Reliability and Validity of the Turkish Version of the Modified Dynamic Gait Index in the Elderly

Abstract

The modified Dynamic Gait Index (mDGI) is one of the valid instruments used in the evaluation of gait disorders. This study aimed to translate the mDGI into Turkish and evaluate the evidence for its reliability and validity for use in an elderly population. For test-retest reliability, the mDGI was administered twice, and for inter-rater reliability, the mDGI was administered alone on the same day by two raters. Concurrent validity of the mDGI was assessed using Pearson’s correlation analysis between the Turkish version of the mDGI score and the Timed Up and Go (TUG), Berg Balance Scale (BBS), and 10-m Walk Test (10-MWT), respectively. The internal consistency of the mDGI was found to be excellent (Cronbach’s alpha = 0.97) and test-retest (ICC = 0.95; 95% Cl (0.84–0.95)) and inter-rater reliability (ICC = 0.95; 95% Cl (0.85–0.95)) were excellent. A negative, moderate correlation was found between mDGI and TUG (r = −0.73, p < .0001), and a positive, moderate correlation with BBS (r = 0.71, p < .0001) and 10-MWT (r = 0.72, p < .0001). The Turkish version of the mDGI was found to be a valid and reliable assessment instrument for gait and balance in the elderly.

Keywords

Balance elderly falls gait modified dynamic gait index reliability validity

Introduction

Gait disorders are common in the elderly population and may occur due to age-related physical and physiological changes or as a result of comorbidities (Duque, 2016). Approximately 28–35% of people aged ≥65 years fall each year due to gait impairment, and this rate rises to 32–42% in those aged >70 years (Organization et al., 2008). Although there are many factors that can cause falls in older adults, a number of assessment methods have been developed that can reasonably measure the risk of falls (Berg & Cassells, 1992).

The Dynamic Gait Index (DGI) is a widely accepted functional gait instrument used to assess the risk of falls and functional stability in the elderly while walking (Shumway-Cook et al., 2013). In many studies, the DGI has been recommended as a valid, reliable, inexpensive, and quick instrument to evaluate the gait and balance of individuals with mobility limitations (Alghwiri, 2014; Dibble & Lange, 2006; McConvey & Bennett, 2005; Simon & Harro, 2004; Wrisley et al., 2003).

Although the DGI can predict the probability of gait impairments and falls, the original version of the test had some limitations such as the scoring system and ceiling effect. Shumway-Cook et al. developed the modified version of the DGI (mDGI) to overcome these limitations. The rating scales for each of the eight DGI tasks were re-defined in the mDGI (Shumway-Cook et al., 2013). Although the DGI has been shown to be reliable and valid in different languages and populations (Alghwiri, 2014; Herman et al., 2009; Tuomela et al., 2012), very few studies have been conducted on the mDGI (Anastasi et al., 2019; Matsuda et al., 2014; Yu et al., 2020). The validity of this standardized assessment instrument, which evaluates gait and balance, has not been examined in a Turkish population. Therefore, the aim of this study was to translate the mDGI into the Turkish language and evaluate the evidence for reliability and validity of its use in an elderly population.

Methods

Participants

The study included 81 older adults living in Istanbul Bahcelievler Nursing Home Elderly Care and Rehabilitation Center. The inclusion criteria of the study were age ≥65 years and the ability to walk with/without any walking aid at a level where tests can be applied. Exclusion criteria were defined as unstable health status (e.g., serious cardiac or pulmonary problem) and cognitive and visual problems. All participants were informed about the study and consent for participation was obtained. The study was carried out in accordance with the criteria of the Helsinki Declaration.

Sample size

There is no internationally recognized consensus on the minimum sample size required for validation studies, but two to 20 participants are accepted for each item (Anthoine et al., 2014). Accordingly, given that the mDGI consisted of 8 items, it was aimed to include at least 10 subjects for each item, and therefore, a sample size of at least 80 was calculated.

