Plasminogen Activator Inhibitor 1 (PAI-1) Antigen

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Turnaround Time: 4 - 8 days
CPT Code:


Test Type: 0.5 mL Plasma, frozen
Reference Range:

4.0 − 43.0 ng/mL


Measure the quantity of PAI-1 in plasma, which may be useful in the determination of PAI-1 deficiency.6

Samples containing platelets prior to freezing will give erroneously high results due to the release of latent PAI-1 from platelet granules.

As PAI-1 is an acute phase reactant and also demonstrates diurnal variation, interpretation of results is difficult. Levels are highest in the morning. Deep vein thrombosis (DVT) and coronary artery disease (CAD) are associated with increased PAI-1 levels. Elevations have also been reported with diabetes mellitus, hypertension, obesity, insulin resistance, pregnancy, and with certain malignancies. Deficiency of PAI-1, an extremely rare and difficult diagnosis to make, has been associated with a bleeding diathesis. The PAI-1 antigen levels rise three- to sixfold during the third trimester of normal pregnancy. This is more pronounced in preëclamptic pregnancies. PAI-1 is the primary inhibitor of tissue plasminogen activator (tPA), a key enzyme in fibrinolysis. An increased plasma level of PAI-1 is associated with impaired fibrinolytic function. PAI-1 is found in several forms: active, inactive (latent), and complexed to tPA and urokinase plasminogen activator (uPA), all of which are measured in the PAI-1 antigen assay.

1. Adcock DM, Kressin DC, Marlar RA. Effect of 3.2% vs 3.8% sodium citrate concentration on routine coagulation testing. Am J Clin Pathol. 1997 Jan; 107(1):105-110. PubMed 8980376

2. Reneke J, Etzell J, Leslie S, Ng VL, Gottfried EL. Prolonged prothrombin time and activated partial thromboplastin time due to underfilled specimen tubes with 109 mmol/L (3.2%) citrate anticoagulant. Am J Clin Pathol. 1998 Jun; 109(6):754-757. PubMed 9620035

3. National Committee for Clinical Laboratory Standardization. Collection, Transport, and Processing of Blood Specimens for Coagulation Testing and General Performance of Coagulation Assays; Approved Guideline. 5th ed. Villanova, Pa: NCCLS; 2008. Document H21-A5:28(5).

4. Gottfried EL, Adachi MM. Prothrombin time and activated partial thromboplastin time can be performed on the first tube. Am J Clin Pathol. 1997 Jun; 107(6):681-683. PubMed 9169665

5. McGlasson DL, More L, Best HA, Norris WL, Doe RH, Ray H. Drawing specimens for coagulation testing: Is a second tube necessary? Clin Lab Sci. 1999 May-Jun; 12(3):137-139. PubMed 10539100

6. Brandt JT, Triplett DA, Alving B, Scharrer I. Criteria for the diagnosis of lupus anticoagulants: An update. On behalf of the Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibody of the Scientific and Standardisation Committee of the ISTH. Thromb Haemost. 1995 Oct; 74(4):1185-1190. PubMed 8560433

Collection Details:

Collection Instructions:

Blue-top (sodium citrate) tube.

Citrated plasma samples should be collected by double centrifugation. Platelet-poor plasma is needed. Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.1 Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio.2,3 The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood. A discard tube is not required prior to collection of coagulation samples.4,5 When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternate anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes. Centrifuge for 10 minutes and carefully remove 2/3 of the plasma using a plastic transfer pipette, being careful not to disturb the cells. Deliver to a plastic transport tube, cap, and recentrifuge for 10 minutes. Use a second plastic pipette to remove the plasma, staying clear of the platelets at the bottom of the tube. Transfer the plasma into a LabCorp PP transpak frozen purple tube with screw cap (LabCorp N° 49482). Freeze immediately and maintain frozen until tested. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.