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Primary Name Prothrombin Time Mixing Study
Synonym Protime mixing study
Synonym Prothrombin time substitution
Contraction PT mix
Contraction PT substitution
Contraction --
UAB Procedure Number 2500135
CPT Code 85611
Specimen Collect two (2) blue-stopper tubes (3.2% sodium citrate), filled to specified volume. Do not underfill or overfill.

Specimen Management Centrifuge blue-stopper tube within one (1) hour of collection, separate plasma and test or quick-freeze at -70°C.
Specimen Accepted Daily including weekends
Test Performed Monday through Friday
Available Stat? No.
Description A PT mixing study may be ordered when the PT is prolonged in the absence of anticoagulant therapy. The test is preceded by a thrombin time to detect therapeutic heparin or a direct thrombin inhibitor. Patient plasma is mixed with normal plasma, the mixture is incubated, and the PT is repeated. If the mixture's PT result does not correct, the patient may have an inhibitor such as a lupus anticoagulant. If the mixture's PT result corrects, the patient may have a coagulation factor deficiency. The results of the PT mixing study are used to direct further studies in consultation with the ordering physician.
Reference Interval *Correction suggests factor deficiency.
*No correction suggests presence of an inhibitor.
Follow-up Test *If PT corrects, follow with factor assays.
*If PT does not correct, follow with lupus anticoagulant testing.
Associated With Coagulation factor inhibitors
Associated With Bleeding disorders
Associated With Venous thrombosis
Associated With Lupus anticoagulant

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