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Simultaneous Distinction of Monospecific and Mixed DFS70 Patterns During ANA Screening with a Novel HEp-2 ELITE/DFS70 Knockout Substrate
Published on: January 17, 2018
Evaluation of Anti-dsDNA Antibodies in Laboratory Practice: Management of Different Analytical Methods and
Massimo Papale1, Carmela Paolillo2, Loredana Iafelice1
1Laboratory of Clinical Pathology, Department of Laboratory Diagnostics, Polyclinic University-Hospital Foggia, 71122 Foggia, Italy.
Background:
Anti-double-stranded DNA (anti-dsDNA) antibodies are a key serological marker for systemic lupus erythematosus (SLE) and are commonly assessed in conjunction with anti-nuclear antibody (ANA) testing by indirect immunofluorescence (IIF) on HEp-2 cells. However, their detection is influenced both by the heterogeneity of the autoimmune response and by the characteristics of the analytical method employed, thereby complicating diagnostic interpretation.
Methods:
In this retrospective single-center study, 3090 consecutive patients undergoing anti-dsDNA analysis were screened, and 138 positive individuals, with anti-dsDNA levels ≥ 15 IU/mL by fluoroenzyme immunoassay (FEIA), were included in the study. A control group of 29 anti-dsDNA-negative patients was also analyzed. Anti-dsDNA-positive patients were stratified by antibody level (low, mild, high), and the results were correlated with HEp-2 IIF titers and fluorescence patterns. Furthermore, in a subset of 30 positive patients, anti-dsDNA antibodies were evaluated using immunoblotting (IB) and the Crithidia luciliae indirect immunofluorescence test (CLIFT). Statistical analyses assessed associations and concordance among methods.
Results:
Higher anti-dsDNA levels were generally associated with higher HEp-2 IIF titers. However, a considerable percentage (35%) of patients with positive anti-dsDNA were negative by HEp-2 IIF. Notably, high anti-dsDNA levels were detected in 19% of HEp-2 IIF-negative patients (titer < 1:80), 18% of mildly HEp-2 IIF-positive patients (titer 1:80-1:160), and 25% of HEp-2 IIF-positive patients (titer > 1:320). In the subset of 30 positive patients, FEIA analysis showed high concordance with the immunoblot in both IIF-positive (81%) and -negative (100%) patients, while CLIFT demonstrated lower agreement with both FEIA and IB independently of the IIF.
Conclusions:
Our findings indicate that anti-dsDNA antibody detection may occur independently of HEp-2 IIF positivity and that FEIA, especially when confirmed by immunoblot, represents a reliable approach for anti-dsDNA assessment. The observed results in this study likely reflect differences in epitope recognition and assay sensitivity among methods, suggesting the use of a multi-step diagnostic strategy in the serological evaluation of SLE.
