Geisinger Medical Laboratories Test Catalog

HEPARIN, UNFRACTIONATED

• If the patient’s hematocrit (HCT) is >55%, the volume of anticoagulant in the tube must be adjusted. Contact a performing location for sodium citrate adjusted tubes or instruction for how to adjust the sodium citrate.
• When possible, use fresh venipuncture.
• Avoid prolong tourniquet time (< 1 minute) and hemolysis during collection as this will alter results.
• If indwelling catheter or butterfly collection device must be used, draw sample from a non-heparinized lumen or flush the line with 5 mL of saline and discard/use first 5-10 mL of blood for other purposes.
• Tubes should be >90% filled.
• Immediately mix gently after collection by inverting the tube end over end 5 to 6 times. Avoid vigorous mixing or additional inversion. Observe for the presence of clots or hemolysis and recollect if observed.

Therapeutic range: 0.3 - 0.7 IU/mL

Low antithrombin III levels may falsely lower levels. If three (3) consecutive subtherapeutic unfractionated heparin levels recommend checking antithrombin III level and if low consider antithrombin III replacement.

Anticoagulation with anti-Xa inhibitors (e.g. apixaban, rivaroxaban) causes false results. If the patient is on anti-Xa inhibitor prior to heparin therapy use an alternative method to monitor heparin.