Major depressive disorder (MDD) is a socially detrimental psychiatric disorder, contributing to increased healthcare expenditures and suicide rates. However, no empirical laboratory-based tests are available to support the diagnosis of MDD. In this study, a NMR-based plasma metabonomic method for the diagnosis of MDD was tested. Proton nuclear magnetic resonance ((1)H NMR) spectra of plasma sampled from first-episode drug-naı̈ve depressed patients (n = 58) and healthy controls (n = 42) were recorded and analyzed by orthogonal partial least-squares discriminant analysis (OPLS-DA). The OPLS-DA score plots of the spectra demonstrated that the depressed patient group was significantly distinguishable from the healthy control group. Moreover, the method accurately diagnosed blinded samples (n = 26) in an independent replication cohort with a sensitivity and specificity of 92.8% and 83.3%, respectively. Taken together, NMR-based plasma metabonomics may offer an accurate empirical laboratory-based method applicable to the diagnosis of MDD.

Background: The purpose of our study was to evaluate the effect of 6% desflurane on short-term olfactory memory after laparoscopic surgery, and to investigate whether plasma concentrations of plasma S-100β protein, neuron specific enolase (NSE) and melatonin correlate with it.Methods: We collected medical data of patients who underwent laparoscopic surgery in the Second People's Hospital of Guiyang during May 2018 - February 2020. A total of 40 patients, who were aged 18-60 years old with American Society of Anesthesiologists (ASA) physical status I-II, were enrolled in the study. During the operation, the patients inhaled 6% desflurane to maintain the anesthesia. Patients were brought to the recovery room 45 minutes prior to the surgery (T0). And the patients were sent to the post-anesthesia care unit (PACU) after the surgery, if their Aldrete score was ≥ 9 points (T1), the CCCRC test was repeated to re-assess their olfactory memory. Venous blood samples (3 mL) were collected at T0 and T1, and the plasma was centrifuged at 3,000 rpm and then stored in a refrigerator at -20°C. Plasma S-100β protein, NSE, and melatonin levels were determined using ELISA.Results: There was no statistically significant difference in the odor identification score between T0 and T1 (P > 0.05). As compared with T0, the plasma concentrations of S-100β protein and NSE declined at T1. However, these differences were not statistically significant (P > 0.05). There were also no statistically significant changes in melatonin levels between T0 and T1 (P > 0.05）.Conclusions: This study found that undergoing general anesthesia with the inhaled anesthetic desflurane did not affect the short-term olfactory memory of patients undergoing laparoscopic surgery. This may be explained by the proposition that desflurane maintains plasma S-100β protein, NSE, and melatonin levels.Trial registration: Chinese Clinical Trial Registry (URL: http:// www.chictr.org.cn. Registry number: ChiCTR2100049441 ). Date of Registration: 2 August 2021.