Validity, reliability, responsiveness and feasibility of four hand mobility measures in hand osteoarthritis

To investigate metric properties of four hand mobility tests in hand OA patients, using the OMERACT filter.

Trained assessors examined the Hand Mobility in Scleroderma test (HAMIS), fingertip-to-palm distance (FPD), modified Kapandji index (MKI) and number of hand joints with limited mobility in participants from two cohorts [Genetics ARthrosis and Progression (n = 207) and Hand OSTeoArthritis in Secondary care (n = 174)]. Validity was appraised by assessment of correlations with other outcome measures, and ability to measure thumb vs finger mobility specifically, using cumulative probability plots. The proportion of participants changing in hand mobility based on the smallest detectable difference was calculated for responsiveness. Intraclass correlation coefficients (ICCs) for intra- and interobserver reliability, and feasibility (time to perform tests) were studied in a random sample (n = 20).

Participants displayed large variation in mobility scores. Strongest correlations were observed with structural damage (rs = 0.43-0.52) and bony swelling (rs = 0.46-0.58); correlation patterns were similar among tests. HAMIS, FPD and MKI could all measure finger mobility specifically, but only HAMIS measured thumb mobility particularly. Interobserver reliability was best for HAMIS, ICC 0.90 (95% CI: 0.76, 0.96); intraobserver reliability was excellent for all (ICCs 0.94-0.97). In 2 years, little change was observed; HAMIS was the most sensitive-to-change (smallest detectable difference 3.7% of maximum score). The mean performance time ranged from 0.7 (s.d. 0.5, for FPD) to 5.7 (s.d. 1.3, for HAMIS) min.

HAMIS, FPD, MKI and number of joints with limited mobility are all valid, reliable and feasible measures for assessing hand mobility in hand OA, although HAMIS had slightly more favourable properties. Studies assessing sensitivity-to-change in a clinical trial setting are warranted.