Background Diagnosis of systemic lupus erythematosus (SLE) is a sophisticated problem in most of the disease cases. The reasons of this include common diagnostic markers of SLE (ANA, anti-dsDNA, anti-Sm), that are insufficiently reliable itself as well. One of possible ways to overcome these difficulties is searching for new SLE markers. These emerging diagnostic tools are not only to be valuable for diagnosis establishment, but also to provide economical efficiency and facility in common use.
Objectives To compare diagnostic efficiency of anti-DNase I antibodies measured by conventional ELISA and by originally modified enzyme immunosorbent assay using magnetic polyacrylamide beads as an antigen carrier.
Methods The research was carried out in agreement with the WMA Declaration of Helsinki principles, it was approved by the Regional Committee on Medical Ethics. All the patients signed the informed consent. We have enrolled 54 in-hospital adult patients with SLE, verified by the ACR criteria (1997). Control group (n=52) was comprised of patients with rheumatoid arthritis, systemic sclerosis, systemic vasculitides, dermatomyositis, and Sjogren's disease. Serum anti-DNase I concentrations were evaluated by conventional ELISA, as described elsewhere . The beads were synthesized using original technique , modified ELISA and recovery of the beads for repeating use was performed according to the previously published protocols . Antibody concentrations were expressed as relative optical density units (ODU). The cutoff values for conventional and modified ELISA were 0.061 and 0.057 ODU, respectively. All the means and operation characteristics were expressed as values (95% confidence intervals). Differences were considered significant when p<0.05.
Results Mean anti-DNase I concentrations in SLE patients (negative and positive together) were 0.088 (0.031–0.145) and 0.079 (0.033–0.125) ODU for conventional and modified ELISA, respectively; in the control group they were 0.068 (0.020–0.116) and 0.063 (0.019–0.107) ODU, respectively. Differences within these couples were not significant. Diagnostic sensivity and specificity of modified ELISA were 64.74 (53.09–76.39) and 85.01 (72.95–97.07)%, coinciding with those for conventional ELISA. LOQ for the modified ELISA was slightly lower than for the conventional one. Accuracy and repeatability of modified ELISA were also insignificantly higher than those for conventional approach. There was no substantial change in all the parameters of modified ELISA after single recovery of beads.
Conclusions The newly developed ELISA for anti-DNase I antibodies was demonstrated to have equivalence or advantage in some analytical parameters over conventional ELISA. Considering some economic and maintenance benefits, our innovation can be an alternative tool to improve SLE diagnostics.
Trofimenko AS, Gontar IP, Zborovsky AB, Paramonova OV. Anti-DNase I antibodies in systemic lupus erythematosus: diagnostic value and share in the enzyme inhibition. Rheumatol Int. 2016;36(4):521–9.
Gontar IP, Simakova ES, Trofimenko AS, Zborovskaya IA. An approach for removal of DNA-containing immune complexes from blood using composite sorbent. Patent RU2441674 (2010) [in Russian].
Disclosure of Interest None declared