Percentile values of serum zinc concentration and prevalence of its deficiency in Iranian children and adolescents: the CASPIAN-V study

Background To determine the prevalence of serum zinc deficiency and provide the age- and sex-specific percentile values of serum zinc in children and adolescents. Methods We used the gathered data through the CASPIAN-V study, a national survey conducted on 3500 students aged 7-18 years from 30 provinces of Iran. In this study, 1370 blood samples were selected randomly, and serum zinc concentration was measured using a Hitachi automated analyzer. Zinc deficiency was defined as a serum zinc level of less than 75 μg/dL. Age-sex specific reference percentile values were developed for serum zinc concentration. Results The mean age of participants was 12.4 ± 3.0 years; 49.3% were girls and 73% were urban inhabitants. Mean (standard deviation [SD]) of serum zinc concentration was 107.23 (25.81) μg/dL with a significant sex difference; 109.03 ± 26.12 μg/dL for males compared to 105.41 ± 25.3 μg/dL for females (p = 0.009). The prevalence of subclinical zinc deficiency was 4.9% (95% confidence intervals [CI]: 3.0, 6.9) in children and adolescents. Both zinc deficient and sufficient groups were similar in terms of age, sex and residential areas (all p-value > 0.05). Overall, the 5th and 95th percentile values for serum zinc were 68.28 and 151.87 μg/dL, respectively. The value of all percentiles consistently decreased with age. The 10-99th percentile values for serum zinc were greater in boys than girls at all ages. Conclusions Nearly 5% of subjects had zinc deficiency. Age-sex specific percentile values were established for Iranian children and adolescents.