Laboratory screening of connective tissue diseases by a new automated ENA screening assay (EliA Symphony) in clinically defined patients.
BACKGROUND
The measurement of antinuclear antibodies (ANA) is used in the autoimmune laboratory for the screening of connective tissue diseases (CTD). ANA measurements are mainly performed by indirect immunofluorescence (IIF) on HEp-2 cells or by enzyme immunoassay (EIA). The objective of this study was to clinically evaluate an automated EIA for extractable nuclear antigens (ENA) which lacks anti-dsDNA for the screening of CTD.


METHODS
The study involved a total of 170 serum samples, 54 from patients with CTD, 26 from patients with other autoimmune diseases, and 90 from patients with non-autoimmune diseases. For all sera, ANA detection was performed by IIF and by EliA Symphony (Pharmacia Diagnostics, Freiburg, Germany), an ENA screening which detects the following autoantibodies: SSA/Ro, SSB/La, U1RNP (70 kDa, A, C), Scl-70, JO-1, centromere B and Sm. Also, anti-dsDNA (EliA dsDNA, Pharmacia Diagnostics, Freiburg, Germany) was measured on all samples. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), efficiency, positive likelihood ratio (PLR), and negative likelihood ratio (NLR) were calculated.


RESULTS
Diagnostic efficiency was similar for IIF (82.6%) and EliA Symphony (82.3%), as well as PLR (6.5 for IIF, and 7.3 for Eli Symphony), and NLR (0.35 for IIF, and 0.41 for EliA Symphony). The combined measurement of EliA Symphony and dsDNA increased sensitivity but not PLR. Area under receiver operator characteristic (ROC) curve was similar for IIF (0.847) and EliA Symphony (0.823).


CONCLUSIONS
The results of the study demonstrate that EliA Symphony solely or combined with anti-dsDNA detection has an efficiency similar to HEp-2 cells IIF with a cut-off of 1:160 for the diagnosis of CTD.
González
Concepción
C
Laboratorio de Autoinmunidad, Servicio de Bioquímica, Hospital Universitario, 37007 Salamanca, Spain.
García-Berrocal
Belén
B
Pérez
Marta
M
Navajo
José A
JA
Herraez
Oscar
O
González-Buitrago
José M
JM
D000974:Antibodies, Antinuclear / Q000032:analysis*; D003240:Connective Tissue Diseases / Q000175:diagnosis* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D012372:ROC Curve; D012680:Sensitivity and Specificity
D000974:Antibodies, Antinuclear