Handheld Dynamometry Testing During Dialysis: Intrarater and Interrater Reliability Study

Objectives The aim was to assess the intrarater and interrater reliability of the handheld dynamometry testing of lower limb muscles during hemodialysis. Methods This is a cross-sectional study including subjects undertaking hemodialysis for at least 3 months. Handheld dynamometer measurements of hip and ankle muscle strength (N) were registered on 4 different occasions, 2 trials by raters A and 2 by raters B, to evaluate the intrarater and interrater reliability. Bland-Altman plots were constructed to examine the agreement between raters by scoring the difference between raters against the mean of both raters' scores. The intraclass correlation coefficient was used to assess relative intrarater and interrater reliability. Absolute reliability was assessed with the minimal detectable change. Results Fifty-six participants (median age, 67 years) data showed high to very high relative reliability (intraclass correlation coefficients 0.75-0.98). Regarding the intrarater absolute reliability, minimal detectable change score 90% confidence interval values ranged from 27.0 to 41.6.5 N (0.14-0.26 N/kg m 2 ) for hip muscles but increased for ankle muscles. Interrater values were wider. The mean difference between trials ranged narrowly across the two-time points for raters A (1.0-19.3 N) and for raters B (1.3 - 11.4 N). The mean difference between raters ranged from 2.4 to 13.5 N. The Bland-Altman plot revealed a systematic bias for raters A in ankle plantar flexion. Conclusions The assessment of the hip flexion and abduction strength during dialysis with a handheld dynamometer is reliable and safe. Normalized data provides more reliable results.