The effect of lupus anticoagulant in the second-generation assay for activated protein C resistance

Academic Article


  • The activated protein C resistance (APCR) assay is the test of choice to screen for factor V Leiden. We evaluated the effect of lupus anticoagulant on the baseline clotting time of the second-generation APCR assay with plasma samples from 54 patients to determine whether a falsely low APCR ratio could be predicted. We also assessed whether a modification of the assay could make it more reliable in the presence of strong lupus anticoagulants. Of 54 plasma samples, 5 yielded a false-positive APCR ratio, and all 5 had a prolonged baseline clotting time. Further dilution (1:40) of the plasma samples in factor V - deficient plasma led to correction of the APCR ratio and did not affect the sensitivity of the test for factor V Leiden. Our data support that the baseline clotting time is a good predictor of a false-positive APCR test result and should be checked before calculating the ratio. The modified APCR assay reliably identified the false-positive ratios and could be used to screen for factor V Leiden in samples with strong lupus anticoagulant.
  • Authors

    Digital Object Identifier (doi)

    Author List

  • Ragland BD; Reed CE; Eiland BM; Tichenor PH; Hudson CL; Fritsma GA; Adler BK; Marques MB
  • Start Page

  • 66
  • End Page

  • 71
  • Volume

  • 119
  • Issue

  • 1