To study the characteristics of the Multidimensional Health Assessment Questionnaire (MDHAQ) in Finnish patients with rheumatoid arthritis.
The reliability of the questionnaire was tested by test-retest procedure. Construct validity was studied by factor analysis and convergent validity by calculating correlations between the Finnish MDHAQ (Finn-MDHAQ) scales and the Finnish Health Assessment Questionnaire (HAQ) and the Finnish Arthritis Impact Measurement Scales (Finn-AIMS2). Correlations between Finn-MDHAQ and measures of clinical characteristics, disease activity, and functional class were also measured. An item analysis was made of the Finn-MDHAQ scales Function (FN) and Psychological (PS).
Internal consistency on the FN scale was 0.92 (95% lower limit 0.89) and 0.66 (0.56) on the PS scale. Reproducibility (95% CI) on FN was 0.93 (0.82 to 0.97) and on PS 0.84 (0.70 to 0.92). Factor analysis identified 2 factors, mobility of upper extremities and trunk, and mobility of lower extremities. Strong correlations were found between the FN scale and HAQ and physical subscales of Finn-AIMS2 and between PS and the psychological subscales of Finn-AIMS2. In item analysis corrected item correlation was high on the Finn-MDHAQ scales, except in one item on the PS scale.
The Finn-MDHAQ is an applicable, reliable, and valid instrument for the part of the FN scale measuring functional ability in Finnish rheumatic patients. The incongruity in the PS scale structure that produced moderate internal consistency can be overcome with minor modifications.