Article Text

Download PDFPDF

Wide variability in the sensitivity of APTT reagents for monitoring of heparin dosage.
  1. S Kitchen,
  2. I Jennings,
  3. T A Woods,
  4. F E Preston
  1. Royal Hallamshire Hospital, Sheffield.


    AIM: To assess the sensitivity of activated partial thromboplastin time (APTT) reagents for monitoring heparin dosage using data from the UK National External Quality Assessment Scheme (NEQAS) for blood coagulation. METHODS: Data were reviewed from four surveys using samples prepared by addition of heparin to normal plasma in vitro and from two surveys in which samples were prepared using plasma from patients receiving heparin therapy (ex vivo samples). RESULTS: For both in vitro and ex vivo samples, notable differences between APTT reagents with respect to heparin sensitivity were noted. This indicates that a uniform therapeutic range of 1.5-2.5 calculated by the APTT ratio may not be appropriate for all reagents. Reagent sensitivity in ex vivo samples was substantially different to that in in vitro samples. CONCLUSIONS: The results of this large series of laboratories clearly indicate that reagent specific therapeutic ranges may be necessary, and that samples prepared by the addition of heparin to normal plasma in vitro can be misleading and should not be used.

    Statistics from

    Request Permissions

    If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.