Concurrent validity and measurement error of stair climb test in people with pre-radiographic to mild knee osteoarthritis

Abstract

BackgroundStair climbing is the task first affected in patients with knee osteoarthritis (OA); therefore, the precise measurement of time required to climb stairs is important to identify mobility limitations, particularly in the early phase of knee OA. Research questionThis study aimed to examine the test-retest reliability, measurement error, and concurrent validity of the stopwatch-based stair-climb test (SCT) in adults with pre-radiographic to mild knee OA. MethodsFifty-nine participants (mean age, 59.1 [range, 50–69] years; 72.9% female) with Kellgren and Lawrence grade ≤2 disease underwent an 11-step SCT (11-SCT) in accordance with the Osteoarthritis Research Society International recommended method while wearing pressure sensor-mounted standard shoes that is used as a gold standard procedure. Test-retest reliability, measurement errors, and the concurrent validity of the stopwatch-based 11-SCT were evaluated. ResultsThe test-retest reliability of the stopwatch-based 11-SCT was excellent (intra-class correlation coefficient1,1 [ICC1,1], 0.952; 95% confidence interval [CI], 0.560 to 0.985; p < 0.001) and the minimal detectable change95 was 0.102 s. Concurrent validity was excellent (ICC2,1: 0.957; 95% CI: 0.661 to 0.986; p < 0.001). SignificanceThe stopwatch-based 11-SCT had high test-retest reliability and high concurrent validity, which justify its clinical use for identifying mobility limitations in individuals with pre-radiographic to mild knee OA. A difference of 0.2 s in the stopwatch-based 11-SCT time would be considered a true difference beyond a 95% measurement error.