P087 Dendritic cell subsets in the maintenance of gut health and response to bioactives

Abstract

assays. Strategies to utilise drug level monitoring are yet to be subjected to randomised clinical trials. Standardisation of assays measuring biologically active compounds is hampering progress. Methods: An in house ELISA to measure drug levels of infliximab and adalimumab was established. Technical performance of the assay was established using 1. inter-assay patient samples, 2. inter assay spiked normal sera, 3. intra-assay performance across a range of drug levels, 4. sensitivity and specificity established with 63 disease control samples with positive autoantibodies (CCP, ANA, TTG, LKS or Rf) 5. Recovery of drug from spiked normal sera across the range of the standard curve 6. Doubling dilutions were used to assess linearity of the curve in patients with high levels of drug 7. Comparison to commercially available kit Results: Inter-assay co-efficient of variation 10% for IFX at 28 ug/ml, 20% for IFX 1.7 ug/ml, for ADA 9% at 6.6 ug/ml and 14% at 2.4 ug/ml. For spiked normal sera CV ranged 6 13% across concentrations 0.08 25 ug/ml for IFX and 6 26% for ADA. Intra-assay CV 2% for IFX 10 ug/ml up to 17% for IFX below 1 ug/ml, for ADA figures were 4% and 14% respectively. Specificity analysis showed mean±2SD of 0.11 ug/ml for IFX and 0.15 for ADA. Sensitivity analysis showed recovery of drug from normal sera 91 106%. Comparison with commercial ELISA kit showed expected high levels of correlation (Pearsons r = 0.9678, p < 0.0001), however Bland Altman analysis showed significant bias, with the commercial kit producing higher results.