Table 4.

Youden Indices of biomarker sets for the diagnosis of OA.

Model	Threshold based on optimal Youden’s index in training dataset	Sensitivity in testing dataset using training dataset threshold [95% CIs]	Specificity in testing dataset using training dataset threshold [95% CIs]
BMI	0.82	0.52 (0.46,0.59)	0.60 (0.54,0.66)
BMI, age, sex	0.85	0.42 (0.36,0.49)	0.82 (0.77,0.87)
ACTG	0.8	0.71 (0.66,0.77)	0.62 (0.56,0.68)
ACTG + BMI	0.73	0.71 (0.65,0.77)	0.67 (0.61,0.73)
23 RF peptides	0.86	0.81 (0.75,0.86)	0.82 (0.77,0.87)
23 RF peptides + BMI	0.81	0.86 (0.81,0.9)	0.76 (0.7,0.81)
17 uncorrelated peptides	0.83	0.77 (0.72,0.83)	0.84 (0.8,0.89)
17 uncorrelated peptides + BMI	0.79	0.88 (0.83,0.92)	0.73 (0.68,0.79)
8 significant peptides	0.81	0.78 (0.73,0.84)	0.78 (0.72,0.83)
8 significant peptides + BMI	0.9	0.94 (0.91,0.97)	0.69 (0.63,0.75)

For the list of the peptides in each set see Table 2; see Table S3 for the beta estimates for the models of demographics, Table S4 for models of the 23 RF peptides +/− BMI, Table S5 for models of the 17 uncorrelated peptides +/− BMI, and Table S6 for models of the 8 significant peptides +/− BMI