ACR Meeting Abstracts

ACR Meeting Abstracts

Abstract Number: 704

Detection of dsDNA Antibodies By New Fluoroimmunoassay with Comparable Diagnostic Sensitivity and Specificity to Farr-Ria

Katja Lakota1,2, Tanja Kveder2, Tinka Svec2, Polona Žigon2, Ales Ambrozic3, Borut Božič2,4, Matija Tomšič2,5, Saša Čučnik2,4 and Snezna Sodin Semrl1,2, 1Faculty of Mathematics, Natural Science and Information Technology, University of Primorska, Koper, Slovenia, 2Department of Rheumatology, University Medical Centre Ljubljana, Ljubljana, Slovenia, 3Department of Rheumatology, University Medical Centre Ljubljana, 1000 Ljubljana, Slovenia, 4Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia, 5University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia

Meeting: 2017 ACR/ARHP Annual Meeting

Date of first publication: September 18, 2017

Keywords:

Session Information

Date: Sunday, November 5, 2017

Title: Systemic Lupus Erythematosus – Clinical Aspects and Treatment Poster I: Biomarkers and Outcomes

Session Type: ACR Poster Session A

Session Time: 9:00AM-11:00AM

Background/Purpose:

Antibodies against double-stranded deoxyribonucleic acid (anti-dsDNA) are a useful and valuable serological marker for diagnosis of systemic lupus erythematosus (SLE). Studies suggest strong correlation between increasing levels of anti-dsDNA and subsequent flares, particularly renal disease. The radioactive immunoassay (RIA) by FARR (FARR-RIA) has been utilized as the gold standard in the past for anti-dsDNA determination, detecting mostly high avidity antibodies. Additionally, enzyme-linked immunoassay (ELISA) and immunofluorescence (Crithidia luciliae) (CLIF) both recognize also low avidity anti-dsDNA and ELISA also detects antibodies against ssDNA. There is a need for replacing FARR-RIA with a safer and more environmentally friendly immunoassay. To modify the detection of anti-dsDNA by FARR-RIA, by replacing the radioactive isotope 14C and other toxic reagents and evaluate the newly developed, environmentally-friendly fluoroimmunoassay (FIA) for daily laboratory and clinical practice.

Methods: We tested 759 sequentially collected samples for anti-dsDNA testing, with FARR-RIA and FIA (using Picogreen® as intercalating dye). The group consisted of 146 blood donors, 70 SLE, 25 antiphospholipid syndrome, 28 rheumatoid arthritis, 25 Sjögren’s syndrome and 465 patients with unknown diagnoses. Final results of both methods were calculated from difference of signal measured between supernatant (S) and precipitate (P) divided by the sum of signals in S and P.

Results: At cut-off value of 0.35, both diagnostic specificity and sensitivity were comparable using FARR-RIA and FIA. Diagnostic specificity in both methods was 100%, while diagnostic sensitivity for FARR-RIA and FIA were 50% and 53%, respectively. Diagnostic accuracy for FIA was slightly lower compared to FARR-RIA, 0.781 vs. 0.887. There was comparable inter-accuracy of both methods in high positive results (CVFARR-RIA = 11%, CVFIA = 12%), while low positive results (CVFARR-RIA = 29%, CVFIA = 18%) showed greater variation. We confirmed comparable intra-repeatability in high positive results (CV = 2% for both methods) and low positive results (CVFARR-RIA = 33%, CVFIA = 28%). At high and low positive results comparable analytical accuracy was observed, while analytical sensitivity was higher in FIA. Neither ssDNA nor RNA affected the detection of anti-dsDNA. A correlation of 0.626 (p<0.01) was found between FARR-RIA and FIA positive results.

Conclusion: FIA and FARR-RIA showed comparable diagnostic specificity and sensitivity. Therefore, FARR-RIA could be replaced with FIA in daily laboratory routine practice for the detection of anti-dsDNA.

Disclosure: K. Lakota, None; T. Kveder, None; T. Svec, None; P. Žigon, None; A. Ambrozic, None; B. Božič, None; M. Tomšič, None; S. Čučnik, None; S. Sodin Semrl, None.

To cite this abstract in AMA style:

Lakota K, Kveder T, Svec T, Žigon P, Ambrozic A, Božič B, Tomšič M, Čučnik S, Sodin Semrl S. Detection of dsDNA Antibodies By New Fluoroimmunoassay with Comparable Diagnostic Sensitivity and Specificity to Farr-Ria [abstract]. Arthritis Rheumatol. 2017; 69 (suppl 10). https://acrabstracts.org/abstract/detection-of-dsdna-antibodies-by-new-fluoroimmunoassay-with-comparable-diagnostic-sensitivity-and-specificity-to-farr-ria/. Accessed .

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