Monitoring of heparin therapy: Should heparin assays also reflect the patient's antithrombin concentration?

Low‐molecular‐weight heparin in patients with advanced cirrhosis

“…This was in accordance with a previous study by Hahn and colleagues, who found that in patients with AT deficiency, the actual heparin concentration was higher than the results of the activity assay suggested. Thus, the authors concluded that AT assessment is mandatory in specific patient populations (30). Similarly, in a paediatric population, Ignjatovic et al (31) found substantially different results between three commonly used methods for anti-Xa activity assessment.…”

Routine coagulation assays underestimate levels of antithrombin‐dependent drugs but not of direct anticoagulant drugs in plasma from patients with cirrhosis

“…Indeed, when exogenous AT was added to the anti-Xa assay, the reduced recovery of the LMWH in patients compared to controls was fully blunted. Furthermore, other studies have also shown decreased anti-Xa values in patients with AT deficiency treated with UFH or LMWH (Holm et al, 1987;Kuhle et al, 2006;Lehman et al, 2006). In addition, in neonates, who have reduced plasma levels of AT, the anti-Xa assays have also been shown to be unreliable for this reason (Schmidt et al, 1988).…”

Problems In Laboratory Monitoring Of Heparin Dosage

“…Some anti-Xa-assay techniques involve addition of exogenous anti-thrombin to the plasma, whereas some consider this to be artificial and that results may be less relevant as they do not reflect the anticoagulant effect in vivo, which is mediated through plasma anti-thrombin (Bartle et al, 1980;Holm et al, 1987). This is of importance as heparin therapy usually produces a decrease in circulating anti-thrombin that is independent of the initial dose, is detectable after 1 d, peaks at approximately 30% after 2±4 d and returns to normal 2±3 d after cessation of therapy (Marciniak & Gockerman, 1977;Holm et al, 1985).…”