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Test Code LAB0221183 Protime Mixing Studies

Methodology

Photometric Clot Detection

 

Screening test to detect a deficiency of 1 or more of the clotting factors of the extrinsic coagulation system (I,II,V,VII, X) due to hereditary deficiency or acquired conditions such as liver disease, vitamin K deficiency, or a factor inhibitor.

 

A thrombin time is run on patient's sample before proceeding with the mixing study to rule out heparin contamination  in the specimen.

Performing Laboratory

CentraCare Laboratory Services

Specimen Requirements

Specimen Type: Plasma

Container/Tube:  Two Light-blue top (3.2% sodium citrate) tube, properly filled. Use 2.7 ml or 5 ml tube.

Specimen Volume:3 mL

Collection Instructions:

1.Tube must be full.

2. If less than 24 hours until testing, ambient whole blood is preferred.

3. If there is a delay in testing of >24 hours, centrifuge for 10 minutes at 3,000 rpm, freeze plasma immediately at -20 0 C and send frozen  in plastic vial.

Specimen Transport Temperature

Ambient <24 hours

Frozen >24 hours

Reference Values

NORMAL PT

9.4-12.5 seconds
INR (stable oral anticoagulant therapy)
Std Rx: 2.0-3.0
High intensity Rx: 2.5-3.5
Critical value (automatic call-back): INR >4.0

 

Correction of the PT mix to within the normal reference range usually indicates a coagulation factor deficiency. If the prolonged PT is due to an inhibitor (specific coagulation factor inhibitor, lupus anticoagulant, heparin), the PT mix typically fails to correct a prolonged PT.

Day(s) Test Set Up

Monday through Sunday

Test Classification and CPT Coding

85610 PT

85670 Thrombin Time