Objective

Examine the clinical validity of the Functional Performance Inventory (FPI), a new functional outcome indicator for patients with chronic obstructive pulmonary disease (COPD).

Methods

Subjects with COPD were recruited from an asthma and allergy clinic where they completed the FPI, Functional Status Questionnaire (FSQ), Duke Activity Status Index (DASI), pulmonary function tests (PFT) and 12-minute walk distance (12-MWD) test. Subjects wore a wrist actigraph to monitor physical movement over a 3-day mid-week period while they recorded their physical activities, activity difficulty, and symptoms (dyspnea, fatigue) using the NIH Activity Record (ACTRE).

Patients

Twenty-two patients (13 men, 9 women) participated in the study. Mean (± SD) age of the sample was 64 ± 10 years; forced expiratory volume in the first second (FEV₁) = 1.0 ± 0.46 L; percent of predicted FEV₁ = 37.30% ± 3.99%; and 12-MWD = 1683 ± 872 ft.

Results

FPI total score correlated significantly (p < 0.05) with percent of predicted FEV₁ (r = 0.55), 12-MWD (r = 0.52), diary data for dyspnea (r = -0.59), fatigue (r = -0.62) and difficulty with activity (r = -0.71), and FSQ basic (r = 0.61) and intermediate (r = 0.70) activities of daily living. Correlations with the DASI (r = 0.43) and actigraph (r = 0.26) were moderate, but not statistically significant. The household maintenance subscale correlated (p < 0.05) with all of the validation measures (r = 0.52 to 0.81), including the activity monitor (r = 0.52).

Conclusions

The results suggest the FPI is a valid instrument for evaluating subjective performance in COPD patients.