ABSTRACT
OBJECTIVES: To compare the utility of indirect immunofluorescence for the detection of antinuclear antibodies (ANA-IIF) and a fully automated test (ELiA Symphony) that detects antibodies against a mixture of nuclear and cytoplasmic antigens (ENA), to select sera that should be tested for non-antidouble-stranded DNA (dsDNA) antinuclear antibodies in a relatively expensive automated line immunoassay (INNO-LIA ANA update, Lineblot). METHODS: All 328 sera sent to the laboratory for ANA or anti-ENA tests, over a 4 month period were evaluated in all three assays. Results were related to signs and symptoms of systemic autoimmune disease (AID) that patients had before or at the time of blood sampling. RESULTS: Overall, 72 (22%) sera were Lineblot positive. Of 198 patients without clinical manifestations of AID, 7% were Lineblot positive. Limiting Lineblot to sera positive in either ANA-IIF or Symphony tests failed to detect 26 (ANA-IIF) and 22 (Symphony) Lineblot-reactive sera, with 15 sera being negative in both assays. From a clinical point of view, failure to detect these reactivities was not important in most cases. CONCLUSIONS: Restriction of performance of Lineblot to patients with at least one criterion for AID is an ideal and cost-effective strategy. In ignorance of clinical signs and symptoms, screening of sera by ANA-IIF or Symphony strongly reduces the costs of anti-ENA detection, with minimal loss in diagnostic capacity. Based on small differences, including the fact that anti-dsDNA antibodies give a positive ANA-IIF, we prefer screening with ANA-IIF over Symphony.
Subject(s)
Antibodies, Antinuclear/blood , Autoimmune Diseases/diagnosis , Adolescent , Adult , Aged , Aged, 80 and over , Biomarkers/blood , Child , Child, Preschool , Cost-Benefit Analysis , DNA/immunology , Fluorescent Antibody Technique, Indirect/economics , Fluorescent Antibody Technique, Indirect/methods , Health Care Costs/statistics & numerical data , Humans , Immunoassay/economics , Immunoassay/methods , Infant , Middle Aged , Netherlands , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
OBJECTIVE: To compare test characteristics of the Farr radioimmunoassay and an automated fluorescence immunoassay (ELIA dsDNA test) for the diagnosis of systemic lupus erythematosus (SLE). METHODS: A cross sectional study comprising 440 samples from 440 patients, sent to the laboratory over a three month period for anti-dsDNA testing. Chart review was performed, blinded for test results, to count for each patient the number of American College of Rheumatology criteria for the classification of SLE that were fulfilled. At least four criteria were met by 248 (56%) patients (SLE), one to three criteria by 77 (18%) (lupus-like disease, LLD), and no criterion by 115 (26%) (non-SLE/non-LLD). Results from serum samples from the non-SLE/non-LLD and SLE groups were used to calculate receiver operating characteristic curves. RESULTS: For the Farr assay, specificities of 95% and 99% corresponded to sensitivities of 72% and 56% respectively. For the ELIA dsDNA test these levels of specificity corresponded to sensitivities of 44% and 17% respectively. CONCLUSIONS: The Farr radioimmunoassay is superior to the ELIA dsDNA test for identifying patients with SLE.
