Effect of analytic uncertainty of conventional and point-of-care assays of activated partial thromboplastin time on clinical decisions in heparin therapy.

The authors assessed the capability of assays of activated partial thromboplastin time (aPTT) for supporting clinical decision algorithms for heparin therapies of varying complexity. Blood samples were collected prospectively in three explicit management strategies from 100 sequential patients for whom heparin dosage was adjusted for therapeutic monitoring, femoral venous sheath removal after cardiac catheterization, or heparinization after thrombolytic therapy. In two- and three-way decision algorithms, conventional and point-of-care aPTT assays agreed with heparin assays in approximately two thirds of cases, and the two aPTT assays agreed in 80% or more of all cases. In six-way decision algorithms, the two aPTT assays agreed in only about half of all cases. The authors conclude that the reliability of point-of-care aPTT assays is similar to that of conventional assays. Both techniques can support two- and three-way decision algorithms but not some more complex patient classifications.