An improvement of nearly 4 points on a 30-point, patient-scored disease severity index appears to be clinically meaningful for adults with active RA, according to a recent clinical trial analysis.
Richard Clark, NIAMS
Dr. Michael M. Ward
A 3.8-point decrease represented the minimal clinically important improvement in the Routine Assessment of Patient Index Data 3 (RAPID-3) index, investigators reported in The Journal of Rheumatology.
“Clinicians may feel comfortable documenting and monitoring patient status, recognizing an improvement of 3.8 units in patients with active RA to be meaningful in routine patient care,” Michael M. Ward, MD, PhD, of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and his coinvestigators wrote.
The RAPID-3 index consists of three patient self-report measures out of the seven-item RA Core Data Set: physical function, pain, and patient’s global assessment. The index was initially designed to be feasible in routine care, such that a patient could fill it out in the waiting area, Dr. Ward and his colleagues noted in their report.
Previous investigations have shown that RAPID-3 is highly correlated with the 28-joint count Disease Activity Score (DAS28) and the Clinical Disease Activity Index, and in one study, it was more likely than erythrocyte sedimentation rate (ESR) to identify incomplete responses to methotrexate.
However, prior to the present study, there were no reported estimates of the minimal clinically important improvement for the RAPID-3 index.
Knowing whether or not a decrease in RAPID-3 is clinically meaningful to patients would help clinicians interpret those changes in response to treatment, Dr. Ward and his coauthors wrote.
In the current study, RAPID-3 was calculated before and after escalation of treatment in a prospective study involving 250 adults with active RA, including 195 women (78%). The mean age of the patients was 51 years, and the median duration of RA was more than 6 years.
At the patients’ baseline visit and evaluation, rheumatologists prescribed prednisone, a new disease-modifying treatment, a new biologic, or increased the dose of a current treatment. The follow-up visit occurred at 4 months for most patients, though follow-up was at 1 month for prednisone-treated patients because of an expected rapid response.
At baseline, the mean RAPID-3 score was 16.3, which improved to 11.1 at the follow-up visit, for a mean change of –5.2 points, according to the investigators. The standardized response mean was –0.79 (95% confidence interval, –0.71 to –0.88), which investigators said demonstrated good sensitivity to change.
They found that the minimal clinically important improvement was –3.8 in a statistical analysis that optimized sensitivity and specificity, and –3.5 and –4.1 by alternate statistical criteria.
However, Dr. Ward and his coauthors cautioned that these estimates should be applied only to patient groups that have high levels of RA activity, similar to this study, in which patients had a baseline mean DAS28-ESR of 6.16 and a mean Simplified Disease Activity Index of 38.6.
Patients with low RA activity are closer to an acceptable symptom state, making the minimal clinically important improvement less relevant. “The margin for symptom improvement becomes smaller and ultimately indiscernible as the level of activity decreases,” they explained in their report.
The study was supported in part through the NIAMS Intramural Research Program and a grant from the U.S. Public Health Service. No conflicts of interest were reported.
SOURCE: Ward MM et al. J Rheumatol. 2018 Oct 15. doi: 10.3899/jrheum.180153.