Statistical methods

Stata version 18.0-Basic Edition (StataCorp LLC, TX, USA) was used for statistical analyses. Logistic regression was performed, and performance of the investigated Raman system in HS prediction was evaluated through serial binary classifications and corresponding Receiver Operating Characteristic (ROC) analyses. As a non-parametric test, the Mann-Whitney U test was a used to compare whether there is a significant difference in the distributions of two groups of samples after classification.