Reproducibility of the 6-Minute Step Test in Individuals on Hemodialysis.

BACKGROUND

Functional impairments are common in individuals with end-stage renal disease (ESRD) undergoing hemodialysis (HD); however, the clinical assessment of physical function remains challenging due to the limited availability of simple and reliable functional tests validated for this population.

PURPOSE: To evaluate the test-retest reproducibility of the 6-minute step test (6MST) in individuals undergoing HD, including the interpretation of measurement error.

METHODS

This was a cross-sectional, test retest- reliability study conducted in patients receiving maintenance HD. All assessments were performed immediately before the HD session. Participants completed the Kidney Disease Quality of Life 36-Item Short Form questionnaire (KDQOL SF-36) and performed two 6MSTs under standardized conditions. Test-retest reliability was assessed using the intraclass correlation coefficient (ICC). Absolute reliability was evaluated through the standard error of measurement (SEM) and minimal detectable change (MDC). Agreement between tests was examined using Bland-Altman analysis.

RESULTS

Fifty patients completed both test sessions. The 6MST demonstrated good test-retest reliability for total steps (ICC = 0.80), with most differences between tests remaining below the MDC95, indicating the absence of a clinically meaningful learning effect. Bland-Altman analysis showed minimal bias and acceptable limits of agreement for both total steps and heart rate measured at the sixth minute of the test. Physiological responses, including oxygen saturation, blood pressure, and perceived exertion, remained stable between sessions.

DISCUSSION: The 6 minute step test is a reliable and clinically applicable tool for assessing functional capacity in individuals undergoing hemodialysis. The absence of a relevant learning effect and the stability of physiological responses support its use for functional assessment and follow-up, even when performed before the hemodialysis session. Further studies should investigate inter-rater reproducibility and responsiveness to interventions.