Evaluation of a new protamine titration method to assay heparin in whole blood and plasma

Annette J. Schlueter, Beverly J. Pennell, John D. Olson

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


When unfractionated heparin is used for therapeutic anticoagulation, the heparin effect must be monitored to avoid thrombotic or hemorrhagic complications. The ability of a factor Xa inhibition (XaI) assay was compared with that of a low-level heparin protamine titration (LLHPT) assay to measure the concentration of heparin after heparin was added in vitro to specimens of plasma and whole blood. Heparin effect on the activated partial thromboplastin time also was assessed in the same specimens. The XaI and LLHPT assays had comparable precision and provided linear results over a wide range of heparin concentrations. Both assays slightly underestimated the total amount of heparin added to the specimens. The most rapid test was the whole blood LLHPT assay; this test therefore may be useful for bedside monitoring of heparin. A significant disadvantage of the LLHPT assay was the large sample size required to perform it. These results provide in vitro evidence that the XaI and LLHPT assays can provide equally precise monitoring of heparin concentration.

Original languageEnglish (US)
Pages (from-to)511-520
Number of pages10
JournalAmerican journal of clinical pathology
Issue number5
StatePublished - May 1997


  • Factor Xa inhibition assay
  • Heparin
  • Point-of-care testing
  • Protamine titration

ASJC Scopus subject areas

  • Pathology and Forensic Medicine


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