The use of oxygen as a possible screening biomarker for the diagnosis of chronic fatigue

Background: The aim of this study was to verify whether the mean percentage of oxygen use in the aerobic-anaerobic transition phase or isocapnic buffering (IB) was lower in women with chronic fatigue syndrome (CFS) compared to healthy women, and if this variable could be used as a screening biomarker for the diagnosis of CFS Methods: A cross-sectional study was conducted. Forty-four adult women (22 with CFS and 22 healthy) performed a cycle ergometer stress test with gas analyser (CPET). Maxi-mum oxygen consumption (_VO2 max), oxygen consumption at the anaerobic threshold (_VO2 at Vt2), maximum ventilatory volume ( _VE max), time of maintenance of the isocapnic buffering phase (IB duration), and mean percentage of oxygen use in isocapnic buffering phase (% O2 use in IB) were analyzed. Data were explored from a principal component analysis. Groups were matched by propensity score to be mismatched in BMI and a comparison of means and medians was performed. A logistic regression model was built to predict the probability of CFS. Results: The mean and median values of the variables obtained in the CPET was significantly higher in the healthy group compared to the CFS. In the logistic regression model, VO2 max, IB duration, and mean % of O2 use in IB were selected as predictors. The sensitivity and specificity were greater than 90%. Conclusion: The combination of the factors _VO2 max, IB duration, and mean % of O2 use in IB can be used as a screening biomarker for the diagnosis of CFS.(c) 2022 FUTBOL CLUB BARCELONA and CONSELL CATALA DE L'ESPORT. Published by Elsevier Espana, S.L.U. This is an open access article under the CC BY-NC license (http:// creativecommons.org/licenses/by-nc/4.0/).