Rationale.

Several autoantibodies have been proposed for the differential diagnosis of Systemic Lupus Erythematosus (SLE). Use of these autoantibodies might result in different operational characteristics.

Objective.

To assess the operational characteristics of selected autoantibodies in the differential diagnosis of SLE.

Study design.

Retrospective, analytical.

Study serie.

One-hundred and sixty-nine subjects (SLE: 35.5 %; Non-SLE diseases of connective tissue: 38.5 %; Apparently healthy subjects: 26.0 %; Women: 84.6 %; Average age: 30.9 ± 17.9 years; Average evolution time of lupic disease: 3.9 ± 4.7 years).

Methods.

Anti-double stranded DNA (anti-dsDNAdc), anti-nucleosomes (anti-Nuc), anti-Smith protein (anti-Sm) and anti-ribosomes (anti-Rib) autoantibodies were determined by immunoenzymatic techniques (Orgentec Diagnostika, Mainz, Alemania). Anti-nuclear antibodies (ANA) were indistinctely determined either by immunoenzimatic techniques (ANA-EIA) or immunofluorescent methods with Hep2 cells (ANAHep2). Operational characteristics of the autoantibodies in the differential diagnosis of SLE were calculated. In addition, corresponding ROC curves for each instance of analysis were obtained, and diagnostic accuracy was estimated from the area under the ROC curve (AROC).

Results.

Accuracy of the autoantibodies used in the differential diagnosis of SLE was as follows (in descending order): anti-dsDNA: 0.9528 ± 0.0288; anti-Nuc: 0.7851 ± 0.0675; ANA-EIA: 0.7755 ± 0.2633; anti-Sm: 0.5926 ± 0.0790; anti-Rib: 0.5770 ± 0.2641; and ANA-Hep2: 0.5341 ± 0.2635; respectively. With the exception of anti-dcDNA, operational characteristics of the remaining antibodies were dependent upon cut-off value, sampled subpopulation, and analytical method.

Conclusions.

anti-dsDNA antibodies were the most accurate in the differential diagnosis of SLE.

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