Translation of the mDGI

Translation of the mDGI was performed according to the instructions provided by Beaton et al. (2000). Two physiotherapists translated the index from English to Turkish independently. The consensus translation based on these two independent translations was translated back into English by a native English speaker. The original version, back translation, and consensus translation were compared in a study group that included the original translators, English linguists, and a professor in physiotherapy. Finally, a Turkish version of the mDGI was introduced (Appendix A).

Procedures

Before the study, the raters received a briefing about the mDGI and the testing procedure. Two raters (Rater 1 and Rater 2) with experience in geriatric physiotherapy performed the inter-rater measurements. The first two assessments were applied on the same day, by the two raters (Rater 1 and Rater 2) for the inter-rater evaluation, with a 3-hour interval between the first and the second application, and the first interview with the instrument for each patient was carried out alternating the order of interviewers. The third assessment was performed 7 days later by Rater 1 (Rater 1 re-testing).

Outcome Measurements

The mDGI

The mDGI is an instrument that evaluates different walking conditions (Shumway-Cook et al., 2013). The maximum score in the original version was 24 points (range, 0 - 24), while in the mDGI it is 64 points [time (range, 0 - 24), gait pattern (range, 0 - 24), and level of assistance (range, 0 - 16)].

The Timed Up and Go Test

The Timed Up and Go (TUG) is used to evaluate the balance abilities of elderly patients. In recent studies of geriatric populations, the inter and intra-rater reliability of the TUG have been reported as high (ICC = 0.99, ICC [3,1] = 0.92–0.96, ICC [3,3] = 0.98). A shorter time is an indication of a high level of mobility (Shumway-Cook et al., 2000; Steffen et al., 2002).

The Berg Balance Scale

A 14-item The Berg Balance Scale (BBS) was used to evaluate the balance and postural control of the study participants. A high score in this test is associated with a high level of mobility. Different studies have demonstrated high inter-rater and intra-rater reliability (ICC = 0.98, ratio of variability among subjects to total 0.96–1.0) (Berg & Cassells, 1992; Shumway-Cook et al., 1997).

10-m Walk Test

In this assessment, the stopwatch was started when the patient reached the second meter and stopped when the patient reached the 12th meter. At the end of the test, gait speed was calculated by dividing the 10-meter distance by the time (s) (Bohannon, 1997).

Statistical analysis

Data obtained in the study were analyzed statistically using SPSS version 21.0 software (IBM SPSS Inc., Chicago, IL, USA). The internal consistency of the Turkish version of mDGI was measured using Cronbach’s alpha coefficient and the test-retest reliability using the intraclass correlation coefficient (ICC) (Streiner et al., 2015). The standard error of measurement (SEM) associated with the Turkish version of mDGI was calculated from the standard deviation of the test scores multiplied by the square root of (1−ICC): SEM = SD x √(1−ICC). Minimum detectable change (MDC₉₅) was then calculated as: 1.96 × SEM x √2 (De Vet et al., 2003). The concurrent validity of the mDGI was assessed using Pearson’s correlation analysis. The strength of correlation coefficients was classified as 0–0.25 (absent or very weak), 0.25–0.50 (weak), 0.50–0.75 (moderate), or 0.75–1.00 (strong) (Bewick et al., 2003). The questionnaire was considered to have a floor or ceiling effect when more than 15% of the patients had the lowest (= 0) or highest (= 64) possible score, respectively (Terwee et al., 2007). The level of statistical significance was set at p < .05.

Results

Evaluation was made of a total of 81 elderly individuals with a mean age of 73.91 ± 5.96 years and BMI of 28.14 ±6.01 kg/m². The TUG, the BBS, the 10-m Walk Test (10-MWT), and the mDGI outcome scores are presented in Additional File-Table 1.

Table 1.

Demographic and Clinical Characteristics of the Participants.

