Celiac disease (CD) is a chronic systemic autoimmune disorder triggered by gluten ingestion in genetically susceptible individuals, primarily affecting the small intestine and causing characteristic villous atrophy [1]. Type 1 Diabetes Mellitus (T1DM) and CD share a strong genetic association through Human Leukocyte Antigen (HLA) class II molecules, particularly HLA DQ2 and HLA DQ8, which are present in over 90% of celiac patients and constitute major risk factors for T1DM [2]. The clinical association between T1DM and CD was first reported in 1969 [3]. Since then, numerous international studies have consistently demonstrated that patients with T1DM constitute a high-risk group for developing celiac disease, with prevalence rates ranging from 2% to 11%, representing approximately 10-20 times higher risk than the general population [4-6]. This elevated risk is primarily attributed to shared HLA susceptibility genes that predispose individuals to both autoimmune conditions [2]. The clinical presentation of CD in T1DM patients is predominantly silent or atypical, with most cases being asymptomatic at diagnosis [7-9]. This clinical silence necessitates active screening approaches, as symptom- based case-finding would miss the majority of affected patients. Major international organizations, including the International Society for Pediatric and Adolescent Diabetes ISPAD) and the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition ESPGHAN , recommend routine screening for CD in all T1DM patients [10,11]. In India, celiac disease is increasingly recognized as a significant public health problem, particularly in northern states where wheat constitutes a dietary staple. Previous Indian studies have reported high CD prevalence in T1DM patients, with Bhadada et al. (2011) documenting 11.1% biopsy-proven prevalence in North India [12], and Sharma et al. (2022) reporting 5.5% prevalence in pediatric T1DM patients [13]. Despite this growing evidence, significant knowledge gaps remain regarding regional prevalence patterns across India. North West Rajasthan represents an understudied region with distinct genetic backgrounds, dietary patterns, and healthcare infrastructure that may influence disease prevalence and presentation. The absence of local epidemiological data hampers the development of evidence-based screening protocols and appropriate resource allocation. This study aims to determine the prevalence of celiac disease in patients with Type 1 Diabetes Mellitus in North West Rajasthan and characterize the associated clinical and demographic factors to inform regional healthcare policy and clinical practice.

Study Design and Setting This hospital-based, cross-sectional observational study was conducted at the Department of General Medicine, S.P. Medical College and P.B.M. associated Group of Hospitals, Bikaner, North West Rajasthan, over a 6-months period from February 2025 to July 2025. The study received ethical approval from the Institutional Ethics and Research Board of S.P. Medical College, Bikaner. Study Population and Sample Size The study population comprised patients with T1DM attending outpatient clinics or admitted to wards during the study period. A sample size of 100 was calculated using single population proportion formula with 95% confidence level, estimated prevalence of 25% based on previous studies, and margin of error of 8.5% [14]. Inclusion criteria: Patients with confirmed T1DM according to American Diabetes Association criteria [15], consuming gluten-containing diet, and providing informed consent. Exclusion criteria: Pre-existing biopsy-confirmed CD, gluten-free diet for 2 weeks, documented IgA deficiency without appropriate IgG-based screening, critically ill patients, and those refusing consent. Data Collection and Procedures: Consecutive sampling was employed until target enrollment was achieved. Comprehensive clinical history, demographic data, and family history were collected using standardized case record forms. All participants underwent: Serological screening: 5ml venous blood samples were analyzed for anti-tissue transglutaminase (tTG) IgA antibodies and total serum IgA levels. IgA-deficient patients were screened using anti-deamidated gliadin peptide DGP IgG antibodies. Histological confirmation: Patients with positive serology (tTG IgA 10 U/mL) underwent upper gastrointestinal endoscopy with multiple duodenal biopsies (≥4 from distal duodenum, ≥1 from duodenal bulb). Histopathological examination used Marsh-Oberhuber classification for grading mucosal damage [16]. Laboratory Methods: TTG IgA antibodies were measured using enzyme-linked immunosorbent assay (ELISA) with cutoff value 10 U/mL considered positive. Additional laboratory investigations included serum ferritin, hemoglobin, fasting glucose, and HbA1c levels using standard automated analyzers. Statistical Analysis: Data analysis was performed using Statistical Package for Social Sciences (SPSS) version 25.0. Descriptive statistics included means and standard deviations for continuous variables, frequencies and percentages for categorical variables. Chi-square test assessed associations between categorical variables, while independent samples t-test compared continuous variables. P-values 0.05 were considered statistically significant.

