The effect of lupus anticoagulant in the second-generation assay for activated protein C resistance.
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.
Ragland
Brian D
BD
University of Alabama at Birmingham, USA.
Reed
Cari E
CE
Eiland
Barbara M
BM
Tichenor
Patricia H
PH
Hudson
Christine L
CL
Fritsma
George A
GA
Adler
Brian K
BK
Marques
Marisa B
MB
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
D016682:Lupus Coagulation Inhibitor; D011933:Reagent Kits, Diagnostic; C095381:factor V Leiden; D005165:Factor V