Ab1444 biomarkers in juvenile idiopatic arthritis: description of groups with different degrees of discrepancy between serum calprotectin and c-reactive protein.

Background There are no specific biomarkers of disease activity in for Juvenile Idiopathic Arthritis (JIA), and therefore it is important to identify new molecules which help us in daily practice to offer individualized treatment options. Serum Calprotectin (CLP) is an emerging biomarker of inflammation. Recent studies [1] suggest that disease activity correlates better with CLP than with classic acute phase reactants such as C-reactive Protein (CRP). Objectives To determine the clinical characteristics of paediatric patients with Juvenile Idiopathic Arthritis (JIA) who have discrepancy between Serum Calprotectin and C-reactive Protein. Methods An analytical transversal study was performed including patients with JIA from a paediatric rheumatology clinic between 2017 and 2021. A total of 25 patients were included, who had at least one measurement of CLP in daily practice. Demographic, analytical and clinical data were collected. The JADAS score by physical examination and ultrasound was collected in patients with peripheral arthritis. Results A total of 25 patients were included, 48% were female and the mean age was 11.5 (±4.6) years. A total of 11 (44%) patients had discrepancy between CLP and CRP. Among them, 9 (81.8%) had elevated CLP and low CRP, whereas only 2 (18.2%) had low CLP with elevated CRP. At the time of performing the analysis, 44% of the patients had an active disease. The oligoarticular JIA subtype was the one that presented a larger patient’s percentage (54.5%) with discrepancy and elevated CLP. The details of clinical and analytical characteristics of the patients are shown in Table 1. No discrepancy. Low (n=11) Discrepancy. Low CLP (n=2) Discrepancy. High CLP (n=9) No discrepancy. High (n=3) Age (years), mean (SD) 12.2 (±4.6) 8.0 (±11.1) 10.3 (±3.5) 14.4 (±3.0) JIA subtypes, n (%) - ERA + juvenile EA + APs 5 (45.4) 0 (0) 2 (22.2) 0 (0) - Oligoarticular 3 (27.3) 1 (50) 5 (55.6 ) 2 (66.7) - Polyarticular 2 (18.2) 1 (50) 1 (11.1) 1 (33.3) - Systemic 1 (9.1) 0 (0) 1 (11.1) 0 (0) Biomarkers, median (IQR) - CRP (mg/L) 0.5 (0.6) 8.2 (5) 1.7 (2.1) 6.3 (11.8) - ESR (mm/h) 5 (8) 28 (32) 13 (12) 21 (56) - Calprotectin (µg/mL) 1.4 (0.8) 0.9 (1.6) 4.3 (1.7) 4 (2.3) JIA activity according to clinical criteria, n (%) - Active 4 (36.3) 2 (100) 3 (33.3 ) 2 (66.7) - Inactive 7 (63.6) 0 (0) 6 (66.7) 1 (33.3) JIA activity according to JADAS, n (%) - JADAS: activity 0 (0) 2 (100) 2 (22.2) 1 (33.3) - JADAS US: activity 0 (0) 2 (100) 1 (11.1) 1 (33.3) Uveitis , n (%) - Acute uveitis 0 (0) 0 (0) 1 (11.1) 0 (0) Treatment , n (%) - PDN 2 (18.2) 1 (50) 1 (11.1) 1 (33.3) - DMARD 6 (54.5) 1 (50) 3 (33.3) 3 (100) - bDMARD 3 (27.3) 0 (0) 2 (22.2) 1 (33.3) In the subgroup of patients with discrepancy and elevated CLP there were 3 (33.3%) with an active disease. Among them, 66.7% were female and all of them had an oligoarticular JIA. One of them was in a flare with both an active arthritis and uveitis at the moment of the analysis. None of them were under treatment with prednisone nor DMARD (disease-modifying antirheumatic drugs). Conclusion There was discrepancy between CLP and CRP in 44% of the sample. Among them, most (81.8%) had high CLP without elevation of CRP. The JIA subtype that presented discrepancy with elevated CLP was the oligoarticular one. A total of 3 (33%) patients were active in the group with discrepancy and elevated CLP, one of them being in a flare with both an active arthritis and uveitis. Reference [1] La C, Lê PQ, Ferster A, Goffin L, Spruyt D, Lauwerys B, et al. Serum calprotectin (S100A8/A9): a promising biomarker in diagnosis and follow-up in different subgroups of juvenile idiopathic arthritis. RMD Open [Internet] 2021 [consultado 10 de abril de 2022]; 7 (2): e001646. Disponible en: https://rmdopen.bmj.com/content/rmdopen/7/2/e001646.full.pdf Acknowledgements: NIL. Disclosure of Interests None Declared.