Background/Purpose: Anti-Synthetase Syndrome (ASyS) is a rare systemic autoimmune disease defined by a combination of pulmonary, muscle, joint, and skin manifestations and the presence of antibodies (Aab) targeting a tRNA t-synthetase. The anti-Jo1 (Histidyl-t-RNA-synthetase) antibody is the most commonly found and can be quantified by Luminex® technology. The aim of this study was therefore to evaluate the value of indirect quantification by LUMINEX® technology of anti-Jo1 Aab as a prognostic factor and biomarker of activity.

Methods: We conduct a retrospective, bi-centric study beetween the Pitié Salpêtrière Hospitals and Reims University Hospital Centre. ASyS diagnostic was defined by the presence of at least 2 clinical manifestations associated with this Aab.

Severity was defined by the need for mechanical intubation-ventilation, hypoxemia < 60 mmHg PaO2, the presence of proven cardiac injury, severe muscle injury with bed confinement, diaphragmatic injury, or the presence of swallowing difficulties. Activity assessment was rated using the tools recommended by IMACS and ACR/EULAR and was represented on a numerical scale summarizing the practitioner's overall assessment. Quantification of Anti-Jo1 Aab was performed using a Luminex® approach (Euroline Myositis Profile 3: Euroimmun).

Results: Among the 99 patients followed for SAS, 27 were excluded for lack of information. Patients from sub-Saharan Africa and the Caribbean were more represented in the group with a complication at diagnosis (23% vs. 9%, p=0.04). The anti-Jo1 Aab titer (209 [176.8-257.3] vs 128 [89.5-169]; p< 0.001), as well as the CK level (3350 [1486-15000] vs 1078 [246-4125] p< 0.05) were higher in the severe event group. For the 37 patients whose titer was available at diagnosis, one or more controls were available for 24 patients. The median titre of Jo1 antibody was higher at diagnosis compared to the corresponding assay at the time of clinical remission (171.5 [113.3-232.3] vs 137 [90-160.3] p=0.02). The maximum anti-Jo1 antibody titer was significantly higher in the patient with severe event than the no severe event group (229.5 [182-272.3] vs 149.5 [118.8-184.3] p< 0.001). The ROC curve produced had an area under the curve of 0.81 IC95(0.71-0.91) p< 0.001. A value of anti-Jo1 Ac > 186 had a sensitivity of 74% and a specificity of 79% to predict the risk of a serious event.

Of the 33 patients with a titer > 186, 70% had a serious event in follow-up, of which 50%, the vast majority, occurred within the first 30 days of follow-up. Conversely, only 21% of patients with a titer < 186 had an event during follow-up.

Conclusion: Indirect quantification of Ac anti-Jo1 by fluorescence intensity using the Luminex technology was correlated with the occurrence of serious events in the monitoring of ASyS. It was a reliable, reproducible and automated technique that could be used to assist in patient follow-up and treatment monitoring. The validation of these results on independent cohorts is nevertheless necessary.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/anti-jo1-antibody-quantification-serve-as-a-prognostic-factor-in-anti-synthetase-syndrom/