Reference values for serum nitric oxide metabolites in pediatrics.

Serum concentration of nitric oxide metabolites (NO(x)) is associated with cardiovascular disease risk factors in pediatrics. The aim of this study was to determine sex- and age-specific reference ranges for serum NO(x) concentrations in pediatrics. Serum NO(x) levels were measured in 401 subjects (189 boys and 212 girls), aged 4-19 years, using the Griess method. Study subjects selected from participants of Tehran lipid and glucose study, an ongoing cohort study aimed at determining of noncommunicable disease risk factors among Tehranian subjects. The International Federation of Clinical Chemistry guidelines and the robust method were used for determining reference values for sample sizes greater or less than 120 respectively. The 95% reference values for serum NO(x) concentrations were 13.6-69.2, 11.4-66.0, and 12.2-69.4 μmol/L in boys, girls, and total population respectively. The upper limit of serum NO(x) was 28% lower in otherwise healthy overweight and obese boys while it was 6% higher in overweight and obese girls, for both groups compared to their corresponding normal weight subjects. In conclusion, this study, for the first time, reports reference values for serum NO(x) levels in healthy children and adolescents.