To Mix or Not to Mix in Lupus Anticoagulant Testing? That is the Question

Abstract

Mixing patient and normal plasma has been used for many years to assist with making decisions on which direction to proceed for further investigation of abnormally prolonged coagulation tests, namely, either individual coagulation factor measurement or the search for circulating anticoagulants. Mixing tests, however, gained wide acceptance only after the so-called lupus-like anticoagulant (LA) phenomenon was described and were, therefore, included in the guidelines for LA detection issued by the working group of the International Society on Thrombosis and Haemostasis. Important though they may be considered, the dispute between those who advocate the use of mixing tests and those who deny their superiority (or their need) for LA detection is difficult to resolve. This article aims to provide a balanced view on this dispute. Based on the limited information provided by the literature one may conclude that the disadvantages of performing mixing studies are the fact that (1) they are time-consuming; (2) they require a suitable source of normal pool plasma; and (3) weak LA may be lost at diagnosis due to the dilution of index plasma into normal pooled plasma. On the contrary, performing mixing tests makes the occurrence of false-negative LA in patients who present with the so-called “lupus cofactor phenomenon” relatively unlikely and, therefore, justifies their performance even though the frequency of the occurrence of this phenomenon in LA-positive patients is still unknown.

Keywords

mixing tests - lupus-like anticoagulants - coagulation - anticoagulant testing

• References

• 1 Margolius Jr A, Jackson DP, Ratnoff OD. Circulating anticoagulants: a study of 40 cases and a review of the literature. Medicine (Baltimore) 1961; 40: 145-202
• 2 Conley CL, Hartmann RC. A hemorrhagic disorder caused by circulating anticoagulant in patients with disseminated lupus erythematosus. J Clin Invest 1952; 31: 621-622
• 3 Bowie EJ, Thompson Jr JH, Pascuzzi CA, Owen Jr CA. Thrombosis in systemic lupus erythematosus despite circulating anticoagulants. J Lab Clin Med 1963; 62: 416-430
• 4 Rai RS, Regan L, Clifford K , et al. Antiphospholipid antibodies and beta 2-glycoprotein-I in 500 women with recurrent miscarriage: results of a comprehensive screening approach. Hum Reprod 1995; 10 (8) 2001-2005
• 5 Brandt JT, Triplett DA, Alving B, Scharrer I. Criteria for the diagnosis of lupus anticoagulants: an update. On behalf of the Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibody of the Scientific and Standardisation Committee of the ISTH. Thromb Haemost 1995; 74 (4) 1185-1190
• 6 Pengo V, Tripodi A, Reber G , et al; Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibody of the Scientific and Standardisation Committee of the International Society on Thrombosis and Haemostasis. Update of the guidelines for lupus anticoagulant detection. J Thromb Haemost 2009; 7 (10) 1737-1740
• 7 Rosner E, Pauzner R, Lusky A, Modan M, Many A. Detection and quantitative evaluation of lupus circulating anticoagulant activity. Thromb Haemost 1987; 57 (2) 144-147
• 8 Chang SH, Tillema V, Scherr DA. A “percent correction” formula for evaluation of mixing studies. Am J Clin Pathol 2002; 117 (1) 62-73
• 9 Devreese KM. Interpretation of normal plasma mixing studies in the laboratory diagnosis of lupus anticoagulants. Thromb Res 2007; 119 (3) 369-376
• 10 Moore GW, Savidge GF. The dilution effect of equal volume mixing studies compromises confirmation of inhibition by lupus anticoagulants even when mixture specific reference ranges are applied. Thromb Res 2006; 118 (4) 523-528
• 11 Moore GW, Henley A, Greenwood CK, Rangarajan S. Further evidence of false negative screening for lupus anticoagulants. Thromb Res 2008; 121 (4) 477-484
• 12 Thom J, Ivey L, Eikelboom J. Normal plasma mixing studies in the laboratory diagnosis of lupus anticoagulant. J Thromb Haemost 2003; 1 (12) 2689-2691
• 13 Kaczor DA, Bickford NN, Triplett DA. Evaluation of different mixing study reagents and dilution effect in lupus anticoagulant testing. Am J Clin Pathol 1991; 95 (3) 408-411
• 14 Devreese KM. No more mixing tests required for integrated assay systems in the laboratory diagnosis of lupus anticoagulants?. J Thromb Haemost 2010; 8 (5) 1120-1122
• 15 Favaloro EJ, Bonar R, Zebeljan D, Kershaw G, Marsden K. Laboratory investigation of lupus anticoagulants: mixing studies are sometimes required. J Thromb Haemost 2010; 8 (12) 2828-2831
• 16 Bonar R, Favaloro EJ, Zebeljan D , et al. Evaluating laboratory approaches to the identification of lupus anticoagulants: a diagnostic challenge from the RCPA Haematology QAP. Pathology 2012; 44 (3) 240-247
• 17 Chantarangkul V, Tripodi A, Arbini A, Mannucci PM. Silica clotting time (SCT) as a screening and confirmatory test for detection of the lupus anticoagulants. Thromb Res 1992; 67 (4) 355-365
• 18 Triplett DA, Barna LK, Unger GA. A hexagonal (II) phase phospholipid neutralization assay for lupus anticoagulant identification. Thromb Haemost 1993; 70 (5) 787-793
• 19 Loeliger A. Prothrombin as cofactor of circulating anticoagulant in systemic lupus crythematosus. Thromb Diath Haemorrh 1959; 3: 237-256
• 20 Schleider MA, Nachman RL, Jaffe EA, Coleman M. A clinical study of the lupus anticoagulant. Blood 1976; 48 (4) 499-509
• 21 Yin ET, Gaston LW. Purification and kinetic studies on a circulating anticoagulant in a suspected case of lupus erythematosus. Thromb Diath Haemorrh 1965; 14 (1–2) 88-115
• 22 Oosting JD, Derksen RH, Entjes HT, Bouma BN, de Groot PG. Lupus anticoagulant activity is frequently dependent on the presence of beta 2-glycoprotein I. Thromb Haemost 1992; 67 (5) 499-502