures
EuroQol* (EQ-5D-5 L) 28,29 EQ VAS	3SARA1	Rating of each activity/dimension on 5 levels of severity: no problem to extreme problems.Ratings converted to Index Value of 0–1Rating0 = worse imaginable health 100 = best imaginable health Scoring 0–100 on vertical 20 cm VAS	5 minutes(estimate)5 items1 minute1 item	TodayToday	Content 28 Construct 29,148 Discriminant 149 Convergent 148	Test–retestκ 95% CI 0.69 mobility, 0.64 activity 148 ICC 0.75 148 NA	Responsive to PR 149 MCID = 0.05 149 MCID = 7 149	Measure of health status 2 parts, the EQ-5D-5 L and EQ VAS Act/dimension: mobility, self-care, usual act, pain/discomfort, anxiety/depression Scoring does not separate act from emotion and pain rating Relation to SGRQ act r = −0.60, p < 0.001; CRQdys r = 0.40, p < 0.001; CCQFunc r = −0.67, p < 0.001 149 Weighted scoring Overlaps with Activity Measure
St. George’s Respiratory Questionnaire* (SGRQ) 61	14on activity domainSA	Scoring each domain 0–100TS = 0–100(high scores worse)	10 minutes56 items	Current and past 4 weeks	Content 61 Construct 61,150	Test–retest (2 weeks)ICC = total score 0.92 and 0.87 on activity domain 61 Internal consistency α = 0.83 activity 151	Responsive to:PR 103,131 exacerbations 146,152 and pharmacology tx 153 MCID = 4 points per domain and 7 with PR 137 IPF sx = 8 act = 5 impact = 7TS = 7 154	Developed to measure health status in respiratory patients Domains: act, symp, impact TS 6MWD r = −0.56, p < 0.001 35 Items are weighted Overlaps with Activity and Impact Measures
Medical OutcomesStudy* (SF-36) 62	10 on Physical Function scaleSA	Limited a lot, a little, not limited at all on activityTS = 0–100(low more limitation)	5–10 minutes36 items	Current	Content 69 Construct 69,155,156	Test–retest ≥0.90 physical scale 155	PCS responsive to PR 131 MCIDILD 3–5 154	Developed to survey health Scales (8): physical, social, mental health, vitality, pain, general health, and so on Physical function scale and physical component score (PCS) often used for comparison as physical function standard PCSs are scores from PF, role physical, pain, and general health Overlaps with Activity Measure

COPD: chronic obstructive pulmonary disease; MCID: minimal clinically important difference; SA: self-administered; RA: rater-administered; ICC: intra class coefficient; PR: pulmonary rehabilitation; act: activities; dysp: dyspnea; VAS: visual analog scale; CI: confidence interval; NA: not available; TS: total score; ILD: interstitial lung disease; PCS: physical component score; PF: physical function

* Overlap with another category. The domains representing activity levels (e.g. dyspnea, physical function) were reported: CRQ: dyspnea; CCQ: functional state; SGRQ: activity; SF36: physical function scales.

OPEN IN VIEWER

Table 5.

Description and psychometric properties of protocol/performance-based measures.

