Taylor CT, Petros WP, Ortel TL. Two instruments to determine activated partial thromboplastin time: implications for heparin monitoring.
Pharmacotherapy 1999;
19:383-7. [PMID:
10212007 DOI:
10.1592/phco.19.6.383.31039]
[Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
STUDY OBJECTIVE
To measure the difference in therapeutic ranges of activated partial thromboplastin time (APTT) between two laboratory devices.
DESIGN
Prospective, controlled laboratory study.
SETTING
University-affiliated hospital.
PATIENTS
Thirty inpatients receiving intravenous unfractionated heparin for treatment of myocardial infarction, unstable angina, deep venous thrombosis, or pulmonary embolism.
INTERVENTIONS
Therapeutic APTT ranges were determined by a portable (whole blood assay) and a central laboratory device (plasma assay) based on heparin serum concentrations. They were compared with APTT ranges equivalent to 1.5-2.5 times the mean normal determination.
MEASUREMENTS AND MAIN RESULTS
The central laboratory and portable devices produced therapeutic ranges of 61-93 and 56-73 seconds, respectively. Both differed from conventional therapeutic ratios of 1.5-2.5 times the mean normal (41-68 sec). Mean absolute APTT differences between instruments were statistically significant (12 +/- 20 sec, p<0.006), and 58% of paired APTT values differed by more than 10 seconds.
CONCLUSION
A fixed APTT ratio as a goal for monitoring unfractionated heparin may result in significant underanticoagulation. Individual therapeutic APTT ranges must be reported for each instrument if more than one is used for heparin monitoring.
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