Validity and reproducibility of self-administered joint counts. A prospective longitudinal followup study in patients with rheumatoid arthritis.

OBJECTIVE To investigate the reproducibility and validity of self-administered joint counts (JC), measuring tenderness, swelling and the combination of both, in a longitudinal study. METHODS At the outpatient department a form self-administered by patients (SAI-form), was used to measure joint involvement. Concurrent joint examinations were performed by an assessor. The JC and scores for groups of joints by assessors were correlated with those by patients. As a retest the form was completed again by the patients within 10 days. Correlations between the JC measured by the test and retest were computed to investigate reproducibility. RESULTS Correlations between test and retest were high (> 0.7). Correlations between JC and groups of joints measured by the assessors and by the patients were moderate (0.06). Correlations with other disease activity variables did not differ between assessors' and patients' joint examination scores. CONCLUSION The patient-administered joint examination was reproducible; however, correlation with the assessors' joint examination was moderate. The value of the self-administered joint count needs further examination and cannot yet replace the assessor's joint examination.