AB1018 Detection of ANTI-DFS70 antibodies by indirect immunofluorescence (IIF) on novel HEP-2/DFS70-KO substrate for discriminating antinuclear antibodies (ANA) – positive healthy individuals (HI) and patients with systemic lupus erythematosus (SLE)

Abstract

BackgroundAutoantibodies against intracellular antigens are a serological hallmark of ANA-associated systemic autoimmune rheumatic diseases (AARD) such as SLE. IIF on HEp-2 cells for ANA remains the “gold standard” but it has very low positive predictive value. Up to 20% of serum samples from HI have been reported to have a positive ANA IIF test, the majority of them due to the presence of anti-dense fine speckled 70 (anti-DFS70) antibodies. Monospecific anti-DFS70 antibodies represent a biomarker that can be used to discriminate AARD patients (pts) from HI in ANA IIF positive subjects. Recognition of the DFS70 ANA IIF pattern can be challenging. The DFS-KO Hep-2 cells inhibit anti-DFS70 antibodies reactions, providing clear differentiation of the DFS pattern from classical ANA patterns.ObjectivesTo evaluate the utility of a novel HEp-2/DFS70-KO IIF substrate for the detection of anti-DFS70 antibodies in HI and SLE pts.MethodsWe studied 45 HI (36 F/9 M; age 50.4 [24.0–72.0] years, median [interquartile range 25–75%]) and 12 pts with SLE (ACR criteria, 1997) (10 F/2M, age 38.9 [17.0–65.0] years; disease duration 100.3 [4.0–432.0] months; SLEDAI 2K score 11.7 [2–30]; SLICC damage index score 1.28 [0–4]). Serum samples were tested for classical ANA and anti-DFS70 antibodies by IIF technique with a mixture of standard HEp-2 cells and DFS70-KO HEp-2 cells (“Trinity Biotech”, Bray, Ireland) as a substrate. Fluorescence titers ≥1: 160 were considered as positive for ANA patterns.ResultsANA were present in 7/45 (15.6%) of HI and in 12/12 (100%) of SLE pts. All SLE pts and 3/45 (6.7%) of HI showed classic ANA patterns (homogeneous, speckled, and mixed) in the absence of DFS70 pattern. 4/45 (8.9%) of HI had classic ANA negative/anti-DFS70 antibodies positive IIF results. Isolated anti-DFS70 antibodies were found in 57% of ANA IIF positive HI. Among HI classic ANA and anti-DFS70 antibodies were detected in the low- to medium-titer range (1:160–1:320). The frequency of anti-DFS70 antibodies did not correlated with age.ConclusionsThe detection of isolated anti-DFS70 antibodies may be regarded as an exclusion criterion for the diagnosis of SLE. The testing for anti-DFS70 antibodies in a single step by HEp-2/DFS70-KO IIF method should be included into a modified ANA diagnostic algorithm. Additional investigations are required to evaluate the clinical relevance of anti-DFS70 autoantibodies.Disclosure of InterestNone declared

The Role of Anti-DFS70 in the Diagnosis of Systemic Autoimmune Rheumatic Diseases

“…Among ANA-positive healthy individuals, the frequency of isolated detection of antibodies to anti-DFS70 was 57%. The authors concluded that monospecific antibodies to anti-DFS70 serve as a negative serological marker for SLE [62]. However, in some studies, an assessment of their potential association with serological and clinical manifestations and disease activity has been conducted.…”

Anti-DFS70 antibodies are more prevalent in UCTD and Asian SLE patients

“…[6], cancers (e.g., prostate cancer, breast cancer, etc.) [7,8] and healthy individuals (HI) [6, [9][10][11][12][13][14][15][16][17]. As an antinuclear autoantibody (ANA), most studies have focused on the clinical association between anti-DFS70 and systemic autoimmune rheumatic diseases (SARD) [6, 14,18], reporting that anti-DFS70 prevalence is comparable in SARD and in HI [19] unlike other autoantibodies which are common in different types of SARD.…”