Measuring health status in psoriatic arthritis: the Health Assessment Questionnaire and its modification

The Health Assessment Questionnaire (HAQ) has proven to be a reliable and valid measure of outcome for a variety of arthritides. A recent modification of HAQ for spondyloarthropathy (HAQ-S) has also been reported. Our purpose was to evaluate the HAQ and HAQ-S as outcome measures in the assessment of patients with psoriatic arthritis (PsA).

The HAQ, including HAQ-S was administered to all patients attending our Psoriatic Arthritis Clinic between June and December, 1993. Clinical and radiological assessments were performed according to a standard protocol that measures disease activity, fibrositic tender points (TP), disease severity and damage. Analysis was performed using SAS for the PC.

The patient population included 114 patients, 70 men and 44 women with a mean age of 49.3 years and a mean arthritis duration of 15.1 years. The mean HAQ score was 0.50, while the mean HAQ-S score was 0.53 (scores range 0 to 3 for this instrument). The overall HAQ and HAQ-S disability scores were highly correlated with several clinical measures of function, including grip strength (r = -0.63 and -0.59, respectively). American College of Rheumatology functional class (r = 0.59 and 0.60, respectively), as well as the number of fibrositic TP (r = 0.54 and 0.57, respectively). These disability scores also correlated highly with the overall number of actively inflamed joints (r = 0.49 and 0.50, respectively); however, they correlated only moderately or poorly with other measures of disease activity such as morning stiffness, total number of joint effusions, erythrocyte sedimentation rate (ESR) and the PASI score for psoriasis and with all measures of disease severity. A similar pattern of correlations was found between the individual subscales of the HAQ and HAQ-S and the clinical measures of function, activity, and severity, as well as between the pain scale and the various clinical measures. However, the correlations are generally lower.

Our data suggest that HAQ and HAQ-S capture clinical measures of function and pain in PsA but do not correlate with disease severity. The HAQ and its modification for spondyloarthropathy may reflect fibromyaglia as a measure of pain and tenderness in these patients. Thus, the clinical assessment of disease activity and both clinical and radiological assessments of joint damage remain important outcome measures in PsA.