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Related Experiment Videos

Normal functional protein S activity does not exclude protein S deficiency.

Marc A Rodger1, Marc Carrier, Muriel Gervais

  • 1Department of Medicine, University of Ottawa, Ottawa, ON, Canada. mrodger@ohri.ca

Pathophysiology of Haemostasis and Thrombosis
|December 8, 2004
PubMed
Summary

A normal functional Protein S (PS) activity test does not rule out PS deficiency. Free antigenic PS testing remains essential for accurate laboratory diagnosis of PS deficiency.

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Area of Science:

  • Hematology
  • Clinical Chemistry

Background:

  • Protein S (PS) deficiency is a risk factor for venous thrombosis.
  • PS deficiency is classified into three phenotypes based on antigenic levels and functional activity.
  • All PS deficiency phenotypes should exhibit reduced activated protein C cofactor activity.

Purpose of the Study:

  • To evaluate if a normal functional PS activity assay can replace free antigenic PS testing.
  • To determine the diagnostic accuracy of functional PS activity testing in identifying PS deficiency.

Main Methods:

  • Comparison of functional PS activity assay results with free antigenic PS testing.
  • Statistical analysis of sensitivity, specificity, and predictive values of the functional assay.

Main Results:

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  • The functional PS activity assay demonstrated a sensitivity of 45.5% and specificity of 95.3%.
  • Negative predictive value was 88.6%, and positive predictive value was 68.5%.
  • A normal functional assay result did not exclude the presence of free antigenic PS deficiency.

Conclusions:

  • Functional PS activity testing alone is insufficient for the laboratory diagnosis of PS deficiency.
  • A normal functional PS activity result cannot eliminate the need for free antigenic PS testing.
  • Functional PS activity testing should not be used as a sole screening test for PS deficiency.