Authors
Suzanne I Anjie, Sarah van Zon, Karien Bloem, Theo Rispens, Geert R D'Haens
Published in
Journal of Crohn's & colitis. Volume 20. Issue 7. Jul 07, 2026.
Abstract
Pharmacokinetic research of infliximab often relies on prospectively collected, long-term frozen serum samples. Although the effect of storage conditions on infliximab stability has been researched extensively, the influence of long-term storage on the reliability of infliximab concentration measurements remains unknown.
In this proof-of-concept study, infliximab serum concentrations measured after 2, 5, and 8 years of standardized frozen storage at -70 °C were compared with paired samples analyzed directly after collection. Equivalence was assessed using a two one-sided tests framework with predefined margins of 80%-125%, in line with FDA equivalence guidance.
Equivalence was demonstrated at all three storage durations. Geometric mean ratios were 87.0% (90% CI, 80.9%-93.6%), 103.2% (90% CI, 90.3%-117.9%), and 99.3% (90% CI, 92.5%-106.6%) at 2, 5, and 8 years, respectively, all within predefined equivalence margins. A statistically significant reduction was observed in the 2-year group (P = .010), though within equivalence bounds. No concentration-dependent bias was detected (P = .926), and Spearman correlation between fresh and frozen concentrations was high (ρ = 0.908, P < .001).
Infliximab serum concentrations remain stable after long-term frozen storage of up to 8 years under standardized conditions, supporting the validity of deferred concentration analyses in prospectively stored serum samples.
PMID:
42536070
Bibliographic data and abstract were imported from PubMed on 31 Jul 2026.
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