Reference values for serum nitric oxide metabolites in an adult population

ObjectivesTo determine reference values for serum nitric oxide metabolites (nitrite + nitrate = NOx) concentrations in adult subjects.Design and methodsSerum NOx concentration was measured, using the Griess method, in 694 non-smoking apparently healthy subjects, randomly selected from a population-based study. The International Federation of Clinical Chemistry guidelines and the robust method were used for determining reference values.ResultsThe 95% reference values for serum NOx concentration and serum NOx/creatinine ratio were 11.5 to 76.4 μmol/L and 0.111 to 0.729 in men and 10.1 to 65.6 μmol/L and 0.121 to 0.777 in women, respectively. With increasing body mass index, upper limits of serum NOx and the NOx/creatinine ratio increased in women and decreased in men. Serum NOx levels above upper limits predicted both diabetes and metabolic syndrome in women.ConclusionsThis study reports the first set of reference values for serum NOx concentration and NOx/creatinine ratio in a relatively large healthy non-smoking population.