Disease outcome prediction rule for arthritis validated

A prediction rule for the development of rheumatoid arthritis (RA) in patients with undifferentiated arthritis (UA) has been validated. The rule accurately estimates the risk of RA in more than 75% of patients with recent-onset UA.

van Der Helm-van Mil and associates studied 3 cohorts of patients with recent-onset UA for whom the prediction score and the corresponding chance of RA were calculated. Data on morning stiffness severity were not available in all cohorts; therefore, the prediction rule was rederived with the duration of morning stiffness as a substitute. Negative predictive values (NPVs) and positive predictive values (PPVs) were assessed, with cutoff values of 6 or lower and 8 or higher, along with the area under the receiver operating characteristic curves (AUCs) for the adjusted rule.

The AUC after application of the rederived prediction rule was 0.88, slightly lower than that from the original rule. In the 3 cohorts, the AUC was 0.83, 0.82, and 0.95; the NPV (for a prediction score of 6 or lower) was 83%, 83%, and 86%; and the PPV was 100%, 93%, and 100%.

The authors noted that the rule may be useful in daily practice for reducing undertreatment and overtreatment of patients with UA.