Abstract
A dense fine speckled pattern (DFS) caused by antibodies to the DFS70 kDa nuclear protein is a relatively common finding while testing for anti-nuclear antibodies (ANA) by indirect immunofluorescence (IIF) on HEp-2 cells. However, despite many efforts and numerous studies, the clinical significance of anti-DFS70 antibodies is still unknown as they can be found in patients with various disorders and even in healthy subjects. In this study we aimed at verifying whether these antibodies are associated with thrombotic events or with unexplained recurrent pregnancy loss (RPL). We studied 443 patients with venous or arterial thrombosis or RPL and 244 controls by IIF on HEp-2 cells and by a DFS70-specific chemiluminescent immunoassay (CIA). The DFS pattern was observed in IIF in 31/443 (7.0%) patients and in 6/244 (2.5%) controls (p = 0.01) while anti-DFS70 specific antibodies were detected by CIA in 11 (2.5%) patients and in one (0.4%) control (p = 0.06). Positive samples, either by IIF or by CIA, were then assayed by a second DFS70-specific line-immunoassay (LIA) method: 83.3% of the CIA positive samples were confirmed DFS70 positive versus only 29.7% of the IIF positive samples. These findings show that IIF overestimates anti-DFS70 antibody frequency and that results obtained by specific CIA and LIA assays do not indicate that venous or arterial thrombosis or RPL are linked to a higher prevalence of anti-DFS70 antibodies.
Highlights
A dense fine speckled pattern (DFS) caused by antibodies to the DFS70 kDa nuclear protein is a relatively common finding while testing for anti-nuclear antibodies (ANA) by indirect immunofluorescence (IIF) on HEp-2 cells
The dense fine speckled pattern was observed in IIF in 31/443 (7.0%) patients (27 women and 4 males) at a titer ranging from 1:80 to 1:2560: eight had anti-phospholipid syndrome (APS), eight had venous thromboembolism (VTE), four had arterial thrombosis, ten had recurrent pregnancy loss (RPL), one had thrombosis in treatment with heparin, and in 6/244 (2.5%; p = 0.01) controls
Anti-DFS70 antibodies were detected by chemiluminescent immunoassay (CIA) in 11/443 (2.5%) patients (9 women and 2 males; mean value, 118 chemiluminescent units (CU); range, 23.9-450): two with APS, two with VTE, one with arterial thrombosis, five with RPL, one with thrombosis on treatment with heparin, and in 1/244 (0.4%) control with atrial fibrillation (43.8 CU) (p = 0.06) (Fig. 1)
Summary
A dense fine speckled pattern (DFS) caused by antibodies to the DFS70 kDa nuclear protein is a relatively common finding while testing for anti-nuclear antibodies (ANA) by indirect immunofluorescence (IIF) on HEp-2 cells. Despite many efforts and numerous studies, the clinical significance of anti-DFS70 antibodies is still unknown as they can be found in patients with various disorders and even in healthy subjects. To further complicate matters in the quest to establish their possible clinical association, it has been seen that their prevalence reported in different cohorts of diseased subjects as well as in healthy individuals is dependent on the detection method employed Their recognition by IIF is not standardized, being highly related to the characteristics (brand) of the HEp-2 substrates used and to the experience of the readers[16,17]. In one study it was found that these systems are able to recognize 85% of the homogeneous patterns and 78% of the speckled patterns, but none of the samples with the DFS70 pattern that are classified either as homogeneous or speckled[19]
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