Comparative performance of three anti-factor Xa heparin assays in patients in a medical intensive care unit receiving intravenous, unfractionated heparin.

The availability of automated anti-Xa heparin assays provides the opportunity to manage patient unfractionated heparin levels directly, rather than by the activated partial thromboplastin time. Because critically ill patients can acquire an antithrombin deficiency, we compared the performance of 3 anti-Xa heparin assays, 1 with and 2 without antithrombin supplementation, by analyzing in vitro aliquots of plasma with defined antithrombin levels and specimens from intensive care patients receiving intravenous heparin therapy. Heparin concentration recovery, in vitro, was dependent on the plasma antithrombin concentration for all 3 assays. The antithrombin-supplemented assay demonstrated improved heparin recovery in direct correlation to the heparin concentration in the plasma. The greatest effect of antithrombin supplementation occurred when the antithrombin level dropped below 40%, a level present in only 5% of the patient specimens. Analysis of patient specimens demonstrated significant correlation among the 3 assays. Classification of the clinical adequacy of patient heparin levels showed agreement of 80% or more between the antithrombin-supplemented and nonsupplemented assays. The antithrombin-supplemented assay did not significantly improve clinical usefulness.

Analytic validation and clinical evaluation of the STA LIATEST immunoturbidimetric D-dimer assay for the diagnosis of disseminated intravascular coagulation.

To evaluate the diagnostic performance of a quantitative, immunoturbidimetric D-dimer assay and compare it with other components of the proposed International Society on Thrombosis and Haemostasis disseminated intravascular coagulation (DIC) diagnostic algorithm, we retrospectively analyzed the D-dimer, platelet count, prothrombin time, and fibrinogen results for all eligible hospitalized patients (n = 241) who had a D-dimer assay ordered during a 12-month period. A receiver operating characteristic (ROC) curve constructed from the maximum D-dimer measurement for all patients was significant (P < .001) with an area under the curve (AUC) of 0.94. The ROC curves of the other tests were each significant (P < .001), but the AUCs of the prothrombin time (0.74), fibrinogen level (0.70), and platelet count (0.67) did not approach that of the D-dimer. A D-dimer cutoff of 8.2 microg/mL (8,200 microg/L) optimized sensitivity and negative predictive value for the total population and patients with a predisposing condition. Validation against 286 additional patients in a separate analysis verified the diagnostic performance of the aforementioned cutoff. A sensitive, immunoturbidimetric D-dimer assay, by itself provides excellent sensitivity and negative predictive value for the diagnosis of DIC.