The use of frozen-thawed platelet-derived phospholipids as a confirmatory test for the diagnosis of lupus anticoagulants. Comparison with two commercial confirmatory system tests.

Lupus anticoagulants (LAs) belong to acquired circulating anticoagulants interfering with phospholipid-dependent coagulation tests. Owing to the remarkable variability among patients, SSC guidelines recommend more than one test to detect and confirm the presence of LAs. However, this is an expensive procedure and greatly raises the work load of the laboratory. A standardised platelet-derived phospholipid preparation was obtained and platelet neutralisation (PNP) procedures with APTT and DRVVT reagents were performed on plasmas from 16 patients with LAs and from 41 control subjects. In comparisons, STAclot-PNP(R) and DVVconfirm(R) clotting assays were conducted. PNP by using APTT or DRVVT reagents showed intra-assay coefficient of variation of 1.6 and 1.8%, whereas inter-assays coefficient of variations were 6.8 and 5.1%, respectively. A complete concordance was achieved between STAclot-PNP(R) and PNP by using APTT reagents and between DVV-confirm(R) and PNP with DRVVT reagents, demonstrating a high reliability of both the PNP-based assays. This consistency indicates that the standardised platelet-derived phospholipid preparation obtained allows for reliable, reproducible, and cheap PNP-based confirmatory assays for LAs testing. (C) 1999 Elsevier Science Ltd. All rights reserved.