Measure	Activities (#)Self-/rater-administered	Rating of activities	Time to complete (minutes)	Time frame	Validity	Reliability	Responsiveness and MCID	Comments
Glittre-ADL Test 35	4RA	4 activities constituting a “lap”Scoring: time spent to complete laps in minutes	<10 minutes4 items	Current	Content 35 Concurrent 35 Discriminant 157,158	Test–retest @24 hours = 0.93 35	Responsive to pulmonary rehabilitation 35 MCID = NA	Developed to measure functional status in COPD with standardized ADL-like activities Backpack (2.5 kg/women, 5 kg/ men) carried during activity Complete 5 laps as fast as possible, rest if needed 6MWD r = −0.82, p < 0.001 35 r = −0.87, p < 0.01 159 VO2 r = 0.87, p < 0.05 159 May not be responsive to upper extremity exercise 76
Londrina Activity of Daily Living Protocol (LAP) 43	5RA	Total seconds to complete 5 tasks	7 minutes5 items	Current	Content 43 Concurrent 43,160	ICC =>0.94 43 0.91 160	NA	Developed to assess upper and lower extremities and trunk activities Assesses ADL performance in COPD 5 stations demonstrating upper, lower extremity, trunk flexion/rotation/ inclination Complete at own pace, rest as needed 6MWD r = −0.53 160
Monitored Functional Task Evaluation (MFTE) 50	5	5 tasks each done within 2 minutes.Scoring 0–4 each taskScoring 0–20 for overall performance	15–20 minutes5 items	Current	Content 50 Concurrent 50	Test–retestICC = 0.82 50	Responsive to qigong added to PR 161 MCID = NA	Developed to evaluate physical components contributing to occupational performance in COPD with moderate–severe disease 5 tasks: walk, sit–stand, lift, walk carrying load Done at usual pace Scores transformed 6MWD r = 0.32, p ≤ 0.01 50 CRQdysp r = 0.18, p > 0.05 50 Limited testing in COPD

MCID: minimal clinically important difference; NA: not available; COPD: chronic obstructive pulmonary disease; ICC: intra class coefficient; RA: rater-administered.

OPEN IN VIEWER

Table 6.

Description and psychometric properties of disability-based measures.

Measure	Activities (#)Self-/rater-administered	Rating of activities	Time to complete (minutes)# items	Time frame	Validity	Reliability	Responsiveness and MCID	Comments
Barthel Index (BI) 16	10SARA	Rating varies with item and study (0, 5; 0, 5, 10; and 0, 5, 10, 15):0 = dependent 10 or 15= independent TS = 0–100Alternative rating and scoringRating 0, 1, or 2TS = 0–20 162	<5 minutes SA20 minutes RA10 items	Current	Concurrent 163 Discriminant with pneumonia 164	NA in COPD.Test–retest:Interrater:Coefficient of concordance W = 0.93 162 Internal consistency α = 0.87 17	Responsiveness not available in COPDMCID = 4.02 pts. In chronic stroke 165 NA in COPD	Developed to evaluate independence in frail elderly and stroke NEADL has greater sensitivity (76% vs 19%) than Barthel 4 for differentiating elderly with respiratory disability BI and MRC r = 0.53, p < 0.001 163 Good psychometrics among acute and chronic stroke Limited testing and use in COPD
BI modified (BIM) 17	10SA	Coding of original act as 1–5TS = 0–100	<510	Current	NA	Internal consistency α = 0.90 17	NA respiratory patients	Modified scoring metric 0–4 = very severely disabled 5–9 = severely 10–14 = moderately 15–19 = mildly disabled 20 = independent Items are weighted No known use in COPD
Groningen Activity Restriction Scale (GARS) 36	18SA	4-point scale1 = can do independently without difficulty 2 = independent, some difficulty 3 = independent, great difficulty 4 = cannot do independently (with or without help)Scores 18–72 (max disability)	NA18 items	Past week	Content 36 Construct 36 Concurrent 36,166 Discriminant 36	Internal consistency α = 0.94 167	NA	Developed to assess disability in domains of personal care and domestic activities Activities: grooming, feeding self GARS and 6MWD r = 0.77 168 r = 0.53 with steps 166 GARS and SF36 PF r = 0.48, p < 0.01 CCQ Funct r = −0.51, p < 0.01 SGRQ act r = −0.57, p < 0.01 166 If don’t engage in act, asked to “imagine” if they could
Manchester Respiratory Activity of Daily Living Questionnaire (MRADL) 44	21SA	Ability to perform0 = not at all or with help 1 = alone with difficulty or alone easily Scoring 0–21 (no impairment)	10 minutes21 items	Current	Discriminant 44	Test–retestICC 0.92 and 0.86 169 mailed 2 weeks apartInternal consistency α = 0.91 169	Responsive to PR 44 MCID NA	Developed to evaluate disability in elderly with COPD Domains: mobility, kitchen, domestic tasks, and leisure Limited testing
Nottingham Extended Activities of Daily Living Questionnaire (NEADL) 3	22SA	Rate performance from 0 = not perform or with help 1 = on my own with difficulty or on my own Score 0–22 (high score, more independent)	<10 minutes22 items	Past week	Content 3 Concurrent 170 Discriminant 4,47	Test–retestReliabilityκ coefficient 0.83–1.00 (mailed 2 weeks apart) 3 ICC 0.89 171	ResponsivenessNot tested in COPDMCID = 6.0 171	Developed to assess stroke patients via mail Sections: mobility, kitchen, domestic, and leisure activity Greater sensitivity than Barthel 4 Limited use and testing in COPD

