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Year : 2011  |  Volume : 2  |  Issue : 1  |  Page : 25-33

Evaluation of the Laboratory tests used in the Identification of Lupus Anticoagulants

1 Coagulation Research Laboratory, Department of Physiology College of Medicine and King Khalid University Hospital Riyadh, Saudi Arabia King Saud University
2 Department of Pathology, Faculty of Medicine, University of Khartoum, Sudan

Correspondence Address:
Abdel Galil M Abel Gader
The Coagulation Research Laboratory Department of Physiology College of Medicine and King Khalid University Hospital King Saud University Riyadh 11461, Saudi Arabia

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Source of Support: None, Conflict of Interest: None

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Background: Lupus anticoagulant (LA) refers to a group of autoantibodies that inhibit certain phospholipid-dependent coagulation reactions, and typically cause prolongation of activated partial thromboplastin time (APTT). These are diverse laboratory tests for antiphospholipid antibodies (APAs). This situation is compounded further by the lack of ΢ a golden standardΣ for their detection and this has resulted in wide variation in LA testing between laboratories. The aim of this study is to evaluate the sensitivity of a wide range of assay procedures and reagents in common use for the detection of LA in patients with recurrent fetal loss. Patients: Citrated blood samples were collected from 110 women with recurrent fetal loss (RFL) attending a special outpatient RFL Clinic, King Khalid University Hospital, Riyadh. They had history of 3 or more consecutive spontaneous unexplained abortions before the 10th week of gestation. Their ages ranged from 20 to 43 years (mean=30΁7.5). Control group: 110 normal healthy Blood Donors. Blood Sample Processing: Citrated blood samples were subjected to double 15 min centrifugation at 3000 rpm. The resulting platelet poor plasma (PPP) was either tested immediately or stored in aliquots in the frozen state at -40ͱC for testing later. Results of laboratory Tests Used For Detection La: the detection rates for LA among RFL patients versus healthy controls are as follows: * The activated partial thromboplastin time (APTT, Manchester Reagent) (17.3% vs. 3.6%) Mixing studies either with normal plasma (NP) or the platelet neutralization procedure (PNP): * Prolonged APTT + NP: (11% vs. 2.7%); * Prolonged APTT + PNP: (6.3% vs. 1.8%) * The Staclot-LA test kit (Diagnostica Stago, France) (25.5% vs. 6.3%); * PTT-LA (Diagnostica Stago, France): (4.5% vs 4.5%); * The Kaolin Clotting Time (KCT) (28.1% vs. 1.8%); * The Dilute RussellΥs Viper Venom Test (dRVVT), (35.5% vs. 6.3%). Conclusions: The dRVVT followed by the KCT identified more patients with LAC among those with RFL, than the other tests, particularly the lowphosopholipid APTT (Manchester Reagent). Staclot LA is a complete system of confirmatory and screening tests. Staclot LA is easy to perform and commercially available as a complete test system, containing both testing and confirming for LA. PTT-LA is least sensitive for the detection of LAC. The other more feasible confirmatory test is PNP combined with a sensitive APTT reagent. Depending on the available financial resources, laboratories may follow different practices in diagnosing LAC ranging from one test to combinations test procedures.

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