Baseline Characteristics: A total of 100 T1DM patients were enrolled, comprising 56 males and 44 females, with mean age 28.9 ± 6.9 years (range 15- 40 years). The mean T1DM duration was 12.5 ± 6.2 years (range 3-27 years). Parameter Total Patients (n=100) CD Positive (n=12) CD Negative (n=88) P value Age (years), Mean ± SD 28.9 ± 6.9 29.8 ± 7.6 28.8 ± 6.9 0.622 Female gender, n % 44 (44%) 10 (83.3%) 34 (38.6%) 0.009 T1DM Duration (years), Mean ± SD 12.5 ± 6.2 14.9 ± 3.2 12.2 ± 6.5 0.157 BMI (kg/m²), Mean ± SD 21.4 ± 5.1 20.2 ± 3.5 21.5 ± 5.3 0.414 Table 1 Baseline Demographic Characteristics of Study Population Primary Outcome: Prevalence of Celiac Disease Biopsy-confirmed celiac disease was diagnosed in 12 patients, yielding a prevalence of 12.0% with 95% CI 6.6- 20.4%. This represents a 10-fold higher prevalence compared to general population estimates of 1-1.2%. Gender-wise Distribution Female patients demonstrated significantly higher CD prevalence than males 22.7% vs 3.6%, p=0.005, representing a 6.3-fold increased risk. This gender disparity exceeded many reported ratios in global literature and suggests amplified hormonal or genetic effects in our regional population. Table 2 Gender-wise Distribution of Celiac Disease Prevalence Gender Total Patients CD Positive CD Negative Prevalence % P-value Male 56 (56%) 2 (3.6%) 54 (96.4%) 3.6% 0.005 Female 44 (44%) 10 (22.7%) 34 (77.3% ) 22.7% Total 100 (100%) 12 (12% ) 88 (88% ) 12.0% Figure 1: Gender-wise Distribution of Celiac Disease Prevalence in T1DM Patients Clinical Presentation Patterns Iron-deficiency anemia emerged as the most discriminating clinical feature, present in 83.3% of CD patients compared to 10.2% of controls OR 43.89, p<0.001. Fatigue was universal in all CD patients 100%, while abdominal pain/bloating was present in 75.0% of CD patients versus 39.8% of controls OR 4.54, p=0.046. Table 3 Clinical Manifestations and Statistical Analysis Clinical Manifestation CD Positive (n=12) CD Negative (n=88) Odds Ratio P-value Chronic Diarrhea 4 (33.3%) 9 (10.2%) 4.39 0.076 Abdominal Pain/Bloating 9 (75.0%) 35 (39.8%) 4.54 0.046 Iron-deficiency Anemia 10 (83.3%) 9 (10.2%) 43.89 0.001 Fatigue 12 (100.0%) 47(53.4%) N/A 0.001 Recurrent Stomatitis 2 (16.7%) 2 (2.3%) 8.60 0.109 Figure 2: Comparison of Clinical Manifestations between CD Positive and CD Negative T1DM Patient Laboratory and Diagnostic Parameters TTG IgA testing demonstrated exceptional diagnostic performance with 100% sensitivity and 100% specificity at the 10 U/mL cut off. CD patients had significantly higher TTG IgA levels 94.8 ± 61.7 vs 1.8 ± 0.9 U/mL, (p<0.001) and lower serum ferritin levels 29.3±14.7 vs 52.9 ± 19.2 ng/mL, p<0.001 , reflecting malabsorption effects. Table 4 Laboratory Parameters and Diagnostic Markers Parameter CD Positive (n=12) CD Negative (n=88) P value 95% CI for Difference TTG IgA U/mL , Mean ± SD 94.8 ± 61.7 1.8 ± 0.9 0.001 78.2 to 107.8 Ferritin (ng/mL), Mean ± SD 29.3 ± 14.7 52.9 ± 19.2 0.001 12.8 to 34.4 HbA1c % , Mean ± SD 8.4 ± 0.9 8.1 ± 1.3 0.435 0.5 to 1.1 Fasting Glucose (mg/dL), Mean ± SD 176.4 ± 30.0 149.7± 29.6 0.004 8.2 to 45.2 Figure 3: Comparison of TTG IgA Antibody Levels between CD Positive and CD Negative Groups Histological Findings All CD patients demonstrated villous atrophy (Marsh 3a-3c), with Marsh 3a (mild atrophy) being most common (41.7%), followed by Marsh 3b (moderate, 33.3%) and Marsh 3c (severe, 25.0%). No cases of milder inflammatory changes (Marsh 1, 2) were observed. Diagnostic Performance Table 5 Diagnostic Performance of TTG IgA Antibody Test Diagnostic Parameter Value 95% Confidence Interval Sensitivity 100.0% 73.5 - 100.0% Specificity 100.0% 95.9 - 100.0% Positive Predictive Value 100.0% 73.5- 100.0% Negative Predictive Value 100.0% 95.9 - 100.0% Area Under ROC Curve 1.000 (1.000, 1.000) Genetic and Temporal Associations Family history of celiac disease showed strong association with CD diagnosis 66.7% vs 0%, p<0.001 , representing one of the highest genetic clustering effects reported in literature. Peak CD prevalence occurred in patients with 11- 20 years of T1DM duration (22.7- 25.0%), with no cases in very short (≤5 years) or very long (20 years) diabetes duration.

