Test-Retest Reliability and Minimum Detectable Change of 2-Minute Walk Test among Individuals with Knee Osteoarthritis

Introduction: Two-Minute Walk Test (2MWT) is a simple, practical, and less time consuming test. Patients do not get fatigued while performing this test as a part of routine physical examination. 2MWT shows an excellent correlation with other walk tests and can be used as an alternative test in patients with multiple comorbidities. The reliability of a test is a must for its recommendation to be used in clinics as well as research. Measurement properties have been reported in different populations for 2MWT. However, no data exist for 2MWT in patients with Knee Osteoarthritis (KOA). Aim: To establish the test-retest reliability and Minimal Detectable Change (MDC) scores for the 2MWT in patients with bilateral KOA. Materials and Methods: A prospective test-retest research study designed to assess the reliability of 2MWT. Eighty-two patients with KOA (27 males and 55 females) were included in the study. Health status was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). The Numeric Pain Rating Scale (NPRS) and WOMAC were assessed on two consecutive days. Participants performed 2MWT on two different occasions with 48 hours difference in between. Both session was conducted for 45 minutes each on a 30 meter walking pathway. Data was analysed using Statistical Package for the Social Sciences (SPSS) version 20.0 for Windows (SPSS Inc., Chicago, IL, USA). Results: 2MWT showed an excellent test-retest reliability. Intraclass Correlation Coefficient (ICC) for 2MWT were 0.98. Test-retest reliability assessed by two trials of 2MWT showed 1st trial mean +/- SD of 154.33 +/- 19.59 and 2nd trial mean +/- SD of 156.69 +/- 19.68. Mean difference +/- SD between both trials was 2.36 +/- 2.74, which was statistically significant (p<0.001). The Standard Error of Measurement (SEM) and Minimal Detectable Change at 95% confidence level (MDC95) for 2MWT were 2.76 and 5.52 meters, respectively. Conclusion: The study recommends that 2MWT can be used as a test for assessing walking capacity among patients with KOA. A change of more than 5.52 meters can be considered as change-free of error. It can be used as an alternative to 6MWT in patients with KOA who cannot tolerate a higher duration/intensity walk test.