Are baseline prothrombin time/partial thromboplastin time values necessary before instituting anticoagulation?

STUDY
OBJECTIVES: To determine whether baseline prothrombin time (PT) or partial thromboplastin time (PTT) values provide information that is useful to the clinician before initiating anticoagulation and whether emergency physicians elicit historical information about bleeding disorders before beginning anticoagulant therapy.
DESIGN: A three-year retrospective review of the records of 199 patients admitted through the ED with an ICD-9-CM diagnosis of deep-vein thrombosis or pulmonary embolus using a predesigned study sheet that included historical questions, baseline PT and PTT values, treatment given, timing of treatment, and underlying medical problems.
SETTING: University-affiliated tertiary-care hospital.
MEASUREMENTS AND MAIN RESULTS: Deep-vein thrombosis was the primary diagnosis in 75% of patients. Pertinent historical items were not documented in 92% to 100% of patients. Baseline PT and PTT values were obtained in 94% of patients. An elevated baseline PT was found in 26 patients, all of whom were taking warfarin. An elevated baseline PTT was found in 21 patients. These results were attributed to laboratory error (one), warfarin use (nine), heparin therapy before baseline tests (five), anticardiolipin antibodies (five, one of whom was on warfarin therapy), and unknown causes (three). Heparin therapy was not altered for any patient.
CONCLUSION: Emergency physicians rarely document pertinent questions about bleeding disorders before initiating anticoagulation therapy. Baseline PT and PTT values are almost routinely obtained despite the fact that they do not alter therapy or serve as sensitive or specific screening tests. Routine baseline PT and PTT values are rarely needed before initiating anticoagulation. Eliminating such routine testing would result in significant cost savings.