Activated partial thromboplastin time for automated techniques: a comparison of two commonly used reagents.

In a comparison between two widely used activated partial thromboplastin time reagents (Instrumentation Laboratories, Manchester low-opacity), using one popular instrument (Automated Coagulation Laboratory, model 300R), a wide range of defects and 40 normals were tested. There was generally good agreement between methods, although for samples from patients on high heparin dosages the agreement was poor. The manufacturer's recommendation for the therapeutic range for heparin for the Instrumentation Laboratory reagent was lower than the range in current general use. The Manchester reagent was more sensitive to the lupus anticoagulant.