Lack of anti-factor Xa assay standardization results in significant low molecular weight heparin (enoxaparin) dose variation in neonates and children

Abstract

Introduction: Enoxaparin is a frequently used anticoagulant in children. Unlike in adults, consensus guidelines recommend therapeutic monitoring to a target anti-factor Xa level of 0.5-1 U mL-1. Therapeutic ranges are not well correlated with clinical outcomes (e.g. thrombosis or hemorrhage), and assays are not standardized. Owing to limited reagent supplies, our clinical laboratory conducted a validation process and switched anti-FXa assays. Although the assays correlated well with each other, anti-FXa values were, on average, 33% higher with the new assay. The target anti-FXa range was not altered. We evaluated how this change in anti-FXa assays influenced enoxaparin dosing (mg kg-1). Meth..