MCID: minimal clinically important difference; SA: self-administered; RA: rater-administered; TS: total score; NA: not available; COPD: chronic obstructive pulmonary disease; ICC: intra class coefficient.

OPEN IN VIEWER

Table 7.

Listing of FSMs by categories and identifying categories with which they overlap(X).

Measuresa	Categories
	ACT	IMP	SURR	DIS	PB
Activity (ACT)
CHAMPS 25
COPM 73
DASI 27
FPI 32
FPI-SF 33
HAP 37		X
MAS 48
PAR 63
PASE 55
PFSS 57		X
PFSS-35 57		X
PFSDQ 59		X
PFSDQ-M 60		X
ProActive 56		X
VLA 64
YPAS 67
ZPAQ 68
Impact (IMP)
BDI 18	X
LCADL 41	X
MRC 46	X			X
OCD 53	X
SOBQ 66	X
	Categories
Measuresa	ACT	IMP	SURR	PB	DIS
Surrogate (SURR)
CCQ 23	X	X
CRQ 21	X	X
EuroQOL-ED 5D-5 L 28	X
SGRQ 61	X	X
SF-36 62	X
Performance-Based (PB)
Glittre Test 35
LAP 43
MFTE 50
Disability (DIS)
BI 16
BIM 17
GARS 36
MRADL 44
NEADL 3

FSM: functional status measure. Shaded columns indicate the activities within the respective categories.

^a Refer to Table 1 for abbreviations of FSMs.

Discussion

This review of the literature has identified a diverse range of measures available to the clinician evaluating functional status for people with COPD. This diversity likely reflects the numerous reasons why functional status is measured for people with COPD in the clinical and research objectives. Considering the diversity of measures available for use, selection must be thoughtful based on the nature of the population being studied, and evaluation being conducted, not simply used because it is a standard at the institution. The options are varied and may be overwhelming. Through categorizing the FSMs and providing a summary of design and psychometric properties of the measures, this article aims to guide clinicians and researchers alike in the selection of the most appropriate measure for their situation.

While measuring functional status is a complex construct, not all measures could be easily categorized into one theme. We found measures that overlap between categories. Further, some aspects of FSMs may not be considered “activity measures” by some. For example, the chronic respiratory disease questionnaire (CRQ) ²² dyspnea domain can be considered an “impact” measure, as this most closely measures function in the CRQ (see Surrogate category). On the other hand, the Saint George’s Respiratory Questionnaire (SGRQ), ⁶¹ also a health status measure, has an “activity” as well as a symptom domain. However, this domain queries about many symptoms, not only dyspnea with an activity. Arguably, the dyspnea domain of the CRQ could be an Impact-Based Measure because it asks patients to rate the severity of their dyspnea with each activity. However, because it is a subscale of the CRQ, we determined it best fit with other Surrogate Measures. On the other hand, the Medical Research Council Modified version (mMRC) with 5 grades (0–4) ^46,172 has been used as both a measure of dyspnea and disability. ^47,95 While more commonly known as a dyspnea measure, the mMRC evaluates the impact of dyspnea on activity levels (primarily walking) and therefore meets our criteria for an Impact-Based Measure. However, the mMRC could also arguably be justified as a disability measure because the grades provide a distinct indication of impairment, that is, activity limitation (breathlessness only with strenuous exercise) to severe limitation (too breathless to leave the home). In interpreting the categorization, clinicians and researchers therefore may select an FSM based on the overlap. This could be of particular use when more than one domain or construct is to be measured, saving patients time in completing only one tool instead of multiple. While the creation of this framework and categorization of FSMs has attempted to simplify selection of instruments, extensive consideration by clinicians and researchers alike is still needed prior to selection of an FSM to ensure that the most efficient and targeted tool is indeed selected.

