Background/Purpose: ANA prevalence and patterns vary in RA. Using ICAP nomenclature, this study aimed to determine the prevalence of RA across different ANA patterns and the distribution of these patterns in RA patients within a large Taiwanese cohort.

Methods: This cross-sectional study used the Chang Gung Research Database (2019-2021). Patients undergoing ANA IIF testing (HEp-2 substrate, ≥1:100 positive) were included. Patients with inconsistent/mixed patterns were excluded from pure pattern analysis. RA diagnosis used ICD codes confirmed by rheumatologists. RA prevalence and odds ratios (ORs) were calculated for each ANA pattern (AC-1 to AC-29) versus ANA-negative (AC-0). ANA pattern/titer distributions were compared between RA and non-RA cohorts.

Results: Among 35,763 patients with single, consistent ANA patterns, 4,612 (12.9%) were ANA-positive. RA prevalence in the AC-0 group was 4.62%. Significantly higher RA prevalence occurred with AC-2 (Dense fine speckled, 11.92%, OR 2.80), AC-1 (Homogeneous, 10.02%, OR 2.30), AC-4 (Fine speckled, 9.85%, OR 2.26), and AC-5 (Coarse speckled, 8.95%, OR 2.03) patterns (all p< 0.001). In the RA cohort (n=1,860 with pure patterns), ANA positivity was 22.69% (vs. 12.38% in non-RA, p< 0.0001), with higher titers. The most frequent patterns in ANA-positive RA were Speckled (AC-4/AC-5, 8.66%), Dense fine speckled (AC-2, 4.03%), Homogeneous (AC-1, 3.01%), and Centromere (AC-3, 2.26%).

Conclusion: Specific ANA patterns (AC-1, AC-2, AC-4, AC-5) are significantly associated with increased RA prevalence in this Taiwanese cohort. RA patients show higher ANA positivity and titers, favoring speckled, dense fine speckled, and homogeneous patterns. Detailed ICAP pattern reporting is clinically relevant for RA assessment.

Table 1. Prevalence of Rheumatoid Arthritis Across Different Pure ANA Staining Patterns Compared to ANA-negative Patients

Figure 1. Flowchart illustrating the distribution of ANA patterns (AC-1 to AC-29) among rheumatoid arthritis patients tested at Chang Gung Memorial Hospital (2019–2021)

Figure 2. Distribution of Pure-Single ANA Patterns in ANA-Positive Rheumatoid Arthritis Patients

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/rethinking-ana-in-rheumatoid-arthritis-icap-pattern-insights-from-a-large-scale-taiwanese-cohort/