Key result
Portable and central lab APTT therapeutic ranges differ by ~12 seconds during heparin monitoring.
Why the study?
This study aimed to measure the difference in therapeutic ranges of activated partial thromboplastin time (APTT) between two laboratory devices used for heparin monitoring.
Does the use of different laboratory devices for APTT measurement result in different therapeutic ranges in inpatients receiving intravenous unfractionated heparin?
Observational (n=30)
No
Does the use of different laboratory devices for APTT measurement result in different therapeutic ranges in inpatients receiving intravenous unfractionated heparin?
A fixed APTT ratio for monitoring unfractionated heparin may result in significant underanticoagulation, necessitating instrument-specific therapeutic ranges.
Device-specific APTT ranges may be required for heparin; leaves open whether fixed ratios cause underanticoagulation in practice.
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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Taylor et al. (1999) conducted an observational in Myocardial infarction, unstable angina, deep venous thrombosis, or pulmonary embolism treated with intravenous unfractionated heparin (n=30). Portable whole blood assay device for APTT vs. Central laboratory plasma assay device and conventional 1.5-2.5 times mean normal APTT ratio was evaluated on Difference in therapeutic activated partial thromboplastin time (APTT) ranges between portable and central laboratory devices (MD 12 sec, p=<0.006). Portable and central laboratory APTT devices yielded significantly different therapeutic ranges (56-73 vs 61-93 sec; mean absolute difference 12 ± 20 sec, p<0.006) during heparin monitoring.
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