Impact of exogenous antithrombin on low molecular weight heparin anti‐Xa activity assays in a pediatric and young adult leukemia and lymphoma cohort with variable antithrombin levels

Abstract

Background: Low molecular weight heparin (LMWH) remains the most commonly prescribed pediatric anticoagulant. There is debate whether LMWH anti-Xa assays with or without exogenous antithrombin (AT) best reflect anticoagulation effect, and how much discrepancy exists between assay types. Objectives: We assessed the effect of variable AT activity on LMWH anti-Xa levels in plasma samples from anticoagulated pediatric and young adult acute lymphoblastic leukemia and lymphoma (ALL/L) patients, using two instruments and their commercial kits with and without exogenous AT (ie, four platforms). Methods: We analyzed LMWH anti-Xa levels on 60 plasma samples with known AT activity from 12 enoxaparin-treated ALL/L patients, using four commercial kits from Siemens and Stago containing AT or not, on Siemens BCS and Stago STA R Max, respectively. Results: Of 236/240 samples with interpretable results, mean AT activity was 80% (46-138%). Correlation was acceptable for published kit ranges of LMWH anti-Xa levels

Interpretation of coagulation laboratory tests for patients on ECMO

“…gave the higher results compared with the Siemens Innovance ® (ATÀ/DS+) compared with the two Stago reagents Stachrom ® (AT +/DSÀ) and Liquid anti-Xa ® (ATÀ/DSÀ). 19 They conclude the addition of exogenous AT can standardise the results to the effects of reduced AT in these patients.…”

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“…14 However, although anti-Xa assays with added AT trend higher than those without, a recent paper found a good correlation between the two types of anti-Xa platforms in paediatric patients treated with low-molecular-weight heparin even when the AT activity was <70%. 15 However, while the anti-Xa level is a direct measure of heparin effect, it does not reflect the overall haemostatic status, which may depend on the amount of thrombin/AT and pro-coagulant drivers. It is an expensive test and not widely available.…”

“…14 However, although anti-Xa assays with added AT trend higher than those without, a recent paper found a good correlation between the two types of anti-Xa platforms in paediatric patients treated with low-molecular-weight heparin even when the AT activity was <70%. 15…”