Screening with the activated protein C resistance assay yields significant savings in a patient population with low prevalence of factor V leiden.

Testing for factor V Leiden can be performed with a molecular assay or a test for activated protein C resistance. We noted that physicians in our institution tended to order the molecular test 80% of the time, but the prevalence of the mutation in our patient population was less than 10%. Consequently, we decided to introduce the activated protein C resistance assay in house and consistently use it for screening before the more expensive genetic test and to negotiate a discounted charge for the latter at a reference laboratory.

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.