Session Title: Systemic Lupus Erythematosus: Clinical Aspects
Session Type: Abstract Submissions (ACR)
Background/Purpose: In systemic lupus erythematosus (SLE), antibodies to double-stranded DNA (dsDNA) are utilized for disease classification and assessment of activity. Enzyme immunoassays (EIAs) and multiplex immunoassays (MIAs) are frequently used. However, anti-dsDNA antibody assays are not well-standardized with previously reported low concordance rates. In this study, clinical factors and laboratory data were evaluated for their association with anti-dsDNA antibody testing performed by EIA and MIA.
Methods: Patients from a single institution (n=102) underwent anti-dsDNA antibody testing by EIA (INOVA Diagnostics) and MIA (BioRad Laboratories). Clinical diagnoses, SLE disease activity index (SLEDAI), medication exposure, and laboratory data (serologies, complement values, and inflammatory markers) were abstracted. Qualitative concordance between the two methods was defined as both methods being classified as “negative” or “positive” according to the manufacturer’s recommended reference ranges. Discordance was defined as one method having different categorization than the other, “positive,” “borderline/indeterminate,” or “negative.”
Results: Within the total cohort, 35% and 44% of patients were positive for anti-dsDNA antibodies by EIA and MIA, respectively. Further, 54 had a diagnosis of definite, probable, or cutaneous SLE with 63% positive by MIA and 50% by EIA. In addition, only 6% of these patients had negative concordance, while 37% demonstrated positive concordance (p=0.02). Of those negative by both methods, none had lupus nephritis. In patients with lupus nephritis, 35% demonstrated positive concordance. The remaining demonstrated discordance with a higher qualitative value of MIA in 52% compared to 13% with EIA higher (p=0.14). The mean SLEDAI score calculated without the anti-dsDNA value was 3.3 in patients with negative concordance and 7.7 with positive concordance. In comparison, patients with discordant higher MIA had a mean SLEDAI score of 5.9 compared to 2.9 in patients with higher EIA (p=0.1). No patients with negative concordance had low complement values. In contrast, in patients who were positive by both methods, a low C3 or C4 was observed in 46% (p<0.01) and 62% (p=0.01), respectively. Of patients with positive concordance, 53% were positive for anti-SS-A antibodies and anti-RNP antibodies compared to 8% and 23% of patients with negative concordance, respectively. In patients with positive MIA, 80% were currently on at least one medication for SLE, compared to 37% with negative and 39% with borderline MIA results (p<0.01). In patients with positive MIA, they were more likely to have been treated with cyclophosphamide and hydroxychloroquine. In contrast, 73% of patients with positive EIA were currently on at least one medication for SLE compared to 43% and 63% of patients with negative or borderline results (p=0.09).
Conclusion: The association between clinical factors and anti-dsDNA antibodies may be determined, in part, by the specific methodology. Further clarification of these relationships could assist with interpretation of anti-dsDNA antibody results as well as choice of a method for a specific clinical scenario.
M. L. Krause,
M. R. Snyder,
Inova Diagnostics, Inc.,
C. S. Crowson,
A. B. Green,
K. G. Moder,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-correlation-with-anti-double-stranded-deoxyribonucleic-acid-via-enzyme-linked-immunoassay-versus-multiplex-immunoassay/