Overuse of prothrombin and partial thromboplastin coagulation tests in medical inpatients.

INTRODUCTION: In the monitoring of anticoagulant therapy, prothrombin time (PT) is used to measure the effect of warfarin, whereas the partial thromboplastin time (PTT) measures the therapeutic effect of unfractionated heparin. Low molecular weight heparin (LMWH) does not require routine monitoring.
OBJECTIVE: We collected data on the frequency of simultaneous PT and PTT requests, where only one or neither is indicated, and estimated the potential cost savings if ordering was appropriate.
METHODS: The study was performed at Nassau University Medical Center, a major teaching institution in East Meadow, New York. Inpatient charts were reviewed consecutively until 50 patients prescribed warfarin alone, intravenous heparin alone, or LMWH alone were selected. We then determined which coagulation tests were performed each day for these patients by review of their computerized laboratory results. The costs of laboratory tests were obtained from the hospital laboratory and were used to calculate potential savings.
RESULTS: PT and PTT coagulation tests were requested together in all 50 patients. Seventeen patients on LMWH alone had 30 sets of PT/PTT performed (60 tests). Seventeen patients on intravenous heparin had 87 PTs performed. Twelve patients on warfarin had 60 PTTs performed. In total, 232 unneeded PT or PTTs were ordered in these 50 patients, or 4.6 per patient during hospitalization.
CONCLUSION: The review of the records of 50 medical inpatients found that PT and PTT were invariably requested together, despite a lack of indication. The 50 patients incurred a total of $2434 in unneeded costs. If representative of common clinical practice, significant cost savings may be possible. Education, computerization, and information on costs of individual tests may reduce unneeded investigations.