Fig. 1. SERS average spectra and different spectra of joint fluid from arthritis patients(n=18) and normal people(n=15)

Fig. 2. Posterior probability and ROC curves.(a) Posterior probability scatter of SERS spectra of joint fluid from arthritis patients and normal people based on PCA-LDA analysis and cross-validation method; (b) ROC curves under different identification thresholds

Fig. 3. Three-dimensional scatter plot of SERS spectra of joint fluid from arthritis patients (dot) and normal people (pentagram) based on PCA-LDA analysis and cross-validation method