Test-Retest Reliability for Physical Function Measures in Patients with Chronic Kidney Disease.

Abstract

It is important to determine relative and absolute reliability values in outcome measures that are used in clinical practice so as to discriminate between true changes following exercise interventions for patients with chronic kidney disease (CKD). The study aimed to assess test-retest reliability of the incremental shuttle walk test (ISWT), sit-to-stand transfers in 60 seconds (STS-60), timed up and go (TUAG), Duke's activity status index (DASI) and hospital anxiety and depression scale (HAD) in patients with CKD. This study was a pragmatic non-randomised controlled trial. Forty people attended two study visits within a 16-day window involving the ISWT, STS-60, TUAG, DASI and HAD tests. Relative reliability was assessed using intraclass correlation coefficient (ICC) and absolute reliability using the standard error of measurement (SEM) and minimal detectable change (MDC). Good test-retest reliability was found for the entire sample size across all outcome measures, with TUAG having the highest (ICC = 0.96) and HAD the lowest (ICC = 0.71). The MDC scores at 90% confidence interval (CI) were: 79.6 m for the ISWT, 2.9 seconds for the TUAG, 7.0 repetitions for the STS-60, 8.4 for the DASI, 3.8 for the anxiety HAD subscale and 4.4 for the depression HAD subscale. This study demonstrated good test-retest reliability for all outcome measures across the CKD trajectory but caution needs to be taken when interpreting the findings for each CKD sub-group separately. The MDC scores at 90% CI can support therapists in determining a true improvement in CKD patients' physical or mental performance.