What is the value of a false positive VDRL test?
The VDRL test measures agglutination (flocculation) of lipid particles that contain cholesterol and the negatively charged phospholipid cardiolipin. aPL abs bind to the cardiolipin in these particles and cause flocculation, indistinguishable from that seen in patients with syphilis. A false-positive VDRL may be a clue to the presence of other aPL abs, but in and of itself, is not a good way to screen for the presence of aPL abs. A false-positive VDRL or rapid plasma reagin is seen in, at most, 50% of patients with aPL abs and as such, is not recommended as an additional laboratory test in assessing an individual with suspected APS. Patients with only a false-positive VDRL and no other aPL abs are not at increased risk for clots or fetal loss.
