The clinical usefulness of commonly used autoantibody assays in SLE
| Test (EQA scheme?) | Technique | Diagnostic specificity | Clinical usefulness | Use in monitoring activity | Evidence base |
|---|---|---|---|---|---|
| EQA +, UK external quality assessment scheme available. | |||||
| ACA, anticardiolipin antibody; ANA, antinuclear antigen; β2GP1, β2 glycoprotein 1; CIE, countercurrent immunoelectrophoresis; CRP, C reactive protein; dsDNA, double stranded DNA; ELISA, enzyme linked immunosorbent assay; ENA, extractable nuclear antigen; IB, immunoblotting; ID, immunodifussion; IIF, immunofluorescence; RNP, ribonuclear protein. | |||||
| ANA (EQA+) | IIF rodent tissue | Moderate for homogenous or speckled pattern at ≥1/160 in selected patients, IgG only | Initial screen for further testing | Poor (semiquantitative) | Extensive |
| IIF HEp-2 | Moderate for homogenous or speckled pattern at ≥1/160 in selected patients, IgG only | Initial screen for further testing | Poor (semiquantitative) | Extensive | |
| IIF ELISA | Unknown | Unknown | Possible | Limited | |
| dsDNA (EQA+) | Farr | Good, known causes of false positives | Good for diagnosis and monitoring | Useful in subset of patients | Extensive |
| Crithidia IIF | Good, known causes of false positives | Good for diagnosis | Poor (semiquantitative) | Extensive | |
| ELISA | Variable, assay dependent, IgG specific good, known causes of false positives | Assay dependent, good for IgG specific | Assay dependent, good for IgG specific | Moderate | |
| Nitrocellulose | Moderate | Moderate | No | Limited | |
| Complement C3, C4 (EQA+) | Nephelometry/ turbidometry | None | Moderate, low C3 in renal disease | Useful in subset of SLE, serial values essential | Extensive |
| CRP (EQA+) | Nephelometry/ turbidometry | None | CRP usually low in active SLE except in severe serositis | Useful to distingiush infection from SLE activity | Moderate |
| ENA Ro/La/ Sm/RNP (EQA+) | Immunodiffusion/CIE | Good for Sm, moderate for Ro/La, may be poor for RNP | Good for defining ANA specificity | No, except where disease has evolved new features | Extensive |
| IB | Good, but may be insensitive for Ro | Good | No | Moderate | |
| ELISA | As ID/CIE but more sensitive for Ro/RNP, less specific if low titre or IgM positive | Good for IgG antibody at appropriate cut off | No, except where disease has evolved new features | Extensive | |
| Haemagglutination | Poor, less specific, detects IgM | Poor | No, semiquantitative | Limited | |
| Antiphospholipid antibodies (ACA EQA+) | ACA ELISA | Poor, even for IgG antibodies | Moderate, especially IgG specific | Possible | Extensive |
| Anti-β2GP1 ELISA | Moderate for IgG antibodies | Moderate, especially IgG specific | Unknown | Moderate | |
| Lupus anticoagulant | Poor | Moderate | Unknown | Moderate | |
| Antihistone antibodies | ELISA | Poor, even for drug induced SLE | Poor | Possible | Limited |
| IB | Poor, even for drug induced SLE | Poor | No | Limited | |