Table 2

Predictive value of evaluated indices of the ROC analysis for β-thalassaemia

HbA₂ (%)	TP	FN	FP	TN	LRP	NRP	Sn	Sp	YI
3.5	547	147	19	10	1.03	0.53	96.64	6.37	0.03
3.6	540	85	26	72	1.76	0.10	95.41	45.86	0.41
3.7	531	49	35	108	3.01	0.09	93.82	68.79	0.63
3.8	512	35	54	122	4.06	0.12	90.46	77.71	0.68
3.9	497	25	69	132	5.52	0.14	87.81	84.08	0.72
4.0	482	16	84	141	8.34	0.17	85.16	89.81	0.75
4.1	473	15	93	142	8.78	0.18	83.57	90.45	0.74
4.2	466	13	100	144	9.94	0.19	82.33	91.72	0.74
4.3	456	13	110	144	9.73	0.21	80.57	91.72	0.73
4.4	449	12	117	145	10.38	0.22	79.33	92.36	0.72
4.5	445	12	121	145	10.29	0.23	78.62	92.36	0.71

Likelihood ratio positive (LRP): sensitivity ÷ (1−specificity); likelihood ratio negative (NRP): (1−sensitivity)/specificity. Youden's Index (YI), sensitivity (Sn): true positive ÷ (true positive+false negative); specificity (Sp): true negative ÷ (true negative+false positive).
FN, false negative; FP, false positive; TN, true negative; TP, true positive.
Bold signifies HbA2 at the cut-off value of 4.0% yielded high values (0.898, 95% CI 0.874 to 0.919) for AUC and YI.