A rapid screen for lupus anticoagulant with good discrimination from oral anticoagulants, congenital factor deficiency and heparin, is provided by comparing a sensitive and an insensitive APTT reagent

Abstract

Lupus anticoagulants (LA) are associated with an increased risk of thrombosis and laboratory detection is of major importance. Various tests are available for LA screening and confirmation, but they differ in sensitivity and specificity, frequently lacking the ability to discriminate between the presence of LA, heparin and oral anticoagulants. We noticed that a patient with LA who had a prolonged activated partial thromboplastin time (APTT) by our routine method, gave a normal result with a different APTT reagent. This latter reagent, which contained soy bean phosphatides (SBP), was compared with a reagent containing rabbit brain phospholipids complexed with kaolin (RBK), for APTT measurement in a variety of patients. There was no significant difference in APTT ratio between the two reagents in plasma samples from healthy normal subjects. In LA samples, SBP gave consistently lower APTT ratios than RBK (mean × SEM, 1.04 × 0.05 and 2.08 × 0.19 for SBP and RBK respectively; PP