Background/Purpose:

MRP8/14 are calcium binding proteins produced by myeloid cells. Recently baseline serum levels of MRP8/14 have been shown to predict response to biologicals in rheumatoid arthritis (RA). Since methotrexate (MTX) is the first line therapy in RA we studied if MRP8/14 levels can predict response to MTX.

Methods:

Patients with RA (ACR 2010 criteria), DMARD naïve with active disease were enrolled. All patients were treated with MTX by gradually increasing dose to a maximum of 25mg/week or the maximal tolerated dose.No corticosteroids were given. Patients were followed up monthly telephonically and 2 monthly in the clinic. At 4 months disease activity was measured by DAS 28 and EULAR response was assessed.All patients who needed rescue therapy after 2 months or did not respond at 4 months were classified as non-responders.

Results:

90 patients were enrolled in the study, of which 3 were excluded(discontinued MTX within 4-6 weeks due to toxicity). Thus 87 patients (74 females) with mean age 40.8±12.1yr, mean duration of disease 28±25.5months and mean DAS28 4.5±0.7) were analyzed. The mean serum MRP 8/14 level at baseline was 27.612±21.353µg/ml.The serum MRP8/14 had good correlation with DAS28CRP (r = 0.35; p=0.001).The MRP8/14 levels fell significantly after 4 months of treatment (12.734 ± 9.966µg/ml; p<0.001).

Among 87 patients 69 were classified as responders (good 43, moderate 26) while 18 were non- responders. The mean baseline level of MRP 8/14 was higher among responders as compared to non- responders (29.280 ± 20.411µg/ml  vs 19.152 ± 23.341µg/ml; p=0.002). Comparing the fall in responders and non-responders separately,  the levels reduced significantly only in the responders(29.280 ± 20.411 µg/ml to 12.487± 9.987 µg/ml; p<0.001), but not in the non-responders(19.152 ± 23.341µg/ml to 15.173±10.189 µg/ml; p=0.687).Receiver-operation characteristic (ROC) analysis showed that MRP8/14 was a good predictor of response with an area under curve(AUC)of 0.719 better than that of DAS28CRP(AUC-0.635) and DAS28ESR (AUC-0.489).

Conclusion:

MRP8/14 is a good biomarker of disease activity in RA and higher levels predict response to MTX.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/serum-myeloid-related-protein-814-levels-in-rheumatoid-arthritis-marker-of-disease-activity-and-response-to-methotrexate-in-dmard-naive-patients/