Chronic venous leg ulcer (CVLU) arises as a chronic venous insufficiency complication and is a major cause of morbidity throughout the world. Our hypothesis is that the CVLU exudate composition is a biochemical representation of the wound clinical state. Then, Fourier Transform Infrared (FTIR) spectroscopy could be a useful and less-invasive technique to study the clinical state of the ulcer. For this, the aim of this work was to perform a spectral characterization of the exudate from CVLU using FTIR spectroscopy to identify potential healing markers. 45 exudate samples from CVLU, 95% of the strains isolated from CVLU in planktonic and biofilm phenotypes and other related biological samples such as human plasma, serum, urine, blood cells, urea, creatinine, glucose and albumin were studied by FTIR spectroscopy. According to the vibration frequency of biomolecules' (lipids, proteins, nucleic acids and carbohydrates) characteristic bonds in the infrared region, different spectral windows were selected and spectral areas of each window were measured. Besides, Savitzky-Golay second derivatives were obtained for all spectra and peaks from each standardized window were detected. FTIR spectroscopy allowed identification of sample types (exudate, plasma, serum, urine) as each one presents a unique relative composition and ratios range. Also, this technique could be useful to identify bacteria in the phenotypic-ulcer state and allows differentiation of whether bacteria are in the biofilm or planktonic form which is unlikely by conventional methods. In this work we found some spectral markers (areas, peaks) that allow identification of several parameters in the exudate such as (a) total cellularity, (b) inflammatory cell load, (c) bacterial load, (d) fibrin amount, and (e) inflammatory proteins. Because the measured areas or founded peaks are concentration-dependent this method could also serve to measure them. Therefore, FTIR spectroscopy could be useful to evaluate patient evolution as all these exudate parameters represent critical negative markers for wound healing.

BACKGROUND: Some authors claim that the clinical methods often employed to assess chronic venous leg ulcers (CVLU) are based on subjective interpretation. The treatments based on a subjective characterization could become a trial-and-error therapy, resulting in longer evolutions and high recurrence rates. PURPOSE: The aim of this work was to compare numeric parameters from acute and chronic venous leg ulcers to identify potential objective nonhealing parameters. METHODS: The study was performed with hospital outpatients from 2016 to 2019. Cohorts were established according to the ulcer evolution time. Data collected related to ulcer characteristics included exudate pH, lactate and glucose concentrations, temperatures, microbiology findings, and imaging study results. RESULTS: Approximately 83% of the examined ulcers were chronic. Seventy-one percent of CVLUs and 59% of the acute ulcers had a pH ≥8. A high variability was found for the concentration of glucose and lactate in exudates of both acute and chronic ulcers. Variations of temperatures of normal skin (ΔT1) and periulcer zone (ΔT2) in reference to the wound bed temperature with values above 1 could indicate the presence of an inflammatory process and be used as a new potential marker of inflammation. All the acute ulcers and 88% of CVLUs showed <80% of granulation tissue in the imaging study. Finally, more than 105 organisms per gram of tissuewere found in 100% of the analyzed samples. CONCLUSIONS: Whereas there were not significant differences among the clinical measured parameters between acute and chronic ulcers, further research on the use of objective measurable parameters is needed to establish cutoff points to differentiate the “chronic state” of an ulcer as a “nonhealing state” regardless of the evolution time. Also, the use of these easily obtainable and low-cost nonhealing parameters would be a new approach to accurately monitor this pathology.

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