Serum cartilage oligomeric matrix protein (COMP) following infliximab treatment in patients with rheumatoid arthritis: Analitical performances and clinical correlations

Background. Cartilage oligomeric matrix protein (COMP) is a biomarker for the cartilage turnover and is described as a valuable parameter for the assessment of therapy response in patients with rheumatoid arthritis (RA). This study evaluated the analytical performances and clinical correlations of an automated enzyme immunoassay for the detection of COMP (COMP R ELISA; AnaMar Medical AB, Lund, Sweden). Methods. Commercial controls and serum pool were used to evaluation of method precision and accuracy in accordance with the description in the NCCLS guideline EP15-A2. Twenty-eight patients with established RA were studied during a 6-month period from initiation of treatment with infliximab. COMP levels were correlated with clinical evaluation and laboratory tests (VES, C reactive protein) and compared before and after treatment. Results. The total imprecision (CV% within-laboratory) was 3.27%-5.50% for concentrations ranging between 7.09 and 14.69 U/L. The test was linear for concentrations ranging between 4 and 32 U/L. COMP levels decreased in ACR responders patients, remained unchanged or increased in ACR non responders. There was no significant correlation between COMP levels and laboratory test evaluated. Conclusions. The COMP assay we examined on a fully automated system showed a good analytical performances (precision and linearity) and can provide useful data for evaluating tissue effects of novel treatment in RA

Riboflavin responsive mitochondrial myopathy is a new phenotype of dihydrolipoamide dehydrogenase deficiency. The chaperon-like effect of vitamin B2.

Dihydrolipoamide dehydrogenase (DLD, E3) is a flavoprotein common to pyruvate, α-ketoglutarate and branched-chain α-keto acid dehydrogenases. We found two novel DLD mutations (p.I40Lfs*4; p.G461E) in a 19year-old patient with lactic acidosis and a complex amino- and organic aciduria consistent with DLD deficiency, manifesting progressive exertional fatigue. Muscle biopsy showed mitochondrial proliferation and lack of DLD cross-reacting material. Riboflavin supplementation determined the complete resolution of exercise intolerance with the partial restoration of the DLD protein and disappearance of mitochondrial proliferation in the muscle. Morphological and functional studies support the riboflavin chaperon-like role in stabilizing DLD protein with rescue of its expression in the muscle