Table 3.

ROC analysis of TI parameters in identifying GS score ≥ 2 at the bilateral knees. 

TI parameter	Knee aspect	Optimal cut-off#	Youden’s index	SN (%)	SP (%)	PPV (%)	NPV (%)	AUC (95% CI)
Right knee (identifying GS score ≥ 2)
T-min	Lateral	29.6	0.383	66.7	71.6	40.0	88.3	0.69 (0.58, 0.81)
T-max	Lateral	33.5	0.512	71.4	79.7	50.0	90.8	0.76 (0.65, 0.87)
T-avg	Lateral	31.2	0.425	85.7	56.8	36.0	93.3	0.71 (0.62, 0.81)
T-min	Anterior	29.7	0.417	71.4	70.3	40.5	89.7	0.71 (0.60, 0.82)
T-max	Anterior	33.4	0.403	71.4	68.9	39.5	89.5	0.70 (0.59, 0.81)
T-avg	Anterior	31.2	0.479	85.7	62.2	39.1	93.9	0.74 (0.65, 0.83)
T-min	Medial	29.1	0.302	66.7	63.5	34.1	87.0	0.65 (0.53, 0.77)
T-max	Medial	33.5	0.382	57.1	81.1	46.2	87.0	0.69 (0.57, 0.81)
T-avg	Medial	30.3	0.317	95.2	36.5	29.9	96.4	0.66 (0.59, 0.73)
Left knee (identifying GS score ≥ 2)
T-min	Lateral	29.7	0.566	73.7	82.9	51.9	92.6	0.78 (0.67, 0.89)
T-max	Lateral	33.7	0.434	68.4	75.0	40.6	90.5	0.72 (0.60, 0.84)
T-avg	Lateral	31.6	0.618	84.2	77.6	48.5	95.2	0.81 (0.71, 0.91)
T-min	Anterior	30.7	0.500	57.9	92.1	64.7	89.7	0.75 (0.63, 0.87)
T-max	Anterior	33.6	0.513	73.7	77.6	45.2	92.2	0.76 (0.64, 0.87)
T-avg	Anterior	31.5	0.632	84.2	78.9	50.0	95.2	0.82 (0.72, 0.91)
T-min	Medial	29.3	0.461	78.9	67.1	37.5	92.7	0.73 (0.62, 0.84)
T-max	Medial	34.1	0.461	52.6	93.4	66.7	88.8	0.73 (0.61, 0.85)
T-avg	Medial	31.2	0.632	84.2	78.9	50.0	95.2	0.82 (0.72, 0.91)

TI Thermal imaging, T-min Minimum temperature, T-max Maximum temperature, T-avg Average temperature, GS Grey-scale, SN Sensitivity, SP Specificity, PPV Positive predictive value, NPV Negative predictive value, AUC Area under the receiving operating characteristic curve. ^#Chosen based on Youden’s index.