title: Causes of isolated prolonged activated partial thromboplastin time in an acute care general hospital.
abstract: BACKGROUND
  To determine the causes of isolated prolonged activated partial thromboplastin time (APTT) in an acute care general hospital setting so as to rationalise fresh frozen plasma usage.
  
  
  METHODS
  A prospective study of consecutive patients with isolated prolonged APTT presenting to our hospital between February 2002 and January 2004 was performed. All patients had normal prothrombin time and thrombin time. For all patients, an initial 50:50 correction with plasma was done and a standard panel of tests was performed. These included detection of lupus anticoagulant using two different sensitive tests; measurement of coagulant factors VIII (FVIII), IX, XI and XII, which are involved in the intrinsic arm of haemostasis; von Willebrand factor antigen (vWF:Ag) levels and for those with FVIII levels less than 10 percent, an inhibitor assay using the Nijmegen modification of the Bethesda method.
  
  
  RESULTS
  177 patients were included in the study. The cohort was typical of an acute care general hospital patient population in Singapore in terms of age, sex and racial distribution. The most common cause of an isolated prolonged APTT in our study was the presence of lupus anticoagulant (53.1 percent of cases). In 31.6 percent of cases, obvious cause could be detected after our panel of tests. These patients mostly had mildly prolonged APTT that could be both correctable and non-correctable by normal plasma. Prolonged APTT due to factor deficiency was relatively rare with those that may potentially cause haemorrhagic problems only accounting for 4.5 percent of cases.
  
  
  CONCLUSIONS
  Our study suggests that most of the causes of isolated prolonged APTT do not lead to haemorrhagic complications. In fact, in a majority, it may signify an underlying thrombophilic condition. As a result, prolongation of APTT should be fully investigated and correction with fresh frozen plasma should be used only when appropriate.
authors.affiliation: Department of Pathology and Laboratory Medicine, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore 380433. chngwj@nuh.com.sg
authors.forename: W J
authors.initials: WJ
authors.lastname: Chng
authors.forename: C
authors.initials: C
authors.lastname: Sum
authors.forename: P
authors.initials: P
authors.lastname: Kuperan
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001778:Blood Coagulation Disorders / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D006474:Hemorrhagic Disorders / Q000209:etiology* / Q000503:physiopathology; D006769:Hospitals, General; D006801:Humans; D016682:Lupus Coagulation Inhibitor; D008297:Male; D008875:Middle Aged; D010314:Partial Thromboplastin Time; D010949:Plasma; D011446:Prospective Studies; D011517:Prothrombin Time; D018570:Risk Assessment; D012307:Risk Factors; D012846:Singapore; D013997:Time Factors
chemical_list: D016682:Lupus Coagulation Inhibitor