Utility of immunologic testing in suspected rheumatologic disease

Retrospective evaluation of "Rods and Rings" pattern detected in the anti-nuclear antibody (ANA) indirect immunofluorescence (IIF) test

Introduction

Anti-rods and rings (anti-RR) antibodies have recently been described as a cytoplasmic pattern in IIF-based screening of autoantibodies on HEp-2 cells and ICAP has named it as AC-23. It is most frequently related to drug-induced antibody generation. This study aimed to investigate the clinical significance of AC-23 positivity and its relevance to the diagnosis and/or follow-up of the associated diseases and/or drug use.

Methods

A multicenter retrospective study was conducted among 10 hospitals from six different provinces in Türkiye from January 2017 to December 2021. The laboratory data and clinical information of 600 patients with positive anti-RR antibodies out of 547.558 HEp-2 IIF ANA samples were analyzed.

Results

The distribution of AC-23 positive patients by year indicated a steady increase between 2017-2021. Anti-RR prevalence in post-COVID-19 period was significantly higher than that of pre-COVID-19 period (p=0.00). Concomitant ANA positivity was detected in 56.5% of patients, the most common patterns being AC-4 and AC-5 (41.1%). The most frequent pathology among the anti-RR positive patients was an autoimmune disease (19.83%); 28.57% of which had rheumatoid arthritis and 17.65% autoimmune liver disease. Among the 600 patients, 65 (10.83%) were diagnosed as hepatitis C virus (HCV) infection. Available data for 38 of the HCV patients revealed that 71.05% of them had a history of interferon alfa+ribavirin and 28.95% of them had a history of NS3/4/5A/5B polymerase inhibitor or protease inhibitor drug use. Significant increase in the rate of anti-RR positivity was observed in the post-COVID-19 period when compared to pre-COVID-19 period (p:0.00).

Discussion

This is the first multicenter study in Türkiye about the clinical association of anti-RR antibodies which may be ignored during routine HEp-2 IIF testing. Pathologies other than HCV should be taken into consideration in terms of the possible role of anti-RR in autoimmune diseases and other pathologies. The preliminary data obtained in this study suggest that anti-RR antibody development might also be associated to COVID-19, supporting the several previous data related to the potential of viruses triggering the formation of autoantibodies. Large-scale prospective studies should elucidate the clinical significance of RR pattern and determine its role in patient diagnosis and follow-up.

The clinical value of indirect immunofluorescence for screening anti-rods and rings antibodies: A retrospective study of two centers in China

Objective

To investigate the distribution and clinical significance of the rods and rings (RR) pattern in various diseases.

Methods

A total of 169,891 patients in Peking Union Medical College Hospital (PUMCH) and 29,458 patients in Inner Mongolia People’s Hospital (IMPH) from January 2018 to December 2020 were included, and the results of ANA (antinuclear antibodies) and special antibodies were analyzed retrospectively.

Results

The positive rates of ANA and RR patterns were 34.84%, 0.16% in PUMCH, and 44.73%, 0.23% in IMPH. Anti-RR antibodies mainly appear in adults (≥ 41 years), mostly of low or medium fluorescence titers. Isolated RR patterns were mostly presented (60.30% and 69.12%, respectively), and the RR pattern mixed with the speckled pattern was most commonly observed among patients having two or more patterns. The RR pattern existed in a variety of diseases including hepatitis C, AIDs, pulmonary diseases, nephropathy diseases, and even healthy people. The highest prevalence of the RR pattern was observed in hepatic diseases, such as hepatic dysfunction (0.79%), hepatic cirrhosis (1.05%), PBC (0.85%), and AIH (0.65%), etc. The positive rate of specific antibodies in RR pattern cases was 31.25%, and anti-Ro52 (27, 20.61%) was the most common target antibody.

Conclusion

The RR pattern had a low prevalence in ANAs test samples and varied in different nationalities and regions. Except for hepatitis C, it could be observed in AIDs, pulmonary diseases, nephropathy, other hepatic diseases, and even healthy people, but the positive rate was slightly higher in hepatic diseases. Its mechanism of action and clinical relevance still need clarification.

Abnormal antibodies: what do you do?

Systemic autoimmune rheumatic diseases encompass a vast array of autoantibodies which are very useful to confirm a suspected diagnosis. This article gives an overview of the most common autoantibodies, how they are tested and the significance of a positive test in a clinical context.