Ab1235 Evaluation of the Relationship Between Gastrointestinal Involvement Characteristics and Anti Muscarinic Receptor 3 Antibodies in Patients With Systemic Sclerosis

Background: Gastrointestinal tract (GIS) involvement is a leading cause of morbidity in systemic sclerosis (SSc). Non-invasive biomarkers are needed for GI involvement. The role of anti-muscarinic 3 receptor (anti-M3R) antibodies in the pathogenesis of GI tract involvement has been demonstrated. Objectives: The aim of this study was to investigate the relationship between GI uptake characteristics and serum anti-M3R antibodies in SSc patients. Methods: This study was conducted with 41 SSc patients and 5 healthy controls. GI complaints of all patients were questioned. MUST and ESPEN scores were calculated for malnutrition and UCLA SCTC GIT 2.0 scores were calculated for the severity of GI involvement. Sandwich-ELISA test was used to detect anti-M3R antibody (MyBioSource, Inc. San Diego, USA). Anti-M3R antibodies were tested in 39 patients because the blood samples of two patients were haemolysed. The relationship between serum anti-M3R antibody titres and patients' clinical characteristics, GI symptoms and malnutrition scores were evaluated. Results: Thirty-one (85.4%) of the patients were female, 32 (78%) had a diagnosis of limited SSc, mean age was 53.6 ± 13.5 years, median disease duration (IQR) was 15 (6.00-20.50) years. 37 (90.2%) patients had GIS involvement. Anti-M3R antibody was positive in 18 (46.1%) patients. Anti-M3R antibodies were negative in all (n=5) patients with positive anti-centromere antibodies and positive in all (n=4) patients with myositis (Table 1). According to the total UCLA SCTC GIT 2.0 score, no correlation was found between moderate to severe GIT involvement and anti-M3R antibody titres (all parameters, p >0.05). Anti-M3R antibody titres and the number of antibody positive patients were not different between the patient groups with and without risk of malnutrition according to MUST score (all parameters, p>0.05). Anti-M3R antibody titres and the number of antibody-positive patients were not different between the patient groups with and without malnutrition determined using ESPEN criteria (p>0.05). In terms of clinical characteristics, anti-M3R antibody titres were found to be lower in patients with faecal incontinence compared to those without (p=0.05). There was a tendency for higher antibody titres in patients with weight loss compared to those without weight loss, but it did not reach a significant level (p=0.09). The comparison of antibody titres according to clinical and laboratory characteristics is given in Table 2. Conclusion: In this study, a significant rate of anti-M3R antibody positivity was detected in SSc patients. No association was found between anti-M3R antibody positivity or titres and total UCLA SCTC GIT 2.0 score or malnutrition risk. REFERENCES: NIL. Table 1. Demographic and clinical characteristics of systemic sclerosis patients according to anti-M3R antibody positivity Table 2. Anti-M3R antibody titers according to the disease type, autoantibody profile, organ involvement and immunosuppressive therapy usage Acknowledgements: The authors thank all contributors. Disclosure of Interests: None declared.