Nitric oxide levels in wound fluid may reflect the healing trajectory.

We analyzed nitric oxide metabolites (nitrate and nitrite, NOx) and other biomarkers in human wound fluids and correlated these markers with wound healing status (progressing or worsening) based on patient's wound history. Samples were collected pre- and postcleansing from patients with wounds of various etiologies and analyzed for NOx, matrix metalloproteinase activity, and elastase activity. A laboratory method was developed to analyze NOx which can detect at least 5 μM in samples as small as 10 μL. A nitrate-free sample collection device was identified to match the sensitivity of this new assay (most "nitrate-free" products tested contained nitrate levels higher than this detection limit when extracted in such a small volume). The correlation between pre- and postcleansing biomarker values, and the diagnostic potential of the biomarkers to wound progress were analyzed. Fifty wounds provided samples that were suitable for NOx analysis. The pre- and postcleansing values for NOx showed good correlation (r = 0.72); the correlation was not very strong for matrix metalloproteinase and elastase. Data analysis showed that NOx represents the best metabolite to discriminate between worsening and progressing wounds, and suggested that a two cut point diagnostic test using NOx is better than a single cut point test to identify progressing from worsening wounds.