For our October, 2018 Quick Question we asked, “For lupus anticoagulant testing, how do you express the DRVVT screen and confirm results?”
Here are the answers from 36 respondents:
a. Ratio of screen to confirm: 17 = 47%
b. Ratio of screen to confirm normalized to MRI: 17 = 47%
c. Difference of screen and confirm in seconds: 0
d. Difference of screen and confirm in seconds normalized to MRI: 2 = 6%
The even split between “normalizers” and “non-normalizers” illustrates a difference of opinion in our community. CLSI standard H60 requires normalization for both the CRVVT-based and the PTT-based lupus anticoagulant test profiles, quoting several sources. The “non-normalizers” quote data that show normalizing rarely affects the diagnosis but adds unnecessary mathematical complexity. The debate is likely to continue. I’ve attached article summarized in Mr. McGlasson’s comment below:
As an aside, the term “screen” is a poor choice, as a screening test is a test employed on unselected individuals, whereas lupus anticoagulant testing is typically ordered for an indication such as pregnancy loss or unprovoked thrombotic events, and is often performed in follow-up to a prolonged PTT or an initial mixing study. Looking for a better term than screen, I’ve seen “initial” or “first-tier.” What is your preference?