Veripath Test Directory

Epic Test Name Unfractionated Heparin Assay
Synonyms Heparin Anti-Xa assay
Description Heparin considerably acclerates the inactivation of coagulation Factor Xa and thrombin by antithrombin (AT). For this reason unfractionated and low-molecular-weight heparin preparations are widely used as therapeutic anticoagulants. Due to numerous influences, the effect of an identical dose of heparin varies from patient to patient. Using a Heparin anti-factor Xa protocol, it is possible to accurately monitor therapy with unfractionated heparin when reliable monitoring with PTT is not possible (e.g., high Factor VIII, fibrinogen levels, antithrombin deficiency, elevated PTT at baseline due to e.g., lupus anticoagulant, strong antiphospholipid antibodies, etc.)
Specimen Requirements 
Container Light blue (3.2 % sodium citrate) collection tube
Specimen Type Blood
Preferred Collection Volume 3 mL
Minimum Collection Volume Adult: 2 mL, Neonates : 2 mL
Collection Instructions When drawing specimens for coagulation testing, always draw a "pilot" tube (7-10ml plain red top tube), completely filled. This removes tissue fluid contamination. Samples should be obtained from peripheral vein whenever possible. If drawn from indwelling catheter, the line should be flushed with 15mL of saline. After irrigation, a "pilot" tube should be drawn and discarded.
Specimen Handling In-house patients, transport at room temperature.
Out-side client, follow collection instructions and the steps below:
1. Spin light blue top tube. Remove plasma avoiding platelet/buffy coat layer. Spin plasma again to remove top portion of plasma ans place 1mL of PLATELET-POOR PLASMA in plastic tube. (Glass tube unacceptable). Double-centrifugation is critical for accurate results as platelet contamination may cause erroneous results.
2. Plasma must be frozen within 4 hours of collection. CRITICAL WARNING: Specimens must remain frozen until ready to test. Submit separate aliquots when multiple tests are ordered on the same patient specimen.
Rejection Criteria Hemolysis, clotted, short sample, >4 hrs old (if not frozen), thawed plasma, heparin contamination.
Methodology Chromogenic
Reference Range See interpretive report.
CPT Code(s)
Department Hemostasis/Coagulation
Contact Information Hemostasis Lab; 214-633-4959 Customer Service: 214-633-0400, Toll Free 1-877-887-8136.
Turn Around TimeIn-house - 2 hours; Outside clients1 day.
Performed Sunday-Saturday
Performed by Hemostasis Lab
Updated/Reviewed 07/25/2016