Detection and quantification of lupus anticoagulants in plasma from heparin treated patients, using addition of polybrene

Several heparin neutralisers were tested, and polybrene was chosen for further testing. Unfractionated heparin and/or polybrene were added to normal plasma and to plasma from patients with or without lupus anticoagulant and clotting times compared before and after the additions. Lupus anticoagulant-positive patients were given 5000 IU i.v. of unfractionated heparin and plasma was collected just before and five minutes after the injection. Lupus Ratios were calculated after polybrene was added to the postinjection samples.The Lupus Ratio became slightly lower when polybrene was added to plasma without heparin. Plasma heparinised in vitro and plasma from patients that had received heparin, both had Lupus Ratios nearly identical to the Lupus Ratios calculated before any additions.By addition of polybrene to a final concentration of 7.9 μg/ml in test plasma, Lupus Ratio may be determined in lupus anticoagulant-negative as well as positive plasmas irrespective of the presence of heparin 0.0 – 1.3 U/ml.Lupus anticoagulants (LAs) are a heterogeneous group of antibodies directed against phospholipidbinding (PL-binding) proteins or complexes of PLs and proteins [1]. By definition, LAs prolong clotting times in one or several PL-dependent coagulation assays (APTT, RVVT, PT) [2,3].The lupus ratio (LR) test is an integrated test for LA, incorporating screening test, mixing studies, and confirmatory testing into one assay [4,5]. The LR test may be based on either one of the phospholipid-dependent clotting time assays APTT, RVVT, or dPT [4,6]. The presence of unfractionated heparin (UFH) in the sample may, however, prolong clotting times and thereby invalidate the diagnosis of LA. Schjetlein et al. tested 28 patients on treatment with UFH. 24 of these patients had false positive tests for LA in the APTT-based LR test, and 19 of the 28 patients had false positive tests in the RVVT-based LR test [4]. Liest？l et al. found that heparin concentrations in plasma exceeding 0.625 U/ml ga