LUPUS ANTICOAGULANT AS A CAUSE OF PROLONGED ACTIVATED PARTIAL THROMBOPLASTIN TIME (APTT) IN PREOPERATIVE PATIENTS

Objective: This study aims at finding the prevalence of lupus anticoag ulant (LA) in a selected group of patients going for elective surgery in whom the activated partial thromboplastin time (APTT) was undertake n as part of routine preoperative coagulation screening. Recent years have witnessed enormous expansion in our knowledge of the coagulation inhibitor, especially as a cause of the prolonged (APTT). Materials an d methods: The study population consists of 900 consecutive preoperati ve patients admitted to the surgical wards at King Khalid University H ospital, Riyadh, over a period from December 1995 to March 1996. Four hundred and seventy patients were females and 430 were males; their ag es ranging from 1 to 69 years. The coagulation tests undertaken includ ed: APTT, platelet neutralization procedure (PNP), koalin clotting tim e (KCT), prothrombin time, plasma fibrinogen and clotting factors VIII , IX, and XII. Conclusion: The prevalence of LA was found to be 5.3% a mong patients as compared to 2.9% among controls (healthy blood donors n=205). Among the 48 patients who were LA positive there was signific ant reduction in the clotting factor levels (<25%), most prominent wit h FXII (15/48) and FXI (10/48). The results of this study have establi shed the fact that LA is a common cause of prolonged APTT in routine c oagulation laboratory. These results emphasize the importance of estab lishing the assay procedures for LA in major general hospitals and als o attract the attention of laboratory physicians to be on the look out for it.