Characteristic	Mean (SD)	n (%)
Age (years)	73.91 ± 5.96
Sex (female)		48 (59.2)
Height (cm)	164.91 ± 9.22
Weight (kg)	79.42 ± 13.79
Body Mass index (kg/m²)	28.14 ± 6.01
Education duration (years)	6.89 ± 4.59
History of falling (times in the last 12 months)		21 (25.9)
SMMST (total score)	25.27 ± 4.30
TUG (sec)	10.36 ± 3.01
BBS (total score)	50.66 ± 4.23
10-MWT (m/s)	1.01 ± 0.32

Note. SMMST = Standardized Mini Mental State Test; TUG = Timed Up and Go Test; BBS = Berg Balance Scale; 10- MWT = 10- Meter Walk Test; mDGI = Modified Dynamic Gait Index; SD = Standard Deviation.

The internal consistency of mDGI was excellent (Cronbach’s alpha = 0.97). The test-retest reliability (ICC = 0.95; 95% CI (0.84–0.95)) (see Additional File-Table 2) and inter-rater reliability (ICC = 0.95; 95% Cl (0.85–0.95)) (see Additional File-Table 3) of the mDGI were excellent. The SEM values for inter-rater and intra-rater reliability were 2.9 points and 2.4 points, respectively, and the MDC₉₅ was 5.6 points.

Table 2.

Test–Retest Reliability of the mDGI Scores.

Item	1^st Assessment Mean ±SD	2^nd Assessment Mean ±SD	ICC	95% CI
1. Gait level surface	6.54 ± 1.48	6.70 ± 1.74	0.93	0.80–0.93
2. Change in gait speed	6.80 ± 1.69	6.80 ± 1.69	0.99	0.98–0.99
3. Gait with horizontal head turns	6.10 ± 1.30	6.58 ± 1.78	0.90	0.69–0.89
4. Gait witch vertical head turns	6.58 ± 1.26	6.62 ± 1.81	0.87	0.63–0.86
5. Gait and pivot turn	6.29 ± 1.50	6.37 ± 1.95	0.92	0.75–0.91
6. Step over obstacle	6.35 ± 1.81	6.50 ± 2.01	0.96	0.87–0.96
7. Step around obstacles	6.60 ± 1.34	6.66 ± 1.76	0.94	0.81–0.93
8. Steps	6.22 ± 1.81	6.39 ± 1.89	0.95	0.83–0.94
Total score	51.58 ± 10.68	51.84 ± 11.09	0.95	0.84–0.95

Note. mDGI = Modified Dynamic Gait Index; ICC = Intraclass correlation coefficient; CI = Confidence interval; SD = Standard Deviation.

Table 3.

Inter-Rater Reliability of the mDGI Scores.

Item	Rater 1 Mean ±SD	Rater 2 Mean ±SD	ICC	95% CI
1. Gait level surface	6.54 ± 1.48	6.75 ± 1.70	0.93	0.78–0.92
2. Change in gait speed	6.80 ± 1.69	6.74 ± 1.71	0.94	0.82–0.92
3. Gait with horizontal head turns	6.10 ± 1.30	6.66 ± 1.73	0.90	0.70–0.89
4. Gait witch vertical head turns	6.58 ± 1.26	6.68 ± 1.76	0.87	0.64–0.87
5. Gait and pivot turn	6.29 ± 1.50	6.43 ± 1.96	0.93	0.78–0.92
6. Step over obstacle	6.35 ± 1.81	6.50 ± 1.98	0.96	0.88–0.96
7. Step around obstacles	6.60 ± 1.34	6.69 ± 1.71	0.95	0.83–0.94
8. Steps	6.22 ± 1.81	6.37 ± 1.94	0.95	0.84–0.94
Total score	52.58 ± 12.98	52.89 ± 12.61	0.95	0.85–0.95

Note. mDGI = Modified Dynamic Gait Index; ICC = Intraclass correlation coefficient; CI = Confidence interval; SD = Standard Deviation.

A negative, moderate correlation was found between mDGI and TUG (r=-0.73, p < .0001), and a positive, moderate correlation between mDGI and BBS (r = 0.71, p < .0001), and the 10-MWT (r=0.72, p < .0001).

