VALIDATION DATA

The Map-Hand showed a high Person Separation Index reliability (PSI), even after adjustment for local dependency (PSI range: 0.95–0.92). Reliability measured by Cronbach Alpha (α) was also excellent (α = 0.96). In another research by Fernandes et al, Cronbach’s α of 0.86 was determined in a cohort of patients with OA.

Test-retest reliability was based on 35 patients (70%) who reported their hand function as stable in the test period. The mean difference between the 2 scorings was 0.032 (SD 0.171), and the ICC coefficient for re-scoring was 0.94 (95% CI 0.89, 0.97).

The SEM was 1.44 and the MDC95 score was 3.99. There was no floor or ceiling effects present.

To ensure that the items were relevant for patients with RA, semi-structured interviews were conducted with 60 patients from the inpatient and outpatient clinics of the rheumatology department at Diakonhjemmet Hospital in Oslo. In addition, items were matched to the eight main handgrips using the Sollerman handgrip classification 

Face and content validity were assessed by analysing videotapes of handgrips used by 3 persons with different level of functional ability (1 healthy hospital staff member, 1 patient with moderate functional limitations and 1 patient with severe limitations) when performing the activities included in the initial MAP-Hand item pool.

The MAP-Hand questionnaire also showed an overall fit to the Rasch model in people with carpometacarpal joint osteoarthritis.

Most of the initial 31 items had good face and content validity. Following Rasch analysis the measure was reduced to 18 items, which had good evidence for unidimensionality, a broad range of item difficulty, good person separation and ordered thresholds in a 4-point scale.

MAP-HAND correlated strongly with HAQ20 (rs = .88), ULHAQ (rs = .91), SF-36v2 (PF) Score (rs = −.80) and DASH (rs = .93), indicating strong concurrent validity.