Clinical Lab Handbook

Specimen must arrive within 24 hours of draw.

Container/Tube: Light blue-top (3.2% sodium citrate) tube

Specimen Volume: 2.5 mL of sodium citrate plasma

Transport Temperature: Ambient

Collection Instructions: If there is a delay in transport of ≥24 hours, spin down, separate plasma and send specimen frozen in plastic vial.

Note: 1. Excessively high or low hematocrit will affect results.

2. Tube must be completely filled to ensure proper ratio of blood to anticoagulant and to avoid erroneous results.

The prothrombin time test (PT) is a global screening test with three major applications. These include 1) detection of single or combined deficiencies of the extrinsic coagulation pathway indicative of hereditary and acquired coagulation disorders, liver disease or vitamin K deficiency; 2) monitoring test for oral anticoagulant therapy; and 3) assay for specific extrinsic coagulation factors.

Thromboplastin and calcium ions are combined with test plasma at 37°C; the PT is the time, in seconds, required for a fibrin clot to form.

Critical value (automatic call-back): >5.0 INR

Monday through Sunday

Available STAT

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