Development and validation of a tongue image-clinical nomogram for detection of advanced colorectal adenoma

Table 2 Threshold-based classification performance in the Asia-Pacific colorectal screening score ≥ 4 subgroup using training-derived cutoffs (specificity fixed at approximately 80%)

Method	Cohort	Threshold	TP	FP	TN	FN	Sensitivity (%)	Specificity (%)	PPV (%)	NPV (%)	Accuracy (%)
Tongue image-clinical nomogram	Training	0.5876	54	14	54	27	66.67	79.41	79.41	66.67	72.48
	Validation	0.5876	21	7	21	15	58.33	75.00	75.00	58.33	65.62
Tongue-only model	Training	0.6344	50	15	53	31	61.73	77.94	76.92	63.10	69.13
	Validation	0.6344	23	5	23	13	63.89	82.14	82.14	63.89	71.88
APCS score	Training	5	24	16	52	57	29.63	76.47	60.00	47.71	51.01
	Validation	5	7	5	23	29	19.44	82.14	58.33	44.23	46.88
M-APCS score	Training	5	21	14	54	60	25.93	79.41	60.00	47.37	50.34
	Validation	5	9	2	26	27	25.00	92.86	81.82	49.06	54.69

Cutoffs for each method were determined in the Asia-Pacific colorectal screening score ≥ 4 training subset to achieve approximately 80% specificity and were applied unchanged to the Asia-Pacific colorectal screening score ≥ 4 validation subset. Advanced adenoma was treated as the positive class and nonadvanced adenoma as the negative class. APCS: Asia-Pacific colorectal screening; M-APCS: Modified Asia-Pacific colorectal screening; TP: True positive; FP: False positive; TN: True negative; FN: False negative; PPV: Positive predictive value; NPV: Negative predictive value.