Clinically Meaningful Improvement in Rheumatoid Arthritis Assessed With RAPID-3

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Results showed that a RAPID-3 improvement of 3.8 units was clinically meaningful.
Results showed that a RAPID-3 improvement of 3.8 units was clinically meaningful.

To monitor patients with active rheumatoid arthritis (RA) in a routine care setting, the Routine Assessment of Patient Index Data 3 (RAPID-3) recognizes an improvement of 3.8 units as clinically meaningful, according to study results published in The Journal of Rheumatology.

RA is usually assessed through pooled indices based on the RA core set; however, it is not typically feasible to assess these indices through routine care, as they require formal joint counts and laboratory testing. The investigators of this study sought to establish thresholds of minimal clinically important improvement using the RAPID-3 to monitor patients with RA.   

The study included 250 adults with active RA, and changes in disease activity were measured before and after escalation of antirheumatic treatment. At baseline, participants were prescribed prednisone, a new biological therapy, or an increased dose of their current medication. Physical function, pain severity, and the patient's global assessment were measured at baseline and at follow up (1 or 4 months). The prednisone group was anticipated to respond sooner and was followed for 1 month, and the other intervention groups were followed for 4 months. At follow-up, all participants responded as to whether they judged their arthritis to be improved and rated the importance of any improvement on a 7-point scale. The RAPID-3's sensitivity to change was assessed using standardized response means, which helped determine meaningful thresholds of improvement.

Of 250 participants, 167 reported an improved arthritic status and 92% rated their improvement as at least moderately important. Participants' mean RAPID-3 score improved from 16.3 to 11.1 between baseline and follow-up. Based on conventional methods for optimizing sensitivity and specificity, the minimal clinically important improvement for RAPID-3 in patients with active RA was -3.8. Minimal clinically important improvement was slightly lower using the 0.8 specificity criterion (-3.5) and higher using the Youden index (-4.1). These estimates were consistent with the threshold of -3.6, which was considered a good RAPID-3 response. The standardized response means showed good sensitivity to change, and discrimination of improvement was similar in RAPID-3 vs other indices used for clinical trials and observational studies.

Limitations to the study included a moderate sample size and the fact that improvement was judged by the patient. Additionally, the difference in timing for follow-up visits was not analyzed. Measures of disease activity may have been influenced by existing joint damage and patient distress, and worsening of arthritic status was not estimated. Finally, the results were applicable to RA improvement only and may not be generalized to other populations.

The study investigators suggest that a RAPID-3 improvement of 3.8 units should be recognized as meaningful in routine patient care, providing clinicians with a feasible approach to documenting and monitoring a patient's RA status.

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Reference                    

Ward MM, Castrejon I, Bergman MJ, Alba MI, Guthrie LC, Pincus T. Minimal clinically important improvement of routine assessment of patient index data 3 in rheumatoid arthritis [published online October 15, 2018]. J Rheumatol. doi:10.3899/jrheum.180153

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