Only monospecific anti-DFS70 antibodies aid in the exclusion of antinuclear antibody associated rheumatic diseases: an Italian experience

Abstract

Background The dense fine speckled (DFS) is one of the most common patterns that can be observed as a result of the anti-nuclear antibodies (ANA) test on HEp-2 cells and is mostly caused by antibodies to DFS70 as the main antigenic target. As was recently demonstrated, isolated anti-DFS70 positivity can be used as an aid in the exclusion of ANA associated rheumatic diseases (AARD) due to the opportunity to better interpret unexplained positive IIF ANA results. Methods Our study included 333 subjects with AARD, 51 undifferentiated connective tissue disease (UCTD) patients, 235 disease controls and 149 healthy blood donors from an Italian cohort. All samples were tested for anti-DFS70 and anti-ENA antibodies using QUANTA Flash assays (Inova Diagnostics, San Diego, CA, USA). Results No differences in the prevalence of anti-DFS70 antibodies were seen among AARD, non-AARD and UCTD (2.1% [7/333] vs. 2.3% [9/384] vs. 5.9% [3/51], respectively; p-value = 0.188). AARD patients positive for anti-DFS70 antibodies showed in all cases an accompanying anti-ENA specificity. In contrast, monospecific anti-DFS70 antibodies showed a significantly different distribution with a clear trend across the main groups (AARD vs. non-AARD vs. UCTD: 0% [0/7] vs. 22% [2/9] vs. 100% [3/3], p = 0.007). Anti-DFS70 antibody levels among AARD, non-AARD and UCTD patients were not significantly different (p = 0.094). Within the anti-DFS70 antibody positive cases, AARD cohort showed a higher variability (median [min–max]: 3.2 [3.2–450.8] CU) compared to non-AARD (median [min–max]: 3.2 [3.2–75.7] CU) and UCTD patients (median [min–max]: 3.2 [3.2–59.0] CU). Conclusions Our preliminary data showed a similar frequency of anti-DFS70 antibodies in AARD, UCTD and non-AARD cohorts. Monospecificity of anti-DFS70 antibodies but not their mere presence is the key element in the diagnostic algorithm. Mono-specific anti-DFS70 antibodies might be a helpful biomarker to discriminate individuals with AARD from non-AARD presenting with a positive ANA.

Twenty years of research on the DFS70/LEDGF autoantibody-autoantigen system: many lessons learned but still many questions

“…Furthermore, when taking into consideration multiple studies across different countries and institutions, the frequencies of these antibodies in HI and SARD may not appear to be significantly different [70,92,95]. However, a distinctive feature of these antibodies in HI individuals is their relatively elevated frequencies as monospecific antibodies (only ANA detectable in the serum by HEp-2 IIFA), in contrast to patients with SARD in which these antibodies tend to appear concomitantly with other diseaseassociated ANAs [111][112][113]. These observations have led to the hypothesis that monospecific anti-DFS70/LEDGF autoantibodies may be considered as negative biomarkers to exclude a SARD diagnosis [100][101][102][103][104][105][106][107][110][111][112][113][114][115].…”

“…[70,92,95]). These variations have been attributed to confusion of the DFS IIF-ANA pattern with other patterns, different antibody detection substrates and platforms, and often the lack of specific confirmatory assays to support a positive anti-DFS70/LEDGF antibody identification [95,[112][113][114][115][116][117][118][119][120][121][122][123]. Fortunately, a plethora of new assays for the detection of these autoantibodies have been developed in recent years, providing excellent platforms for the confirmation of their presence in serum with high specificity and sensitivity (reviewed in Ref.…”

“…As mentioned above, while the prevalence of anti-DFS70/ LEDGF antibodies seems to be comparable in both HI and patients with SARD, typically ranging from 0 to 11% in both groups [70,92,95], they differ in their exclusivity, with monospecific antibodies more prevalent in HI than in patients with SARD [100][101][102][103][104][105][106][107][110][111][112][113][114][115]. However, monospecific anti-DFS70/LEDGF antibodies are not completely absent in SARD, since a recent international multicenter study led by Marvin Fritzler found a 1.1% frequency of these monospecific antibodies in a large cohort of patients with systemic lupus erythematosus (SLE) (13 out of 1137 patients) [127].…”

“…It has been recognized that the accurate recognition by clinicians of monospecific anti-DFS70/LEDGF antibodies, confirmed by other methods, will reassure patients and their families that a SARD diagnosis is unlikely, which would prevent unnecessary further testing, treatment, and distress to the patient [97,105,[112][113][114][115][127][128][129]. Recent studies have provided evidence that the introduction of an anti-DFS70/LEDGF autoantibody test in the clinic not only reduces unnecessary follow-up diagnostic procedures but also minimizes the use of costly health resources generated by suspicion of SARD [128,129].…”

Current laboratory and clinical practices in reporting and interpreting anti-nuclear antibody indirect immunofluorescence (ANA IIF) patterns: results of an international survey. 

“…The DFS pattern (AC-2) can vary depending on the manufacturer of the HEp-2 cell substrates (27,28) and its correct identi cation can be challenging, resulting in a high frequency of cases misclassi ed as DFS pattern (28). Furthermore, the assumed clinical relevance of the DFS pattern to exclude AARD only holds if the speci city is con rmed and if it is monospeci c for DFS70 (10,27,30). The inclusion of anti-DFS70 antibody testing in a diagnostic algorithm or re ex testing is currently under discussion (31,32).…”