Veripath Test Directory

Synonyms Heparin Anti-Xa Assay, Low Molecular Weight Heparin.
Description Heparin Anti-Xa assay is a test that is used for monitoring anticoagulant therapy with Low Molecular Weight Heparin in certain patients (e.g. Pediatrics, impaired kidney function, and pregnancy). This reaction is catalyzed by heparin. Dextran sulfate (OS) releases heparin which has bound to interfering factors and thus make it accessible to the assay. The quantity of Xa remaining is determined via the increase in absorbance at 405nm, using a chromogenic substrate in a kinetic test.
Specimen Requirements 
Container 3 mL 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, >2 hrs old (if not frozen), thawed plasma
Methodology Chromogenic
Reference Range See interpretive report.
CPT Code(s) 85520
Department Hemostasis/Coagulation
Contact Information Hemostasis Lab; 214-633-4959 Customer Service: 214-633-0400, Toll Free 1-877-887-8136.
Turn Around Time2 hours
Performed Sunday - Saturday
Performed by Hemostasis Lab
Updated/Reviewed 07/25/2016