Ultrasound evaluation of thyroid size: a large nationwide study of schoolchildren in India.

ABSTRACT

BACKGROUND: Ultrasound assessment of thyroid volume is considered a more objective method than clinical palpation for the diagnosis of goitre. We used ultrasonography to establish normal reference cut-off points of thyroid volume in schoolchildren of different socioecomonic groups in India and compared the results with international norms. METHODS: In a cross-sectional study, we clinically examined 27,250 children from the lower and higher socioeconomic strata (SES) from all over India to determine their goitre staging. A single sonologist, using ultrasonography, assessed the thyroid volume in a subset of 15,986 children (8463 from the lower and 7523 from the higher SES). Students were recruited from at least one school each representing the higher and the lower SES, from cities located in 5 zones of India. Children with known thyroid disorders were excluded from the study. RESULTS: Clinical evaluation revealed a mean goitre prevalence of 19.9% (23.2% in girls; 16.5% in boys; 17.1% in the higher SES; 23.5% in the lower SES). The thyroid volume as assessed by ultrasonography was significantly higher in children from the lower SES (mean 5.65 ml, SE 0.02) compared with those from the higher SES (mean 5.02 ml, SE 0.02) after adjusting for the imbalance in body surface area (p < 0.001). Using international norms (WHO 2004), the prevalence of goitre in various body surface area categories among children who had no goitre on clinical examination ranged from 48.2% to 75.1% for boys and 23.2% to 67.4% for girls. CONCLUSION: The striking discrepancy in the prevalence of goitre assessed by using clinical examination and ultrasound techniques suggests that the norms recommended by WHO based on ultrasound techniques are not appropriate for India.