George has had several conversations with frequent contributor and international expertDave McGlasson (Wilford Hall USAF Medical Center, San Antonio) about normalizing the DRVVT ratio on the laboratory’s DRVVT mean of the reference interval in accordance withZhang L, et al: A simplified algorithm for the laboratory detection of lupus anticoagulants. Am J Clin Pathol 2005;124:894–901. The author states, “The normalized ratio is recommended to correct for differences in instrument-reagent combinations and to improve discrimination between normal and low-positive LA samples. The formula for normalization is attached in this link: DRVVT Normalization Ratio.
In an email conversation with Dave, frequent contributor Dr. Emmanuel Favaloro(Australia) wrote: “We have always used normalised ratios. It doesn’t make sense to me not to, since the baseline values for the screen and confirm are invariably different. Moreover, they will change slightly with different batches of reagents and different normal pools. On the other hand, if you have established your normal ranges based on non-normalised data you might be OK.”
The purpose for this post is to ask you, do you know about normalization of the DRVVT ratio, do you use it, do you advocate for it, and what advantages does the ratio provide?