Laboratory identification of Lupus Anticoagulants Using
the Combination of Activated Partial Thromboplastin Time
and Russell's Viper Venom at Two Phospholipid Concen
trations
BENJAPORN AKKAWAT,BSc*, VEENA CHANT ARANGKUL, BSc**,
PONLAPAT ROJNUCKARIN, MD, PhD*, JUMLONG JUNTIANG*
Affiliation : * Division of Hematology, Department of Medicine, Faculty of Medicine, Chulalongkom University, Bangkok 10330,
Thailand.
** Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Department oflntemal Medicine, University and IRCCS
Maggiore Hospital, Milan Italy.
AbstractThe most appropriate combination of tests for lupus anticoagulants (LA) is unknown. The
standard double centrifugation method to prepare plasma was inadequate for platelet elimination,
interfering with kaolin clotting time and mixing studies. In the present study, the percentage correction
of activated partial thromboplastin time (APTT) and Russell's viper venom time (RVVT) by high
compared with low concentrations of phospholipid was used for both screening and confirmation of
LA. Abnormality in either one was reported as positive. The specificity of the tests in 122 individuals
without LA was 100 per cent for RVVT and 96.7 per cent for APTT, which yielded false positive by
heparin. The mixing study was omitted from the authors' strategy without decreasing the specificity. In
795 patients with thrombosis, LA was detectable in 6.03 per cent. The sensitivity of diluted activated
partial thromboplastin time (dAPTT) and diluted Russell's viper venom time (dRVVT) alone, com
pared with the combination of the two was 83.3 per cent and 79.2 per cent respectively. Therefore, this
new test scheme is a simple, inexpensive and efficient method for Thai patients.
Keywords : Lupus Anticoagulants, Laboratory Identification, APTT, RVVT
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