Changes in the Multi-Biomarker Disease Activity (MBDA) score ≥8 correspond with a clinically meaningful change in rheumatoid arthritis (RA) disease activity, which can used as a benchmark for therapeutic drug efficacy, according to study results published in Clinical Rheumatology.

The study included participants with seropositive RA, clinically stable disease, and no changes in RA medications for 4 weeks prior to the study (n=28). The researchers collected 9 serum samples over 4 consecutive days. They assessed variability of the MBDA score, a validated RA disease activity measure based on 12 serum biomarkers, on a daily and diurnal basis.

The researchers calculated the standard deviation (SD) of MBDA scores using a linear mixed model including random effects for patient, day, and time of day. The researchers calculated the minimally important difference (MID) and performed a subgroup analysis in participants with active RA.

The researchers found that the SD of MBDA score change in all participants was 4.7 in a combined daily-diurnal variation analysis, which gave them an MID of 11. For the subset of participants with active RA, the researchers found an SD of 3.6, corresponding to an MID of 8.

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“The knowledge of diurnal and daily variation of the MBDA score and defined MID should be helpful to the practicing rheumatologist in their decision-making and patient care when using MBDA test,” the researchers wrote.

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Reference

Chernoff D, Eastman PS, Hwang CC, et al. Determination of the minimally importance difference (MID) in multi-biomarker disease activity (MBDA) test scores: impact of diurnal and daily biomarker variation patterns on MBDA scores [published online August 29, 2018]. Clin Rheumatol. doi:10.1007/s10067-018-4276-y