Analytical lights and shadows in metabolomics research on obstructive sleep apnea

index: Homeostatic model assessment for insulin resistance, LC–QTOF/MS: Liquid chromatography–quadrupole time of flight–mass spectrometry, LC–TOF/MS: Liquid chromatography– mass spectrometry, LC–MS/MS: Liquid chromatography coupled with tandem mass spectrometry, mRNA: Messenger RNA, NMR: Nuclear magnetic resonance, QCs: Quality controls, OA CEAS: Off axis cavity enhanced absorption spectroscopy, OSA: Obstructive sleep apnea (obstructive sleep apnoea), PLS–DA: partial least squares discriminant analysis, PSG: Polysomnography, ROC: Receiver–operator characteristic, SESI–MS: Secondary–electrospray–ionization–mass spectrometry, SIL–ISs: Stable isotopic labeled internal standards, TD–GC–MS: Thermal desorption gas chromatography mass spectrometry, TRP: Tryptophan, VOCs: Volatile organic compounds Abstract A critical opinion about how clinical researchers face to the metabolomics–obstructive sleep apnea (OSA) binomial is here presented from the point of view of analytical chemists. Thus, positive and negative (lights and shadows) aspects related to the types of samples used for the target studies, the pros and cons of the devices used for sampling and present storage conditions, and actions for their improvement are expressed. Sample preparation and its multiple facets that required to be clarified are discussed, as well as those related to analysis. A key aspect as data treatment has been discussed in the light of the cohorts handled to obtain the information to be subjected to appropriate/inappropriate treatment, and support on suitable examples has been provided. The search for OSA biomarkers, one of the areas to which key investigations are devoted at present, is critically discussed by showing the weak points and proposing new ways for improvement. A final section is devoted to aspects that may help to improve metabolomics–OSA research, a field asking for more attention.