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AB0220 Myeloid-Related Proteins 8 and 14 (MRP 8/14) – Potential Biomarkers of Disease Activity of Arthritis in Children with Trisomy 21?
  1. C. Foley1,
  2. O. Killeen1,
  3. E.J. MacDermott1,
  4. D. Veale2
  1. 1Rheumatology, National Centre for Paediatric Rheumatology (NCPR), OLCHC
  2. 2St Vincent's University Hospital, Dublin, Ireland

Abstract

Background JIA is an umbrella term used to describe a heterogeneous group of diseases. To date no specific markers exist in clinical practice to predict disease activity & outcome. Down's Arthropathy (DA) was first described in the literature in 1984. There is a paucity of data with regards to the features & pathogenesis of this arthritis. MRP 8/14 are calcium-binding proteins secreted by infiltrating phagocytes in synovial inflammation. Studies have shown that their serum (Se) concentrations correlate sensitively & specifically with synovial inflammation in JIA. There is limited literature on the use of synovial fluid (SF) samples of MRP8/14 as a biomarker in JIA. To date there have been no studies looking specifically at Se or SF levels of MRP 8/14 in DA

Objectives To evaluate the use of standard (ESR and CRP) & novel (MRP 8/14) inflammatory markers as biomarkers of disease activity in DA & JIA

Methods Over a 1-year period, new cases of JIA & DA attending the NCPR had blood drawn to measure their CRP, ESR & MRP 8/14 levels. Corresponding Active Joint Count (AJC) was documented. Paired SF samples were taken for analysis from children requiring steroid JIs as treatment for their arthritis. Se & SF concentrations of MRP 8/14 were determined by sandwich ELISA. CRP & ESR were measured as part of routine clinical assessment.

Results 49 children (27 JIA, 22 DA) had Se taken for CRP, ESR & MRP 8/14 levels. 20 (18 JIA, 2 DA) had paired SF samples taken. The average AJC was 4 (1-11). 18 Se samples were taken from healthy children with T21 as a second comparison group to the DA cohort. In DA, a significant positive correlation was detected between AJC & both ESR & MRP 8/14 (SF). A similar pattern was seen in the JIA cohort, in addition SeMRP 8/14 levels positively correlated with their paired SF level. CRP did not correlate with AJC, ESR or MRP 8/14 (SF) in either group. No significant correlation was noted between Se & SF MRP 8/14 levels in DA. In fact, no significant difference between SeMRP 8/14 levels in the DA & T21 was noted.

Conclusions MRI with contrast remains the gold standard for diagnosis of synovitis. In reality, clinical assessment is the major diagnostic tool. DA is a more challenging condition than JIA in light of confounding illness & the often-associated developmental delay & non-verbal state. In DA a simple biomarker of disease would be invaluable. We have shown that CRP is a poor marker of disease activity in JIA & DA so the need for a more specific biomarker is evident. Our preliminary results suggest that children with DA (& JIA) have elevated SF levels of MRP 8/14 that correlate to disease activity. In JIA, SF concentrations of MRP 8/14 are significantly higher than their paired Se samples, however our results show significant positive correlation between the two. This suggests that SeMRP 8/14 levels are potentially accurate markers of SF levels,& in turn accurate markers of disease activity in JIA. This was not the case in our DA cohort. In fact, we found that there was no significant difference in SeMRP 8/14 levels between our DA & T21 cohort. Unlike in JIA, SeMRP 8/14 levels were not shown to be a useful biomarker of disease activity in DA. Does this suggest that DA has a different pathophysiology than JIA? Further research is required to verify our findings, & to expand our understanding of this inflammatory condition.

Disclosure of Interest None declared

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