Increased activated partial thrombin time: analysis of 250 cases discovered at laboratory

This study evaluates and discusses the potential utility (clinical value) of complementary coagulation tests performed in cases with a prolonged aPTT of no obvious etiology from a total of 85,500 routine coagulation tests carried out in our general hospital. aPTT was measured using Actin F.S.L. (Dade, plant-derived and rabbit phospholipids complex with ellagic acid as activator) and Diagen (Biotrol, rabbit phospholipids with kaolin). Tests for acquired anticoagulants and endogenous pathway factors (XII, XI, IX, VIII) were assayed if the aPTT was prolonged by 7 sec or more. 250 abnormal aPTT of previously unknown etiology were found over a 14 months period. 46% of them were without any obvious cause, and were considered "spontaneous" increases: 2/3 of these spontaneous increases were 7-9 (group A), and 1/3 were 10-19 (group B). The diagnoses found in group A were mostly deficits in the contact system, while group B contained mostly cases with acquired anticoagulants and deficits in the contact system. In group C (increases over 20"), an etiology could be established in all cases, with a predominance of acquired anticoagulants and some deficits in factors VIII and XII.