Standardization of methods for measuring plasminogen activator inhibitor activity in human plasma

W. L. Chandler, S. C. Loo, S. V. Nguyen, G. Schmer, J. R. Stratton

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


We have standardized the measurement of plasminogen activator inhibitor type 1 (PAI-1) activity in plasma. One-chain tissue-type plasminogen activator (t-PA; EC; final activity, 5 int. units/mL) was incubated with plasma (final dilutions 1:4 to 1:40) in phosphate buffer (pH 7.4, ionic strength = 0.15) for 15 min at 37°C, followed by acidification and measurement of residual t-PA activity by an amidolytic method. The PAI-1 activity assay was 98% specific for PAI-1 activity in samples from both pregnancy and nonpregnancy, and varied linearly with added plasma volume when the percent inhibition of t-PA was between 8% and 50%. For the standardized method, analytical recovery was 93 ± 5%, the detection limit was 1.6 arbitrary units per milliliter (1 arb. unit of PAI-1 activity = inhibition of 1 in. unit of t-PA activity), and total imprecision was 10.2 (SD 0.7) arb. units/mL (CV = 7%, n = 20). The average PAI-1 activity in 10 healthy individuals drawn between 0800 and 1000 hours was 23.9 ± 15.4 arb. units/mL. Compared wtih the standardized assay, two of three previously described assays underestimated PAI-1 activity in plasma by 77% and 85%, respectively.

Original languageEnglish (US)
Pages (from-to)787-793
Number of pages7
JournalClinical Chemistry
Issue number5
StatePublished - 1989

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Biochemistry, medical


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