B-082 Clinical Investigation of Rods and Rings Pattern in Anti-Nuclear Antibody Test in Korean Patients
Authors: Cho H , Park K , Kim Y , Park T , Cho S 
Published: October 2024

Abstract

Background
In the mid-2000s, a novel pattern in antinuclear antibody (ANA) testing was reported. Indirect immunofluorescence assays on HEp-2 cells, conducted with sera from patients with Hepatitis C virus (HCV) infection, revealed cytoplasmic structures in the form of rods and rings (RR). These structures typically displayed rod lengths of 3-10μm and ring diameters of 2-5μm. Inosine monophosphate dehydrogenase (IMPDH) was identified as the primary component of the RR structures. Research on the administration of interferon/ribavirin (IFN/RBV) showed that ribavirin, an IMPDH inhibitor, induced RR formation in over 95% of cells. Additionally, RR patterns were reported in patients receiving other IMPDH inhibitors such as mycophenolic acid and azathioprine. While cytidine triphosphate synthase 1 (CTPS1) was suggested to be associated with RR structures, there were no reported cases in patients. Interestingly, patients receiving methotrexate, which does not directly inhibit IMPDH but hinders GTP biosynthesis, also exhibited RR structures. To explore the clinical implications of specimens showing RR patterns, a study was conducted to investigate the actual clinical scenarios associated with these findings.

Methods
This is a retrospective study conducted at a single center, covering the period from January 2022 to December 2023, focusing on the results of ANA testing. The ANA tests were performed using HEp-2 cells (FLUORO HEPANA TEST, MBL, Nagoya, Japan) on slides manufactured with AP 16 IF Plus (das, Palombara Sabina, RM, Italy). ANA results were obtained through qualitative testing, ranging from 1+ to 4+, or quantitative testing based on dilutions ranging from 1:40 to 1:640, depending on clinical requirements.

Results
Out of the 7,648 ANA test results, the RR pattern was observed in 40 cases (0.5%). Among these, 2.5% had a history of HCV infection with IFN/RBV treatment, and an additional 2.5% had concurrent use of IMPDH inhibitors. There were no reported cases of medication history related to the synthetic pathway of nucleic acids, including CTPS1. Cases where RR patterns coexisted with autoimmune diseases accounted for 35%, infections for 25%, and other inflammatory conditions for 22.5%. RR patterns reported with an intensity of 3+ or at dilutions of 1:160 or higher constituted 27.5%. Among cases displaying strong fluorescence, 45% were associated with infections, 18% with autoimmune conditions, and another 18% with unexplained inflammatory causes. In the overall sample, elevated CRP or ESR was noted in 54.5% of cases with infections, autoimmune diseases, or other inflammatory conditions. Among samples with intense intensity, 55.5% showed elevated CRP or ESR when inflammatory conditions were present.

Conclusions
The majority of cases exhibiting the RR pattern showed no history of exposure to IMPDH inhibitors or drugs affecting the nucleic acid synthetic pathway. A high proportion of cases clinically diagnosed with inflammation showed a concurrent RR pattern, with only approximately half of them demonstrating elevated CRP or ESR levels. This study suggests the possibility of identifying inflammatory responses not captured by conventional acute inflammation markers through the RR pattern observed in ANA testing.