Background and aims The prevalence of ANA-negative SLE is reportedly 5%–20%. Cytoplasmic or mitotic cell indirect immunofluorescence (IIF) patterns are usually reported as ANA-negative. This study examined the prevalence of ANA-negativity (no intracellular IIF pattern) and pure cytoplasmic and/or mitotic IIF patterns (CMP) in the Systemic Lupus International Collaborating Clinics (SLICC) inception cohort and examined demographic, clinical and autoantibody associations.
Methods Three groups were examined 1) ANA-positive (presence of nuclear IIF pattern), 2) ANA-negative (no IIF pattern), and 3) pure CMP. ANA were detected by IIF on HEp-2000 substrate, SLE-related autoantibodies by laser bead immunoassay, and anti-dsDNA and anti-dense fine speckles 70 (DFS70) by chemiluminescence immunoassay.
Results 1137 patients were included; 89.9% were female. 92.3% were ANA-positive, 6.2% were ANA-negative, and 1.5% had a CMP. In the multivariate analysis (Tables 1 and 2), patients from Canada (Odds Ratio (OR) 2.07 [95% CI: 1.28, 3.36]) or with anti-DFS70 (OR 4.45 [95% CI: 1.37, 14.39]) were more likely to be ANA-negative or have CMP. Patients of Asian descent (OR 0.34 [95% CI: 0.13, 0.86]) or with anti-dsDNA (OR 0.53 [95% CI: 0.30, 0.94]), anti-SSA/Ro60 (OR 0.51 [95% CI: 0.30, 0.87]), or anti-UI-RNP (OR 0.35 [95% CI: 0.17, 0.70]) were less likely to be ANA-negative or CMP.
Conclusions In newly diagnosed SLE, the prevalence of ANA-negativity was at the lower end (6.2%) of the range previously published and an additional 1.5% had a CMP pattern. The prevalence of true ANA-negativity will likely decrease as future guidelines are expected to recommend that non-nuclear patterns, such as CMP, are also reported.
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