If a2GPI antibodies are unfavorable, then aCL antibodies recognize other binding proteins different from 2GPI whose clinical significance is unknown [47]. and may be useful in risk stratification of APS patients. Because of the methodological shortcomings of immunological and clotting assays, these non-criteria aPL may be useful in patients with incomplete antibody profiles to confirm or exclude the increased risk profile. This manuscript will focus on the laboratory aspects, the clinical relevance of assays and interpretation of aPL results in the diagnosis of APS. Keywords:Antiphospholipid syndrome, Anticardiolipin antibodies, Anti-2 glycoprotein I antibodies, Lupus anticoagulant, Non-criteria antiphospholipid antibodies == Highlights == The presence of antiphospholipid antibodies (aPL) define the diagnosis of the antiphospholipid syndrome (APS). Laboratory criteria are lupus anticoagulant, anticardiolipin (aCL), and antibeta2-glycoprotein I antibodies (a2GPI) IgG/IgM. Lupus anticoagulant measurement, as well as solid phase assays for aCL and IFN alpha-IFNAR-IN-1 hydrochloride a2GPI, show methodological difficulties. Antibodies against domain name I of 2GPI (aDI) and antiphosphatidylserine-prothrombin (aPS/PT) antibodies are non-criteria aPL. aDI and aPS/PT may be useful in risk stratification of APS patients. == 1. Introduction == The antiphospholipid syndrome (APS) is an auto-immune disease defined by the clinical presentation of thromboembolic complications and/or pregnancy morbidity. The classification criteria for APS include, besides the clinical criteria, the presence of persistently positive antiphospholipid antibodies (aPL). The clinical and laboratory diagnosis of APS is usually challenging, and has preoccupied haematologists, rheumatologists, obstetricians and pathologists since its first description in 1983 until today. Even though Sydney criteria were designed as classification criteria, the laboratory parameters are used as diagnostic criteria. It took many years to further define these diagnostic laboratory criteria that are still prone to conversation and need for regular updates. The laboratory diagnosis IFN alpha-IFNAR-IN-1 hydrochloride of APS relies on the detection of IFN alpha-IFNAR-IN-1 hydrochloride aPL. APL are a heterogeneous group of autoantibodies, but in the current classification criteria only lupus anticoagulant (LA), anticardiolipin (aCL) and antibeta2-glycoprotein I antibodies (a2GPI) IgG or IgM are defined as laboratory criteria, if persistently present [1,2]. The confirmation of a positive result after twelve weeks was added to the classification criteria to avoid overdiagnosis, and to exclude patients with transient aPL to be regarded as APS. Clinical criteria of APS, thrombotic events as well as pregnancy morbidity, are common Sstr3 in the general population, and often not caused by aPL presence, causing a great need for reliable aPL assays [3]. Moreover, laboratory criteria are very important since the type and level of aPL determine the risk in APS patients [[4],[5],[6],[7]]. A huge number of publications on which laboratory tests to use have been published during the past years, sometimes with conflicting information. The current classification criteria limit the laboratory parameters to three groups of aPL: LA, aCL and a2GPI IgG and IgM. However, optimization of laboratory diagnosis and risk stratification opens the field towards so-called non-criteria aPL. Antiphosphatidylserine-prothrombin (aPS/PT) antibodies gain importance during the last 12 months based on clinical studies illustrating their role in thrombotic events as well as pregnancy complications [8]. Other aPL such as antibodies against the domain name I of beta2-glycoprotein (aDI) are pathogenic and confirm the risk for clinical APS related manifestations [[9],[10],[11],[12]]. == 2. Patient selection for screening for antiphospholipid antibodies == Screening for aPL in the context of APS, should focus on patients with a high probability of having APS. Indiscriminate screening is usually strongly discouraged to avoid incidental findings [13,14]. Patient selection is usually summarized inTable 1. == Table 1. == Patient selection for antiphospholipid antibody screening in patients likely to have APS [13,14,19,84]. == 3. Lupus anticoagulant == LA measurement detects all aPL binding to phospholipid of cell membranes, independent of the phospholipid binding protein that acts as ligand for aPL. Consequently, LA are a heterogeneous group of aPL. Amongst all antibody aPL cofactors, 2glycoprotein I and prothrombin have the most significant association with pathogenicity [15]. LA represents an intriguing paradox [16,17]. This class of aPL causes a phospholipid-dependent prolongation of the clotting time but is associated with an increased risk of thrombosis and pregnancy morbidity. The methodology explained in the 1990’s has essentially not changed and uses on a multistep process [14,[18],[19],[20]]. As laboratory test, LA is challenging. IFN alpha-IFNAR-IN-1 hydrochloride The analysis of LA is usually complex, with many pitfalls in the preanalytical conditions, applied process, and interpretation [21,22]. Guidelines for LA detection has been proven to benefit harmonization of methods [19,23,24]. A comparative study on analyzing samples showed that good agreement in LA overall performance between laboratories can be achieved by using the same test protocols and test systems [25]. A survey on methodology of LA initiated by the International Society on Thrombosis and Haemostasis Scientific and Standardization Subcommittee on LA/aPL (ISTH-SSC) showed that there was good agreement on sample preparation, choice of assays, repeat testing, and the use of in interpretative feedback. However, on other issues, such as testing IFN alpha-IFNAR-IN-1 hydrochloride in patients on anticoagulation, cutoff values, and calculation and interpretation of results, there.
