The use of laboratory tests in diagnosis and monitoring of systemic lupus erythematosus.

Clinical immunology laboratories play an essential role in diagnosis and monitoring of systemic lupus erythematosus (SLE). To obtain the best results in terms of diagnostic performance and clinical usefulness, the following recommendations should be fulfilled: Indirect immunofluorescence on Hep-2 cells remains the method of choice for the detection of anti-nuclear antibodies (ANA). The sensitivity of ANA test for SLE is very high (almost 100%) but its specificity low since ANA can be present in a number of different clinical conditions and even in normal controls. Anti-dsDNA antibodies are highly specific for SLE and present in a high proportion of SLE patients (40-80%). The method of choice for anti-ds DNA is the Farr assay; however, the necessity of using radioactive material decreases its applicability. As an alternative, immunofluorescence on Crithidia Luciliae can be used in the diagnostic phase for its high specificity. It is not advisable to use ELISA, in the diagnostic phase, due to its low specificity. The quantitative determination of anti-dsDNA is useful for monitoring patients, in particular in the presence of nephritis. For monitoring, a quantitative method should be used (Farr assay or ELISA). The detection of antibodies to extractable nuclear antigens (ENA) and to phospholipids (Lupus anticoagulant and anti-cardiolipin antibodies with a beta2 glycoprotein I-dependent method) are useful to identify subgroups of patients at risk for some clinical manifestations (i.e. anti-phospholipid syndrome). New assays (anti-C1q and anti-nucleosome antibodies) have been recently proposed for diagnosis (anti-nucleosome) and monitoring SLE patients (anti-C1q and anti-nucleosome antibodies), with promising results. Among biological parameters, urinary levels of monocyte chemoattranct protein 1 (MCP1) seem to be the most useful to monitor nephritis activity in lupus patients.