Assay

Heparin Ratio

Key Words

Heparin, UF, unfractionated heparin, APTT

Specimen Collection

3.0ml Citrate (Green lid). 1.4ml Citrate for paediatric (Green lid). Fill to mark.

Turnaround time

4 hours.

Test indications

Unfractionated heparin dose monitoring (for LMW Heparin, use Low Molecular Weight Heparin anti-Xa assay instead)

Interferences

Lipaemia, haemolysis, anticoagulants, antiphospholipid syndrome. Samples will be processed up to 24 hours from the time of collection. However, samples older than 8 hours at processing may begin showing interferences due to sample degradation and should be interpreted with caution. The antibiotic oritavancin has been shown to react with certain coagulation reagents; it may artificially prolong the APTT for approximately 120 hours (5 days) post-dosage.

Reference Range

Therapeutic range: 1.5 - 2.5 R (Derived from Basu, D., et al. (1972). A prospective study of the value of monitoring heparin treatment with the activated partial thromboplastin time. New England Journal of Medicine, 287, 324–327.)

Minimum retesting interval

N/A