title: A low volume specimen container suitable for monitoring the aPTT of heparinized patients.
abstract: Differences in the activated partial thromboplastin time (aPTT) were shown when blood taken from patients receiving intravenous heparin therapy was collected into 5 ml and 1 ml citrate containers. Mean aPTTs were 27% shorter with the plasma from the 1 ml citrate containers (n = 23). These results were paralleled by a 37% reduction in the mean heparin concentration (n = 11) and a 77% increase in the mean platelet factor 4 (PF4) concentration (n = 7). This phenomenon is due to increased platelet activation and subsequent increased heparin neutralization in the 1 ml citrate container. In an attempt to overcome this, the citrate was removed from a 1 ml container and replaced with a buffered tri-sodium citrate solution containing theophylline, adenosine and dipyridamole anticoagulant (CTAD). Blood from heparinized patients taken into both 5 ml citrate and 1 ml CTAD showed a correction of the shortening artefact in the low volume container. The mean aPTT of plasmas from the 1 ml CTAD container showed an increase of 10% compared with the 5 ml citrate. There was no significant difference in the mean heparin or PF4 concentrations of blood taken into either container. The 1 ml CTAD tube described is a suitable collection container for monitoring heparin in neonates or patients who are difficult to venepuncture and overcomes the neutralization of heparin in part filled low volume containers.
authors.affiliation: Department of Pathology, Prince Charles Hospital, Chermside, Queensland, Australia.
authors.forename: M J
authors.initials: MJ
authors.lastname: Ray
authors.forename: P A
authors.initials: PA
authors.lastname: Carroll
authors.forename: S J
authors.initials: SJ
authors.lastname: Just
authors.forename: G A
authors.initials: GA
authors.lastname: Hawson
mesh_terms: D001800:Blood Specimen Collection / Q000295:instrumentation*; D002951:Citrates; D019343:Citric Acid; D006493:Heparin / Q000097:blood / Q000627:therapeutic use*; D006801:Humans; D010314:Partial Thromboplastin Time; D010978:Platelet Factor 4 / Q000032:analysis
chemical_list: D002951:Citrates; D019343:Citric Acid; D010978:Platelet Factor 4; D006493:Heparin