Table 2.

ROC analysis of TI parameters in identifying PD score>0 at the bilateral knees.

TI para- meter	Knee aspect	Optimal cut-off#	Youden’s index	SN (%)	SP (%)	PPV (%)	NPV (%)	AUC (95% CI)
Right knee (identifying PD score > 0)
T-min	Lateral	29.6	0.329	63.2	69.7	34.3	88.3	0.67 (0.54, 0.79)
T-max	Lateral	33.5	0.526	73.7	78.9	46.7	92.3	0.76 (0.65, 0.88)
T-avg	Lateral	31.2	0.395	84.2	55.3	32.0	93.3	0.70 (0.60, 0.80)
T-min	Anterior	29.7	0.434	73.7	69.7	37.8	91.4	0.72 (0.60, 0.83)
T-max	Anterior	33.5	0.368	63.2	73.7	37.5	88.9	0.68 (0.56, 0.81)
T-avg	Anterior	31.2	0.447	84.2	60.5	34.8	93.9	0.72 (0.62, 0.82)
T-min	Medial	29.1	0.250	63.2	61.8	29.3	87.0	0.63 (0.50, 0.75)
T-max	Medial	33.5	0.447	63.2	81.6	46.2	89.9	0.72 (0.60, 0.84)
T-avg	Medial	30.3	0.303	94.7	35.5	26.9	96.4	0.65 (0.58, 0.73)
Left knee (identifying PD score > 0)
T-min	Lateral	29.5	0.598	85.7	74.1	36.4	96.8	0.80 (0.69, 0.91)
T-max	Lateral	34.0	0.507	64.3	86.4	45.0	93.3	0.75 (0.62, 0.89)
T-avg	Lateral	31.6	0.598	85.7	74.1	36.4	96.8	0.80 (0.69, 0.91)
T-min	Anterior	30.7	0.460	57.1	88.9	47.1	92.3	0.73 (0.59, 0.87)
T-max	Anterior	33.6	0.539	78.6	75.3	35.5	95.3	0.77 (0.65, 0.89)
T-avg	Anterior	31.6	0.647	85.7	79.0	41.4	97.0	0.82 (0.72, 0.93)
T-min	Medial	29.3	0.511	85.7	65.4	30.0	96.4	0.76 (0.65, 0.86)
T-max	Medial	34.1	0.569	64.3	92.6	60.0	93.8	0.78 (0.65, 0.92)
T-avg	Medial	31.2	0.610	85.7	75.3	37.5	96.8	0.81 (0.70, 0.91)

TI Thermal imaging, T-min Minimum temperature, T-max Maximum temperature, T-avg Average temperature, PD Power Doppler, 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.