Plasminogen Activator Inhibitor 1, Activity
Label Mnemonic: PAI1
Epic code: LAB3869
Downtime form: A-1a Doctor/Provider Orders - Pathology Core and Specialty Care Nursery
Commercial Mail-out Laboratory
5231 RCP
Specimen Instructions:
Collect sample between 0800-1200.
Collection Medium:
Light Blue top tube 2.7 mL (Na Citrate)
Preferred Minimum: 1.5 mL platelet poor plasma.
Absolute Minimum: 1.0 mL platelet poor plasma (light blue tube top).
Rejection Criteria:
Serum, hemolyzed specimens; specimens that have been thawed and refrozen
Delivery Instructions:
Deliver to laboratory immediately after collection. Critical frozen.
Turn Around Time:
1-8 days upon receipt at reference laboratory
Reference Range:
By report
Test Limitations:
Plasminogen activator inhibitor-1 (PAI-1) is an inhibitor of 
tissue plasminogen activator (t-PA), a key enzyme in fibrinolysis. PAI-
1 is synthesized by endothelial cells, platelets, and hepatocytes. 
Three forms of PAI-1 have been identified. The first form is the active 
form, while the other two forms are inactive and latent. The main 
function of PAI-1 in hemostasis is to inhibit t-PA. As PAI-1 levels 
increase, active levels of t-PA decrease, causing impaired fibrinolytic 

Elevated levels of PAI-1 have been observed in deep-vein thrombosis and 
myocardial infarction, as well as in normal pregnancy and sepsis.

One unit of PAI-1 activity is defined as the amount of PAI-1 that 
inhibits one international unit of t-PA, as calibrated against the 
international standard for t-PA. This assay should be used for the 
quantitative determination of active PAI-1 in human plasma. This may be 
useful in the diagnosis of thrombotic disease.
CPT Code:
See Additional Information:
Specimens Requiring Immediate Delivery