We’ve had three posts and several comments regarding lupus anticoagulant (LA) mixing studies since March. These are…
- March 18, 2012: Test for LA When Mixing Study Corrects?
- March 22, 2012: Mixing Study Results: Long PT and PTT
- April 3, 2012: More on LA Mixing Studies
In these posts several experts held that it is necessary to continue with LA detection studies even when the initial mixing study demonstrates correction. Their rationale is that a weak LA is “washed out” or neutralized in a 1:1 mix, and thus may go undetected. The LA may yet be detected and confirmed using the dilute Russell viper venom time (DRVVT) “screen and confirm” and the partial thromboplastin time (PTT)-based hex-phase phospholipid neutralization method.
On Friday, May 4, 2012, Thomas Ortel, MD, PhD, Director, Anticoagulation Management Service and, Duke Clinical Coagulation and Platelet Immunology Laboratories, Duke University Medical Center, Durham, NC, spoke on LA profiling at the Thrombosis and Hemostasis Summit of North America in Chicago. His position parallels those of the experts who contributed to the previous three posts. He contends that it is necessary to perform the LA detection assays even when the mixing study corrects, given the potential for a weak LA. He further recommends that the reagent pooled normal plasma mixing study always be included as part of the profile. This is because the original test order is most likely based upon some abnormal finding and the mixing study may detect and identify some additional, otherwise undetected abnormality. The addition of mixing study results to the DRVVT and PTT screen/confirm results provides a complete picture and helps develop the final findings. Dr. Ortel added in a private follow-up that in most cases, he sees mixing study results whose “correction” is borderline or equivocal.