Relevance of anti-nucleosome antibodies detected by enzyme – based immunoassays in lupus diagnosis. Comparative analysis of three commercial kits

Overview

The aim of this study is to evaluate three commercial anti-nucleosome enzyme-linked immunosorbent assays (ELISA), to find the presence anti-nucleosomal antibodies (Ncs–Ab) and to report our experience with the detection of anti-nucleosome (anti-Nuc) antibodies (Ab) in series of SLE patients, and to compare these results with those of anti-histone and anti-dsDNA Ab.

Patients and methods.
We selected 128 patients (106 female, 22 male, mean age 40) including 52 patients with SLE, 14 with lupus nephritis, 8 with neuropsychiatric lupus (NPSLE) and as controls 39 with systemic sclerosis (SCL), 15 with Sjögren syndrome and 51 healthy controls (40 female, 11 male, mean age 42) and to evaluate three commercial ELISA kits (Orgentec, BL Diagnostika, Euroimmun). The sera were assayed for the levels of anti-ds DNA (ELISA, Orgentec), anti-histone (INNO LIA ANA Update, Innogenetics) also.

Results.
The prevalence of positive anti-nucleosome was by detection Orgentec, BL Diagnostika and Euroimmun in group of patients with SLE 99,3 %, 99,3% and 72,3%, with lupus nephritis 100 %, 100 % and 79 %, with NPSLE 100 %, 100 % and 62,3%, with SCL 82,1 %, 82,1 %, 17,9 % , with SS 14%, 14% and 7% and with healthy controls 8 %, 8 % and 6 %, respectively. The frequencies of positive anti-nucleosome, anti-dsDNA and anti-histone antibodies were in group of patients with SLE 73 %, 63 % and 54%, with SCL 17,9 %, 8 %, 5 % and with SS 7 %, 7 % and 0 %, respectively. Patients with SLE have increased levels of anti-nucleosome antibodies in their sera compared with healthy controls, SCL patients and patients with SS.

Conclusion.
Based on frequency of positive observations of anti-Ncs Ab in the group of patients suffering with SLE (62,3-79%) and discrepancy findings in the group with SCL patiens (82,1 %, p<0,001) by using Orgentec and BL Diagnostika we decided to introduce the kit by Euroimmun (17,9 %, NS) for rutine use. The results obstained using this kit are in good corelation with results published so far. All the three autoantibodies were present more frequently in cases with lupus and this corelation was significant in statistical means.

Key words:
SLE - systemic lupus erythematosus, SCL - sclerodermia, SS - Sjögren syndrome, anti-nucler antibodies, anti-histone antibodies, anti-ds DNA antibodies, anti-nucleosomal antibodie