Serin-ProthrombinIgG/IgMELISAisasolidphaseenzymeimmunoassaywithhighlypurifiedphosphatidyl-serineplusnativehumanprothrombinforthecombinedquantitativedetectionofIgGand/orIgMantibodiesagainstphosphatidyl-serineandprothrombininhumanserum.Theassayisanaidinthediagnosisandriskestimationofthrombosisinpatientswithsystemiclupuserythematosusandanti-phospholipidsyndrome(APS).Antibodiesagainstprothrombinandphosphatidyl-serine,anacidicphospholipidderivedfromglycerol,belongtothegroupofanti-phospholipidantibodiesspecificforphospholipidssuchascardiolipin,phosphatidyl-inositol,-ethanolamin,-choline,sphingomyelin,phosphatidicacidandprothrombin.PhospholipidsarecomponentsofBIOLOGicalmembranes.Prothrombin(humanfactorII)isaplasmezymogenwithamolecularweightof72kDa.ItassembleswiththeactivatedformsofFactorV,FactorXandphospholipidtoformacatalyticunitknownastheprothrombinasecomplex.Inthepresenceofcalciumions,thecomplexcleavesthemembrane-associatedprothrombinintothrombin,whichisthenreleasedintothesolublephase.Anti-phospholipidantibodiesarefrequentlyfoundinseraofpatientswithsystemiclupuserythematosus(SLE)andrelateddiseases.Theoccurrenceofanti-phospholipidantibodiesinpatientswithSLEandrelateddiseasesistypicalforasecondaryanti-phospholipidsyndrome(APS).Incontrast,antiphospholipidantibodiesinpatientswithnootherautoimmunediseasescharacterizetheprimaryAPS.Manystudieshaveshownacorrelationbetweentheseautoantibodiesandanenhancedincidenceofthrombosis,thrombocytopeniaandhABItualabortions(asaconsequenceofplacentalinfarction).Theexactmechanismsbywhichpathogenicanti-phospholipidantibodiesinducethrombosisisnotyetrevealedfully.AntibodiestargetingprothrombinalonehaverecentlybeendescribedbeinghighlyassociatedwithfetallossinAPSpatients.ProthrombinantibodiesarethefirstMarkerforthisseriouscomplicationasallotherknownantiphospholipidantibodiesfailedtocorrelatewithfetalloss.Additionally,antibodiestargetingacomplexofprothrombinandphosphatidylserinehavebeenassociatedwiththesecondmajorgroupofclinicalmanifestationsoftheAPS,venousandarterialthrombosis.However,theyfailedtoshowanycorrelationwithfetalloss.Therefore,bothtypesofantibodiesserveasanimportantdiagnostictoolfordifferentialdiagnosisoftheheterogenousmanifestationsoftheAPS.