title: Partial thromboplastin time: prediction of adverse events and poor prognosis by low abnormal values.
abstract: BACKGROUND
  Clinical observations suggest an increased incidence of bleeding and thrombosis in association with a shortened partial thromboplastin time (PTT).
  
  
  OBJECTIVE
  To determine whether abnormally fast PTTs are associated with an increased risk of death, thromboses, bleeding, and the overall occurrence of morbid events.
  
  
  METHODS
  The medical records of 199 patients admitted in a 1-year period to a Veterans Affairs medical center were reviewed for PTTs and the events of death, thromboses, and severe bleeding. Group 0 (n = 49) consisted of patients with abnormally fast PTTs (<23 seconds). Group 1 (n = 50) consisted of patients with fast normal PTTs (23-25 seconds), and the control group, group 2 (n = 100), contained patients with PTTs from 28 to 31 seconds. The Cox proportional hazards regression was used to analyze the time-independent covariates of PTT groups, surgery, cancer, and other clinical variables as predictors of 3 outcome variables: bleeding, thrombosis, and death.
  
  
  RESULTS
  Of the covariates examined, the PTT was found to be the most significant predictor of poor outcome. A statistically significant association was found between the PTT and time to death (P<.001), thrombotic events (P<.001), and bleeding (P<.006), and between the PTT and overall occurrence of morbid events (P<.001). Furthermore, survival curves showed that the greatest hazards of death, thrombosis, bleeding, and overall morbidity consistently occurred in group 0 compared with groups 1 and 2.
  
  
  CONCLUSIONS
  Abnormally fast PTTs, particularly if confirmed on repeated testing, indicate a significant risk of subsequent death, thrombosis, bleeding, and overall morbidity. Careful examination of patients with low PTTs may reduce such associated morbidity and mortality.
authors.affiliation: Department of Medicine, University of Nevada School of Medicine, Reno 89520, USA.
authors.forename: N M
authors.initials: NM
authors.lastname: Reddy
authors.forename: S W
authors.initials: SW
authors.lastname: Hall
authors.forename: F R
authors.initials: FR
authors.lastname: MacKintosh
mesh_terms: D016022:Case-Control Studies; D006470:Hemorrhage / Q000097:blood / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008297:Male; D009017:Morbidity; D010314:Partial Thromboplastin Time; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012307:Risk Factors; D016019:Survival Analysis; D013927:Thrombosis / Q000097:blood / Q000453:epidemiology*