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4CPS-199 Comparative evaluation of enzyme-linked immunosorbent assay versus a point-of-care technique in the determination of adalimumab levels
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  1. F Cajade1,
  2. FJ Toja-Camba,
  3. L Rodríguez-Martínez2,
  4. L Arcía-Quintanilla,
  5. J Tomine3,
  6. C Feitosa2,
  7. I Zarra-Ferro1,
  8. M Barreiro-De Acosta4,
  9. J González-López1,
  10. C Mondelo-García1,
  11. A Fernández-Ferreiro1
  1. 1Hospital Universitario De Santiago De Compostela, Farmacia Hospitalaria, Santiago De Compostela, Spain
  2. 2Health Research Institute Of Santiago De Compostela Idis, Clinical Pharmacology Group, Santiago De Compostela, Spain
  3. 3Anger University, Pharmacy, Angers, France
  4. 4Hospital Universitario De Santiago De Compostela, Digestive Gastroenterology Department, Santiago De Compostela, Spain

Abstract

Background and Importance Therapeutic drug monitoring in inflammatory bowel disease (IBD) is a useful tool for optimising biologic therapy. The analysis of adalimumab (ADL) concentrations in blood through enzyme-linked immunosorbent assay (ELISA) requires accumulation of samples to make it a cost-efficient technique, delaying the results for several days. On the other hand, point-of-care (POC) tests facilitate immediate decision making by providing ADL concentration results in less than half an hour. However, it is necessary to demonstrate the equivalence of both methods and their interchangeability.

Aim and Objectives The aim of this study is to compare the reference technique for quantifying ADL levels using ELISA with quantification using POC test.

Material and Methods From our own biobank with serum samples of 200 IBD patients treated with biologics, those with adalimumab levels were selected. Later, a total of 60 patients were randomly selected: 19 for ADL sub-therapeutic range (<5 μg/ml), 21 for ADL therapeutic range (5–12 μg/ml) and 20 for ADL supra-therapeutic range (>12 μg/ml). Quantitative sandwich ELISA assay was performed with Promonitor ADL kit and POC test was performed with Quantum Blue assay. Correlation was evaluated with Spearman’s correlation coefficient (rs). Concordance between the three different therapeutic groups was assessed through weighted Cohen’s kappa (κ) and differences in classification for each group was determined using McNemar test.

Results No statistically significant differences in ADL trough levels were observed between ELISA and POC (p= 0.3101). Median values were 10 µg/mL (IQR: 3.87–13.25) for the Promonitor assay and 8.85 µg/ml (IQR: 3.67–13.62) for Quantum Blue assay. A good correlation of ADL trough levels between the two assays (rs = 0.88) and a substantial agreement in stratifying in the different groups of therapeutic ranges (K= 0.751 ± 0.063) were observed. McNemar’s test revealed no significant differences among different ranges classification (p-value=1). Bland-Altman's analysis (figure 1) was done to complete the comparison between the methods, revealing a bias difference of 0.4453.

Conclusion and Relevance The Quantum Blue POC test represents an alternative to ELISA in determining ADL concentrations, allowing results to be obtained in less time, which facilitates therapeutic decision-making in patients with IBD.

Conflict of Interest No conflict of interest.

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