This study establishes North West Rajasthan as a high-prevalence region for celiac disease in T1DM patients, with a biopsy-confirmed prevalence of 12.0%. This finding aligns closely with previous Indian studies by Bhadada et al. (11.1%) [12] and falls within the upper range of global estimates. The pronounced female predominance (6.3-fold increased risk) exceeds many reported gender ratios and may reflect population-specific genetic, hormonal, or environmental factors. The universal presence of villous atrophy in seropositive patients validates current diagnostic algorithms, while the perfect diagnostic performance of TTG IgA testing supports its reliability as a screening tool in this population. The predominance of atypical presentations, particularly iron-deficiency anemia 83.3% of CD patients, emphasizes that symptom-based case-finding approaches would miss the majority of cases. This finding reinforces the critical importance of active screening protocols in high-risk populations. The strong familial clustering 66.7% family history in CD patients substantially exceeds typical clustering rates of 10 - 20% in Western populations [10], possibly reflecting founder effects, consanguinity patterns, or concentrated HLA susceptibility alleles in this regional population. The temporal clustering with peak prevalence in intermediate diabetes duration (11-20 years) provides insights into natural disease history and supports periodic rather than one-time screening approaches. The absence of CD in patients with very short or very long diabetes duration may reflect insufficient time for autoimmune development or survivor bias effects. Study Limitations Hospital-based recruitment may have introduced selection bias toward more severe cases. The cross-sectional design precludes assessment of temporal causality beyond duration-based analysis. While the sample size was adequate for prevalence estimation, it limits precision of subgroup analyses. Clinical Implications These findings provide compelling evidence for implementing routine CD screening protocols in T1DM patients in North West Rajasthan. The 12% prevalence justifies resource allocation for systematic screening programs, while the excellent diagnostic performance of TTG IgA supports cost-effective screening strategies.

This comprehensive study establishes North West Rajasthan as a high-prevalence region for celiac disease in Type 1 Diabetes Mellitus patients, with a biopsy-confirmed prevalence of 12.0%. The pronounced female predominance 22.7% vs 3.6% , atypical presentations dominated by iron-deficiency anemia, strong genetic clustering, and temporal patterns provide specific guidance for implementing targeted screening strategies. The excellent diagnostic performance of TTG IgA testing and substantial disease burden documented support routine screening protocols as a clinical imperative. The predominantly atypical presentations emphasize that active screening is essential, as symptom-based approaches would miss the majority of cases. Implementation of systematic CD screening protocols in T1DM patients from North West Rajasthan is justified by the substantial disease burden and clinical impact demonstrated. These findings contribute significantly to regional epidemiological knowledge and provide the evidence base necessary for healthcare policy development and optimal patient care. Future research should focus on longitudinal studies to clarify temporal relationships, genetic studies to understand population-specific risk factors, and cost-effectiveness analyses to optimize screening strategies in resource-constrained settings. Funding: This research received no specific grant from any funding agency in the public, commercial, or not-for- profit sectors. Conflicts of Interest: The authors declare no conflicts of interest. Ethics Statement: The study was conducted in accordance with the Declaration of Helsinki and approved by the Institutional Ethics and Research Board of S.P. Medical College, Bikaner.

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