title: The effect of lupus anticoagulant in the second-generation assay for activated protein C resistance.
abstract: 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.affiliation: University of Alabama at Birmingham, USA.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Ragland
authors.forename: Cari E
authors.initials: CE
authors.lastname: Reed
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Eiland
authors.forename: Patricia H
authors.initials: PH
authors.lastname: Tichenor
authors.forename: Christine L
authors.initials: CL
authors.lastname: Hudson
authors.forename: George A
authors.initials: GA
authors.lastname: Fritsma
authors.forename: Brian K
authors.initials: BK
authors.lastname: Adler
authors.forename: Marisa B
authors.initials: MB
authors.lastname: Marques
mesh_terms: D020016:Activated Protein C Resistance / Q000097:blood / Q000175:diagnosis*; D000328:Adult; D001780:Blood Coagulation Tests / Q000379:methods*; D005165:Factor V / Q000032:analysis; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D016682:Lupus Coagulation Inhibitor / Q000097:blood / Q000502:physiology*; D008403:Mass Screening / Q000379:methods; D011237:Predictive Value of Tests; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D016682:Lupus Coagulation Inhibitor; D011933:Reagent Kits, Diagnostic; C095381:factor V Leiden; D005165:Factor V