OBJECTIVE: Autoimmune thyroid disease is the most common comorbid autoimmune condition seen in patients with type 1 diabetes. Screening of thyroid dysfunction by measurement of TSH and Anti-TPO antibodies are recommended by ISPAD guidelines 2018 at the diagnosis of diabetes and, thereafter, every second year in asymptomatic individuals. The aim of this study was to investigate the prevalence of thyroid dysfunction and autoimmune marker of type 1 diabetes mellitus patient in Dr. Soetomo Hospital using anti-TPO and TSH.
METHOD: This cross sectional study examined 30 children with type 1 diabetes mellitus in out-patient clinic of pediatric endocrinology division at Dr. Soetomo Hospital during April - Mei 2019. Sample for this study was blood serum. Quantitative anti TPO determined by ELISA with cut of 75 IU/ml as positive or negative result (range 0-3000 IU/ml). Normal range of TSH test is 0.7-5.7 mLU/L. Statistic method was descriptive analysis.
RESULT: The mean age of 30 children was 11 years (range 3-18 years), 53.3% were boy. The median of diabetes duration was 4 years (range 0-15). Seven out of 30 (23.3%) patients had positive antibodies (positive anti-TPO) with the highest titer was >3000 IU/ml. The basal thyroid stimulating hormone (TSH) was elevated in 2 subjects with highest anti TPO titer. Sensitivity of anti-TPO and TSH to evaluate thyroid function was 66%, specificity was 81%, positive predictive value was 28%, and negative predictive value was 95.6%. 
CONCLUSION: Although TSH screening is more sensitive to detect thyroid abnormalities, the presence of positive serum anti-TPO antibodies may be an earlier marker for thyroid disease, therefore, patient with positive antibodies should be monitored for serum TSH elevation at yearly interval.