Agreement between local and central anti-synthetase antibodies detection: results from the Classification Criteria of Anti-Synthetase Syndrome project biobank

OBJECTIVES

The CLASS (Classification Criteria of Anti-Synthetase Syndrome) project is a large international multicentre study that aims to create the first data-driven anti-synthetase syndrome (ASSD) classification criteria. Identifying anti-aminoacyl tRNA synthetase antibodies (anti-ARS) is crucial for diagnosis, and several commercial immunoassays are now available for this purpose. However, using these assays risks yielding false-positive or false-negative results, potentially leading to misdiagnosis. The established reference standard for detecting anti-ARS is immunoprecipitation (IP), typically employed in research rather than routine autoantibody testing. We gathered samples from participating centers and results from local anti-ARS testing. As an "ad-interim" study within the CLASS project, we aimed to assess how local immunoassays perform in real-world settings compared to our central definition of anti-ARS positivity.

METHODS

We collected 787 serum samples from participating centres for the CLASS project and their local anti-ARS test results. These samples underwent initial central testing using RNA-IP. Following this, the specificity of ARS was reconfirmed centrally through ELISA, line-blot assay (LIA), and, in cases of conflicting results, protein-IP. The sensitivity, specificity, positive likelihood ratio and positive and negative predictive values were evaluated. We also calculated the inter-rater agreement between central and local results using a weighted κ co-efficient.

RESULTS

Our analysis demonstrates that local, real-world detection of anti-Jo1 is reliable with high sensitivity and specificity with a very good level of agreement with our central definition of anti-Jo1 antibody positivity. However, the agreement between local immunoassay and central determination of anti-non-Jo1 antibodies varied, especially among results obtained using local LIA, ELISA and "other" methods.

CONCLUSIONS

Our study evaluates the performance of real-world identification of anti-synthetase antibodies in a large cohort of multi-national patients with ASSD and controls. Our analysis reinforces the reliability of real-world anti-Jo1 detection methods. In contrast, challenges persist for anti-non-Jo1 identification, particularly anti-PL7 and rarer antibodies such as anti-OJ/KS. Clinicians should exercise caution when interpreting anti-synthetase antibodies, especially when commercial immunoassays test positive for non-anti-Jo1 antibodies.

10-year experience of early arthritis clinic at a tertiary rheumatology center: achievements and challenges

OBJECTIVES

To characterize patients evaluated in our Early Arthritis Clinic (EAC) in the first ten years; to assess diagnostic delay and its underlying causes; and to evaluate the level of agreement between the referring physician and the rheumatologist regarding the presence of referral criteria.

METHODS

Cross-sectional study including patients attending EAC between 2012 and 2021. Demographic data, provenience, final diagnosis, referral criteria and time related to diagnosis delay were retrieved from clinical files and the Portuguese Registry of Rheumatic Patients (reuma.pt). Characteristics of the patients and the time variables were analysed with descriptive statistical analysis. The agreement between the referring physician and rheumatologist regarding the referral criteria was evaluated using Cohen's Kappa.

RESULTS

A total of 440 patients (68.9% females, mean age of 54±16.7 years) were referred, mostly from primary care (71.6%). Inflammatory Rheumatic Disease was diagnosed in 65.7% of the patients, with 58.9% classified as early arthritis. The median time from onset of symptoms to referral for EAC was 76 days (IQR 33.5-144.0); the median time from referral to the first EAC was 34 (IQR 19.0-46.0) days, and the median time from onset of symptoms to first EAC was 114.5 (IQR 66.8-190.3) days (16.3 weeks). Only about 10% were observed by a Rheumatologist before six weeks after symptom onset. The level of agreement between the referring physician and the rheumatologist was slight to fair to clinical criteria and moderate to substantial to laboratory criteria.

CONCLUSIONS

A significant delay still is observed in patients with early arthritis suspicion, being the time from onset of symptoms to referral is the most relevant. A low agreement between referral and Rheumatologists suggests that non-rheumatologists education/training is needed. Identifying the barriers that prevent the adequate referral of patients is necessary to define strategies to improve it.

Parameniscal cyst: an important differential diagnosis in slow growing masses of the knee

INTRODUCTION

Parameniscal cysts are small cystic lesions, near the meniscus, involving medial and lateral compartments at equal frequency. Frequently, parameniscal cysts are so small that patients do not notice them, being asymptomatic. However, they can grow and exceed 2 centimeters in diameter, causing pain and alarm due to the slow growing mass. Magnetic Resonance Imaging (MRI) is the gold standard for diagnosis.

METHODS

Case report of a patient admitted to rheumatology department in the Centro Hospitalar e Universitário de Coimbra.

RESULTS

We report a case of a 47-year-old male with idiopathic juvenile arthritis, who presented with a slow-growing mass over the medial aspect of the right knee. MRI revealed a conspicuous cystic ovoid lesion, compatible with a parameniscal cyst, associated with structural heterogeneity of the posterior edge of the internal meniscus with a longitudinal fracture at this level.

CONCLUSION

This is the first case of parameniscal cyst reported in patients with inflammatory rheumatic disease and the differential diagnosis with synovial cyst, baker cyst, ganglion cyst, bursitis, hematoma and neoplasms is of utmost importance.