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Abstract
For the monitoring of unfractionated heparin therapy (UFH) there are numerous pre-analytical, analytical and biological variables associated with the use of activated partial thromboplastin time (APTT), so the traditional range of 1.5-2.5 times the baseline value can lead to inadequate heparinization, resulting in thrombosis. Guidelines recommend to obtain the heparin therapeutic range (HTR) with ex vivo samples from patients under continuous heparin infusion therapy, measuring heparinemia by anti-Xa assay, since when in vitro UFH spiked plasmas are used, an overestimation of the therapeutic range is noted. The objective of this study was to compare the results of HTR obtained using ex vivo samples and in vitro heparin spiked normal plasma samples. HTR for ex vivo samples resulted in 56-87 sec by anti-Xa assay. For in vitro spiked samples HTR was 55-127 sec. Using an alternative in vitro protocol correlating the APTT with UFH concentration between 0.2 and 0.4 IU/ ml, the HTR was 55-85 sec. The results also showed that there is an overestimation of HTR with the in vitro protocol especially at high concentrations, whereas the lower value of the range does not have significant differences when we compared both methods. Laboratories that do not have anti-Xa assay could obtain an estimate of the lower value of the HTR with an alternative protocol in vitro.
References
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