COMPARATIVE-EVALUATION OF A GERMAN VERSIO N OF THE HEALTH ASSESSMENT QUESTIONNAIRE (HAQ) AND THE HANNOVER FUNCTIONAL ABILITY QUESTIONNAIRE (HFAQ)

Objective: To translate the Health Assessment Questionnaire Disability Index (HAQ) into a German version, to validate and to compare its pro perties with two different versions of the Hannover Functional Ability Questionnaire (HFAQ) in a German speaking population. Methods: The te st-retest reliability was tested by Pearson correlation in 32 outpatie nts of the Department of Rheumatology of the Medizinische Hochschule H annover. For retesting, the questionnaire was mailed to them 1 week la ter. To validate the questionnaire it was administered to 110 inpatien ts in three different hospitals. All patients fulfilled the American C ollege of Rheumatology 1987 revised criteria of rheumatoid arthritis ( RA) or the Rome criteria of definitive inactive RA. The internal consi stency was measured by Cronbach's coefficient alpha (CCA). To assess c riterion validity we compared the HAQ and the two versions of the HFAQ with Keitel's test (KT) and the modified Steinbrocker classification (mSC). Construct validity was assessed by comparing these instruments with different clinical and laboratory variables. A multivariate analy sis was used to identify the most important factors that are influenci ng the HAQ- and HFAQ-scores. Results. Test-retest reliability of the H AQ was r=0.94. CCA was 0.91 (HAQ), 0.90 (HFAQ-P) and 0.93 (HFAQ-PR). T he KT Pearson correlation coefficients reached r=-0.73 (HAQ), r=+0.74 (HFAQ-P) and r=+0.71 (HFAQ-PR). The mSC correlated r=+0.75 (HAQ), r=-0 .72 (HFAQ-P) and r=-0.70 (HFAQ-PR). The correlation coefficients of HA Q/HFAQ-P was r=-0.87 and of HAQ/HFAQ-PR r=-0.88. The correlations betw een other clinical and laboratory variables reached from r=+/-0,58 (pa in/HAQ) to r=+/-0,11 (number of swollen joints/HFAQ-R). In backward mu ltiple regression analysis 59-64% of the variance of disability measur ed by the questionnaires was explained predominantly by pain (32-33%) and by range of motion (16-21%). Conclusion: The German version of the HAQ presented here and the two versions of the HFAQ are reliable and valid instruments for measuring functional disability in a German-spea king population with RA. The construct measured by the HAQ and both ve rsions of the HFAQ showed a high degree of correspondence.