Of the total 81 study participants, 4 had the highest score on the Turkish version of mDGI, and none had the lowest score. Therefore, no floor or ceiling effect was found.

Discussion

The mDGI was successfully translated into the Turkish language. The Turkish version of mDGI showed excellent test-retest reliability as well as inter-rater reliability and validity in an elderly population. The SEM values for inter and intra-rater reliability were 2.9 points and 2.4 points, respectively, and the MDC₉₅ was 5.6 points. In addition, there was no floor or ceiling effect present for the Turkish version of the mDGI. Therefore, it was concluded that the mDGI was a reliable and valid instrument to assess dynamic balance in the Turkish elderly population.

Few studies have verified the validity and reliability of mDGI, and these studies have focused on demonstrating the reliability and validity of the index in large and diverse populations of patients with gait disorders (Anastasi et al., 2019; Matsuda et al., 2014). Shumway-Cook et al. (1997) reported that the reliability of the total mDGI score was 0.96 for inter-rater reliability and 0.98 for intra-rater reliability. Yu et al. (2020) reported that the inter and intra-rater reliability values of mDGI were 0.99 and 0.97, respectively in patients with vestibular disorders, and the internal consistency of the mDGI score was 0.99. In the present study, mDGI showed excellent internal consistency (ICC = 0.95) and intra-rater reliability (ICC = 0.95), similar to previous studies.

The established SEM values in the current study were 2.9 points for inter-rater reliability and 2.4 points for intra-rater reliability. In clinical practice, physiotherapist should be aware of the potential errors inherent in their clinical measurements and thorough standardization of the procedure is of the utmost importance. The MDC₉₅ for the mDGI was 5.6 points. Based on these findings, any change in score of over 6 points (out of 64) at a 95% confidence level may be viewed as a true change for the Turkish version of mDGI. In the study by Shumway-Cook et al. (2013), MDC₉₅ was found to be 4 points for the mDGI total score.

Compared to the original DGI, there are few studies in literature that have investigated the relationship between the mDGI and balance and walking parameters. Herman et al. (2009) reported that the DGI was moderately correlated with BBS (r = 0.53) and TUG (r = −0.42) in a study of an elderly population. Yu et al. (2020) reported that the mDGI scores were correlated with TUG scores (r = −0.65) in patients with a vestibular disorder. Similar to previous studies, the mDGI scores in the current study were negatively correlated with the TUG, and positively correlated with the 10-MWT and BBS scores. These findings show that a higher mDGI score indicates better dynamic balance and walking speed.

A limitation of this study is that the results cannot be generalized to all geriatric populations. In addition, the balance and mobility of the elderly participants could not be evaluated with more objective devices in laboratory settings. Although the mDGI was found to be a valid and reliable assessment tool, there is a need to determine the optimal cut-off point to determine fall risk in this population.

Conclusions

The Turkish version of the mDGI was found to be a valid and reliable assessment instrument for the evaluation of gait and balance in the elderly. In the assessment of the elderly, the mDGI is an instrument that is easy to apply and correlates with other functional gait and balance assessments. Further experimental investigations are needed to determine cut-off scores, estimate responsiveness, and the minimum clinically important difference of mDGI.

Supplemental Material

Supplemental Material - Reliability and Validity of the Turkish Version of the Modified Dynamic Gait Index in the Elderly

Supplemental Material for Reliability and Validity of the Turkish Version of the Modified Dynamic Gait Index in the Elderly by Emrah Zirek, Rustem Mustafaoglu, Aynur Cicek, Ishtiaq Ahmed, and Savvas Mavromoustakos in Evaluation & the Health Professions

Footnotes

Acknowledgments

The authors would like to thank Caroline Walker for her editing support.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Informed Consent

Informed consent was obtained from all of the participants in the study.

Ethical approval

This study was approved by the Clinical Research Ethics Committee (Approval number: 2019–06–13) and was conducted in compliance with the 1964 Declaration of Helsinki.

ORCID iD

Rustem Mustafaoglu

Supplemental Material

Supplemental material for this article is available online.

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