Plasma nitrate concentrations in children with infectious and noninfectious diarrhea

Background: In patients with intact renal function and low dietary nitrate intake, plasma nitrate concentrations reflect endogenous nitric oxide produ ction and are shown to be increased during inflammatory processes. The aim of this study was to compare plasma nitrate concentrations and hence endoge nous nitric oxide production in children with infectious and noninfectious diarrhea and to determine whether plasma nitrate concentrations could serve as a discriminant test between acute and chronic diarrhea in children. Methods: Three groups of patients were identified: 14 patients with acute g astroenteritis, 13 patients with chronic noninfectious diarrhea, and 14 pat ients with no evidence of gastrointestinal pathology and no underlying infe ctious process, who served as control subjects. Plasma nitrate concentratio ns were determined spectrophotometrically using the Greiss reaction before reduction to nitrite with a copper-coated cadmium column. Results: Mean plasma nitrate concentrations were 405.3 mu mol/L +/- 281.6 m u mol/L (standard deviation) in patients with infectious diarrhea, 134.7 mu mol/L +/- 77.0 mu moI/L inpatients with chronic diarrhea, and 54.1 mu mol/ L +/- 20.1 mu mol/L in control subjects (F = 42.6, P < 0.0001; analysis of variance). Plasma nitrate concentrations were significantly higher in the i nfectious diarrhea group compared with the noninfectious diarrhea and contr ol groups (Student-Newman-Keuls test, P < 0.5). Conclusions: Although an optimal cutoff concentration cannot be defined, pl asma nitrate concentrations in excess of 300 mu mol/L, are suggestive of an infectious process whereas values less than 100 mu mol/L are indicative of noninfectious diarrhea.