Reference values for serum nitric oxide metabolites in an adult population

Objectives: To determine reference values for serum nitric oxide metabolites (nitrite+nitrate=NOx) concentrations in adult subjects. Design and methods: Serum 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. Results: The 95% reference values for serum NOx concentration and serum NOx/creatinine ratio were 11.5 to 76.4 mu mol/L and 0.111 to 0.729 in men and 10.1 to 65.6 mu mol/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. Conclusions: This study reports the first set of reference values for serum NOx concentration and NOx/creatinine ratio in a relatively large healthy non-smoking population. (c) 2009 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.