Number of active joints, not diagnosis, is the primary determinant of function and performance in early synovitis

A substudy within a larger study of patients with inflammatory arthritis of less than one year, to analyze baseline measures or joint counts, laboratory values, patient questionnaires and ARA diagnostic criteria for rheumatoid arthritis, as predictors of one year performance and functional status.

229 patients with synovitis of less than one year were enrolled and evaluated at baseline and one year. Measures included the number of swollen or tender joints [active joint counts]; biological indices of inflammation [erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)]; and patient questionnaire measures of pain [Wisconsin Brief Pain Inventory], fatigue [multi-dimensional assessment of fatigue], depression [Center for Epidemiologic Studies--Depression Scale], sleep [Sleep Quality Index], performance [Human Activity Profile], and function [Sickness Impact Profile ambulation subscale and Health Assessment Questionnaire]. Correlations between these measures were evaluated using the Spearman rank order correlation. Patients were classified according to whether they met ARA criteria for RA, had high (> 7) or low (< or = 7) numbers of affected joints; and high, intermediate, or low levels of performance; and were compared using the Kruskal-Wallis test.

At baseline, an active joint count of > 7 versus < or = 7 was associated significantly with higher age, rheumatoid factor positivity, a diagnosis of rheumatoid arthritis versus spondyloarthropathy or undifferentiated arthritis, and receiving a disease modifying antirheumatic drug (DMARD), but not with sex, race, erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP), or receiving prednisone. Furthermore, high baseline active joint counts were associated significantly with patient questionnaire scores for maximum activity, fatigue and depression, but differences were not significant for sleep, ambulation and pain scores. A comparison of patients who met or did not meet criteria for RA indicated significant differences only according to the fatigue scores, but none of the other questionnaire measures. Correlations of baseline measures with one-year performance were highest for the baseline active joint count compared to laboratory and questionnaire variables. The maximum activity score at one year was predicted significantly by the baseline maximum activity score, active joint count, and age, but not by laboratory tests or whether the patient met criteria for RA.

The active joint count predicts subsequent performance and function for patients with recent onset, inflammatory synovitis more effectively than whether patients met ARA criteria for RA.