Table 2

Common attributes of individual assay technologies used for the diagnosis and monitoring of SLE (all assays produce some false positive results)

AssayProblemsAdvantagesResult
ELISA, enzyme linked immunosorbent assay; IIF, immunofluorescence.
IIF rodent tissueSubjective, Ro may be missed, semiquantitative, pattern not diagnostic, cannot detect cell cycle related patterns, not specificCheap, can be isotype specificSemiquantitative end point titration or qualitative result at screening titre + pattern
IIF HEp-2Subjective, Ro may be missed, semiquantitative (poor precision), pattern not diagnostic, not specificCheap, recombinant Ro60 expression to boost Ro sensitivity available, can be isotype specificSemiquantitative end point titration or qualitative result at screening titre + pattern
Ouchterlony double diffusion (ID)Slow, crude antigens, subjective, qualitative, requires experience, not isotype specific, some false negativesSpecific, cheapPositive or negative + antigen specificity
Countercurrent immunoelectrophoresis (CIE)Slow, crude antigens, semiquantitative, requires experience, not isotype specific, some false negativesAs ID, but more sensitivePositive or negative + antigen specificity
HaemagglutinationDetects IgG and IgM, semiquantitative, subjective, detects low affinity antibodiesCheapPositive or negative + semiquantitative titre
Immunoblotting (IB)Qualitative, may be insensitive for Ro, crude antigen, labour intensiveSensitive, very specific for individual antigensPositive or negative + antigen specificity
Immunoprecipitation (Farr)Radioactive, labour intensive, expensive, technically difficult, no isotype specificity, false positivityQuantitative, high specificity, detects high affinity antibodiesQuantitative result, potentially in standardised IU/l if reference preparation available
ELISADetects low affinity antibodies, needs high purity well defined antigens (native v recombinant), false positivitySensitive, variable, can be polyspecific or IgG specificQualitative or quantitative results, potentially in standardised IU/l if reference preparation available