Comparison of Two Different Techniques to Assess Adalimumab Trough Levels in Patients with Crohn's Disease.

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Background & Aims: Loss of response to anti-tumor necrosis factor (TNF) drugs in patients with inflammatory bowel disease is likely due to low drug serum levels, and dosing anti-TNF drug concentrations may improve patients' outcome. However, there are limited data on the diagnostic accuracy and utility of currently available assays for measuring anti-TNF levels. In this study, our aim was to compare serum adalimumab concentrations with two different techniques. Methods: We assessed serum adalimumab concentrations in 23 patients with Crohn's disease during a 96-week follow-up period. Adalimumab trough levels were assessed using a sandwich principle-based enzyme-linked immunosorbent assay (ELISA) and a homogeneous mobility shift assay (HMSA). Results: At week 48, adalimumab trough levels were significantly lower in patients who experienced relapse compared to patients in remission, using both ELISA and HMSA methods: 4.8 mcg/mL (2.4-7.2 mcg/mL) vs. 7.5 mcg/mL (6.6-8.4 mcg/mL) (P=0.01) and 6.5 mcg/mL (3-10 mcg/mL) vs. 11.6 mcg/mL (7-16.2 mcg/ ml) (P=0.004), respectively. Similar results were obtained at week 96: 5.9 mcg/mL (3.3-8.5 mcg/mL) vs. 12.8 mcg/mL (9.4-16.2 mcg/mL) (P=0.001) and 4.1 mcg/mL (1.6-6.6 mcg/mL) vs. 7.5 mcg/mL (5.7-9.3 mcg/mL) (P=0.009), respectively. There was a significant correlation between ELISA and HMSA adalimumab trough levels at both 48 (r = 0.691, P=0.0003) and 96 week (r = 0.822, P=0.0001). Conclusions: ELISA and HMSA assays are accurate methods to assess adalimumab trough levels in patients with Crohn's disease and those who experience loss of response. The preferential use of one of the two techniques should be based on local availability and physicians' experience.

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