Prothrombin Time Mix With Reflex to Lupus Inhibitor
Orderable EAP code:
Billable EAP Codes:
CPT Codes:
Lab Section:
Turnaround Time:
Routine: 2 Hours
Urgent: 1 Hour
Test Schedule:
Mixes performed 7 days a week in Core lab. Samples received before 1:30 pm are run the same day; after 1:30 pm, samples are processed the next day. Batched 2 times per week. Call 503-494-7383 if STAT.
Units:
Specimen Requirements:
3 LIGHT BLUE top tube, 3.2% sodium citrate or four (4) 1 mL frozen sodium citrate plasma aliquots. Draw volume is critical due to the liquid anticoagulant. Allow tubes to fill by vacuum. For tubes with a rubber stopper, fill to the line on the label. For tubes with a plastic (hemogard) cap, the fill level is above the top of the label. If drawing with a syringe, do not remove the vacutainer stopper; insert the needle through stopper and allow the tube to fill by vacuum.
Hemostasis & Thrombosis lab sodium citrate specimens must be processed and frozen within 2 hours of specimen collection. OHSU clinics must cab the specimen to the Core Lab, Hatfield Research Center, 9th Floor (room 9D20) if processing is delayed or not possible on site. A phone call is helpful to alert the lab at 503-494-7383. Detailed instructions are included in this manual under Specialized Lab Services, Hemostasis & Thrombosis section.
Pediatric Specimen Requirements:
3 pediatric 1.3 mL LIGHT BLUE top tubes, 3.2% sodium citrate or two 0.5 mL frozen sodium citrate plasma aliquots. For pediatric patients requiring multiple coagulation tests, please call 503-494-7383 regarding draw volumes.
Reference Range:
Normal Pool, 0 min: 11.9 to 16.0 sec.
Normal Pool, 60 min: 11.9 to 16.0 sec.
Lupus anticoagulant testing - see separate test instructions.
Comments:
Avoid warfarin (Coumadin) therapy for 2 weeks and heparin/DOAC/DTI therapy for 2 days prior to test.
The assay is used to distinguish between circulating and coagulation factor deficiency when PT is prolonged. Test is a screening test for the lupus anti-coagulant. Typically, a patient is identified with a prolonged PT without a history of bleeding, or perhaps with a history of thrombosis or miscarriage. Failure to correct a prolonged PT with 1:1 mix suggests a circulating inhibitor. A positive-delete mixing study indicating an inhibitor should be followed by studies to determine whether the inhibitor is a true antibody (i.e. anti-Factor V) or an anti-phospholipid antibody (lupus anticoagulant). Anticoagulant screening may be reflexively performed to exclude drug effects.
Methodology: Clot-based on prolongation of PT assay.
Synonyms:
PT 1:1 Mix, PTM, 50:50, 1:1 Mix, PT Mix