Mostafa Qorbani1, Armita Mahdavi Gorabi2, Hanieh-Sadat Ejtahed3, Nazli Namazi4, Maliheh Khoramdad5, Ramin Heshmat2, Elham Kazemian6, Roya Kelishadi7. 1. Non-communicable Diseases Research Center, Alborz University of Medical Sciences, Karaj, Iran; Chronic Diseases Research Center, Endocrinology and Metabolism Population Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran. 2. Chronic Diseases Research Center, Endocrinology and Metabolism Population Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran. 3. Endocrinology and Metabolism Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran; Obesity and Eating Habits Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran. 4. Diabetes Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran. 5. Department of Epidemiology, School of Public Health, Iran University of Medical Sciences, Tehran, Iran. 6. Non-communicable Diseases Research Center, Alborz University of Medical Sciences, Karaj, Iran. Electronic address: kazemianelham@yahoo.com. 7. Child Growth and Development Research Center, Research Institute for Primordial Prevention of Non-Communicable Disease, Isfahan University of Medical Sciences, Isfahan, Iran.
Abstract
OBJECTIVES: The reference values to determine vitamin A and D deficiency may vary based on ethnicity, age, and region of residence. The aim of this study was to determine the reference interval of circulating vitamin A and D levels among Iranian children and adolescents based on sex, age, and region of residence. METHODS: This nationwide cross-sectional study was performed with 2596 students 7 to 18 y of age from the CASPIAN-V (Childhood and Adolescence Surveillance and Prevention of Adult Non- communicable disease) study. A parametric method was used to define the age-specific reference values by obtaining smooth centile curves and explicit formulae for the centile estimates and SD scores for both sexes and regions of residence. RESULTS: Significant differences were found between the residents of rural and urban regions in terms of serum 25-hydroxyvitamin D [25(OH)D] and retinol concentration (P < 0.05). Boys (27 ± 8 versus 26.04 ± 10, P = 0.009). Children ages 7 to 12 y had higher serum 25(OH)D concentration than 13- to 18-y-old adolescents (26.96 ± 8 versus 26.04 ± 10, P = 0.007). The estimated reference interval for circulating 25(OH)D levels corresponding to the range between the 5th and 95th percentiles were 11.45 to 48.40 ng/mL in boys and 9.51 to 47.69 ng/mL in girls. Estimated reference intervals for serum retinol concentration among boys and girls corresponding to the 5th and 95th percentiles were 0.58 to 3.38 and 0.58 to 4.52, respectively. There were significant variations in both retinol and 25(OH)D concentrations across different age groups. CONCLUSION: This study established the reference intervals for circulating 25(OH)D and retinol levels in Iranian adolescents and children in different age groups based on sex and region.
OBJECTIVES: The reference values to determine vitamin A and Ddeficiency may vary based on ethnicity, age, and region of residence. The aim of this study was to determine the reference interval of circulating vitamin A and D levels among Iranian children and adolescents based on sex, age, and region of residence. METHODS: This nationwide cross-sectional study was performed with 2596 students 7 to 18 y of age from the CASPIAN-V (Childhood and Adolescence Surveillance and Prevention of Adult Non- communicable disease) study. A parametric method was used to define the age-specific reference values by obtaining smooth centile curves and explicit formulae for the centile estimates and SD scores for both sexes and regions of residence. RESULTS: Significant differences were found between the residents of rural and urban regions in terms of serum 25-hydroxyvitamin D [25(OH)D] and retinol concentration (P < 0.05). Boys (27 ± 8 versus 26.04 ± 10, P = 0.009). Children ages 7 to 12 y had higher serum 25(OH)D concentration than 13- to 18-y-old adolescents (26.96 ± 8 versus 26.04 ± 10, P = 0.007). The estimated reference interval for circulating 25(OH)D levels corresponding to the range between the 5th and 95th percentiles were 11.45 to 48.40 ng/mL in boys and 9.51 to 47.69 ng/mL in girls. Estimated reference intervals for serum retinol concentration among boys and girls corresponding to the 5th and 95th percentiles were 0.58 to 3.38 and 0.58 to 4.52, respectively. There were significant variations in both retinol and 25(OH)D concentrations across different age groups. CONCLUSION: This study established the reference intervals for circulating 25(OH)D and retinol levels in Iranian adolescents and children in different age groups based on sex and region.