EnzymeimmunoassayforthequantitativedeterminationofRheumatoidfactor(RF)IgAinhumanserumorplasma.
Patientssufferingfromrheumatoidarthritis(RA)exhibitRFautoantibodiesrecognizingtheFcpartofIgG.RAorchronicpolyarthritishasayetunknownetiologyandrepresentsthemost
frequentrheumaticinflammatorydisorderdemonstratingaprevalenceofupto1%.OneofthetypicalmanifestationsofRAissymmetricsynovialitisoflimbjointsoftenaccompaniedbyinvolvementofthecervicalspinalcolumn.BesideclinicalfeaturesoneofthecriteriaoftheAmericanCollegeofRheumatologyfortheclassificationofRAisthepresenceofRF.Upto80%ofRApatientsmaydemonstrateRF.RFcanoccuryearspriortotheonsetofdiseaseandRFpositiveapparentlyhealthyindividualsbeara5-40timeshigherrisktodevelopRA.However,patientssufferingfromotherautoimmune,infectiousorB-celllymphoproliferative
disordersaswellasapparentlyhealthyelderlyindividualsmaydevelopRF.HighconcentrationsofRFareoftenassociatedwithamoreseverediseasecomprisingafasterdestructionofjoints.Inadditiontheyarefoundinpatientswithextra-articularmanifestationssuchasrheumatoidnodules,polyneuropathy,vasculitisorSiccasyndrome.RFmaybelongtotheIgG,IgMorIgAisotypewhereasIgMRFisthemostfrequentisotypetobedeterminedinRApatients.Extra-articularmanifestationsseemtobeassociatedwithIgARF.LikeRFoftheIgMisotypehighconcentrationsofIgGRFseemstoappearwithpatientssufferingfrommoreprogressiveerosionsofjoints.Inlong-timeRAIgAandIgGRFareconsideredtobeprognosticMarkersforsystemicmanifestation.