The Effect of Lupus Anticoagulant in the Second-Generation Assay for Activated Protein C Resistance

Brian D. Ragland, Cari E. Reed, Barbara M. Eiland, Patricia H. Tichenor, Christine L. Hudson, George A. Fritsma, Brian K. Adler, Marisa B. Marques
2003 American Journal of Clinical Pathology  
A b s t r a c t 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
more » ... e-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 falsepositive ratios and could be used to screen for factor V Leiden in samples with strong lupus anticoagulant.
doi:10.1309/1gn6ntm7bqap8vkx pmid:12520699 fatcat:6lxucrvegnhpxnmuxpre4uhrpe