Abstract
The International Society on Haemostasis and Thrombosis (ISTH) and the British Committee
for Standards in Haematology (BCSH) have recently updated their lupus anticoagulant
(LA) detection guidelines. The Clinical and Laboratory Standards Institute (CLSI)
subsequently will publish its first LA guideline. General agreement exists on issues
such as sample preparation, the use of dilute Russell viper venom time (dRVVT) in
diagnostic repertoires, the use of normalized ratios, calculations to demonstrate
phospholipid dependence, calculations to demonstrate inhibition, and interpretive
reporting. The ISTH recommendation to employ only dRVVT and activated partial thromboplastin
time is not mirrored in the BCSH and CLSI documents. The potential for false negatives
in mixing tests is acknowledged by all panels, yet they remain mandated by ISTH as
there are occasions when they are crucial to diagnostic accuracy. BCSH indicates that
a negative mixing test need not exclude the presence of a LA, and CLSI reprioritizes
test order to screen-confirm-mix, the latter being considered unnecessary in specific
circumstances. Opinions in the guidelines differ on setting cutoff levels (i.e., 97.5th
vs. 99th percentile for normally distributed data). All guidelines cover testing of
anticoagulated patients, more detail being given by BCSH and CLSI, who suggest that
Taipan snake venom time is a useful adjunct test in patients receiving vitamin K antagonists.
Although complete agreement is not apparent, the guidelines represent significant
moves toward engendering common practices.
Keywords
lupus anticoagulants - guidelines - dilute Russell viper venom time - activated partial
thromboplastin time
