New methods for antinuclear antibody testing: does it cut costs and corners without jeopardizing clinical reliability?

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Abstract

BACKGROUND

Antinuclear antibodies (ANAs) are detected in the serum of patients with most systemic autoimmune diseases. The traditional tool used to detect ANAs is indirect immunofluorescence. A new, automated test, the ELiA Symphony, detects antibodies against a mixture of nuclear and cytoplasmic antigens (ENAs), in order to select sera samples that should be further tested using a more expensive, automated line immunoassay, the Lineblot test, to test for ANAs to non-antidouble-stranded-DNA.

OBJECTIVE

The object of this study was to compare the cost and efficacy of indirect immunofluorescence for the detection of ANAs with a fully automated test, the ELiA Symphony, in order to diagnose autoimmune disease.

DESIGN AND INTERVENTION

This study included sera samples from patients that were sent to the laboratory of Immunology at the University Hospital Utrecht to be tested for the presence of ANAs or anti-ENAs. Over a 4-month period, sera samples were evaluated using indirect immunofluorescence, the ELiA Symphony test and the Lineblot test. Sera testing positive for ANAs using indirect immunofluorescence were then tested for antidouble-stranded DNA antibodies, using the Farr assay. Results were compared to the incidence of signs and symptoms of systemic autoimmune disease, which was determined both before and after samples were taken.

OUTCOME MEASURES

The primary outcome measure of this trial was the comparative accuracy and cost-effective ness of indirect immunofluorescence, the ELiA Symphony test and the Lineblot test in detecting ANAs related to systemic auto immune disease.

RESULTS

In total, 328 sera samples were analyzed, of which 72 (22%) of samples were Lineblot positive. Of the 198 patients who did not have clinical indications of systemic autoimmune disease, 7% were Lineblot positive. When the Lineblot test was used to analyze only indirect-immunofluorescence-positive and ELiA-Symphony-positive samples, Lineblot-positive sera were not detected in either case (26 samples from the indirect-immunofluorescence group and 22 samples from the ELiA-Symphony group); a total of 15 samples were detected as negative for ANAs. This failure to detect reactivity was classified as clinically unimportant by the authors.

CONCLUSION

The authors conclude that patients who meet at least one criterion for systemic autoimmune disease can be restricted to the Lineblot test; this is both an efficacious and cost-effective strategy. Screening sera samples using indirect immunofluorescence or the ELiA Symphony test, when clinical symptoms of disease have not been observed, will strongly reduce the costs of anti-ENA detection. In this case, it is preferable to screen patients with indirect immunofluoresence, rather than the ELiA Symphony test.

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