Psychometric testing is a critical feature to a strong instrument and issues of reliability, validity, and responsiveness should have been demonstrated, and through this review a summary of these properties has been synthesized for clinicians to access. Where psychometric properties of an instrument are not available in the literature, further research should be completed prior to clinical application of the tool. The framework presented in this article provides information only on tools that have been assessed, and therefore, this article is intended as one of many resources for clinicians to draw on.

The available FSMs to date have predominantly been developed and evaluated in English language countries with European-based cultures, and this should be considered when selecting a measure. Some activities identified in the original development of the instruments may not be relevant for some countries/cultures/genders/age groups. For example, FSMs containing activities such as soccer, shoveling snow, and ice skating may not be relevant to certain areas of the world or to the elderly individual with moderate to severe disease. Further, some instruments used gender-specific terms or stereotypes to describe activities. This may result in significant missing data. In the development of an instrument, there should be virtually no missing data (i.e. the instrument must make allowances for activities never performed, unrelated to COPD). On the other hand, if a study finds missing data occurring, they should be vigilant for the reasons for lack of response. For culturally responsive and adaptable health-care practice, ethnocultural interpretation of the measures should be evaluated prior to selection for application, and research into application of the FSMs to broader diverse communities is needed.

In evaluation of reading level of FSMs included in this review, most instruments attempt to attain reading at the 5th or 6th grade reading level (although not always stated); however, the nature of terms used in health care (e.g. breathlessness) may result in higher than desirable reading levels and may impact the psychometric properties of the FSMs. Understanding the reading and health literacy of the population group should also be a factor in selecting an instrument. Health literacy is the level to which an individual has the capacity to obtain, process, and understand basic health information and health-care services available to make informed decisions on health-care management. ¹⁷³ Low levels of health literacy are readily reported for people with COPD and are linked to poorer health outcomes. ^{174 –176} Cognitive capacity may also impact the ability to complete the FSM. The incidence of cognitive impairment for people with COPD is greater than the general population with structural brain abnormalities, such as decreased hippocampal volume, ¹⁷⁷ increased deep or infratentorial microbleeds, ¹⁷⁸ and white matter lesions, ¹⁷⁹ being more frequently evident. When measuring functional status, should the patient’s reading, cognitive, and literacy level be below that required, this could significantly impact the psychometric properties of the tool and lead to inaccurate information and conclusions. Further, research in understanding the impact of reading or literacy levels on the psychometric properties of FSMs is warranted to ensure that the tools are valid and reliable across different cultural groups.

Conclusions

A diverse range of measures are available to the clinician and researcher looking to evaluate functional status for people with COPD. The establishment of the many FSMs is likely related to the numerous reasons for why functional status is measured for people with COPD. Considering the diversity of measures available for use, selection must be thoughtful based on the nature of the population being studied, and evaluation being conducted, not simply because it is a standard at the institution. Psychometric testing is a critical feature to a strong instrument and issues of reliability, validity, and responsiveness need to be understood prior to measurement use. Contextual nature of measures such as language used and activities measured is also important. One approach to categorizing FSMs was presented to include daily activities measures, impact measures, surrogate measures, indirect performance-based measures, and disability-based measures. A summary of design and psychometric properties of the measures was provided as a guide to clinicians and researchers in the selection of the most appropriate application of a measure.