Reliability and minimal detectable change of the 2-minute walk test and Timed Up and Go test in patients with total hip arthroplasty

Performance-based outcome measures are becoming increasingly important in health care. The 2-minute walk test (2MWT) and the Timed Up and Go test (TUG) are frequently used in clinical trials as performance-based tests in many diseases including osteoarthritis. The purposes of this study were: (1) to determine test-retest reliability of data for the 2MWT and the TUG; (2) to determine minimal detectable change (MDC) scores for the TUG and 2MWT in patients with total hip arthroplasty (THA).

37 patients, who had undergone primary THA, were included. Patients twice performed trials for the 2MWT and TUG on the same day. In addition to demographic data of patients, the Harris Hip Score, 2MWT and TUG scores were recorded.

The TUG and 2MWT showed excellent test-retest reliability. The Intraclass correlation coefficient ICC (2,1), Standard error of measurement (SEM) and minimal detectable chance at the 95% CI (MDC₉₅) for TUG were 0.96, 0.59 seconds and 1.62 seconds respectively. The ICC (2,1), SEM and MDC₉₅ for 2MWT were 0.96, 6.37 m and 17.56 m respectively.

Clinicians and researchers can be confident that greater changes than 1.62 seconds for TUG and 17.56 m for the 2MWT over time represent a real clinical change in rehabilitation process in patients with THA. Both the 2MWT and TUG may assist in early identification of patients who may need additional rehabilitation to reduce the potential for poor outcomes after THA. Therefore, both of these tests can be used in a clinical setting with a small measurement error.