Coagulation
Coagulation laboratory tests
Plasminogen activator antigen-1
Author: Jeremy C. Parsons, M.D.
Last author update: 1 November 2012
Last staff update: 23 September 2020
Copyright: 2002-2025, PathologyOutlines.com, Inc.
PubMed Search: Plasminogen activator antigen-1
Cite this page: Parsons JC. Plasminogen activator antigen-1. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/coagulationPAI1.html. Accessed January 10th, 2025.
Definition / general
- Uncommon test; perform if strong evidence of familial bleeding disorder, but normal results for von Willebrand disease or possibly if unexplained premature myocardial infarction
- May predict severe hepatic veno-occlusive disease after allogeneic bone marrow transplantation (Br J Haematol 2002;118:1087)
- Not a known risk factor for hypercoagulability (Arch Pathol Lab Med 2002;126:1401), although high levels are associated with arterial thrombosis; low levels are associated with rare familial bleeding disorder
- Has circadian rhythm with highest values in morning; in one study, mean level was 23 ng/mL at 9 am vs. 10 ng/mL at 4 pm; also is acute phase reactant, so don’t measure immediately following thrombosis; also elevated during pregnancy
Laboratory
- Collection: collect blood from steadily flowing venipuncture, discard first 3 - 5 mL (if this is the only test) and avoid platelet contamination of plasma (platelets contain PAI1) by separating plasma from cells or storing on ice
- Reject specimen if antifibrinolytic agent is present in specimen
- Reference range: 4 - 40 ng/mL for antigen assay, 0 - 12 units/mL for functional assay
- Functional assay: add patient plasma to known amount of urokinase / tPA, which binds to patient PAI1; residual urokinase is detected by adding plasminogen, which converts it to plasmin, which cleaves a chromogenic substrate; amount of released color is inversely proportional to patient PAI1 (inhibitors of antiplasmin and plasmin are present to prevent their interference)
- ELISA (antigen) assay: also available
