Table 3.

Bivariate receiver operating characteristic (ROC) analysis of the study groups

		AUC	SE	Sig	CI (95%)		Cut‐ offa	Sensitivity	Specificity
					Lower Bound	Upper Bound
MCI vs. HS	MMSE	0.906	0.03	0.0001b	0.847	0.965	27.5	0.82	0.984
	25 (OH)D3	0.765	0.04	0.0001b	0.681	0.849	27.5	0.902	0.541
	1,25(OH)2 D3	0.5	0.05	1.000	0.396	0.604	—	—	—
Mild AD vs. HS	MMSE	0.993	0.01	0.0001b	0.979	1	27.5	1	0.984
	25 (OH)D3	0.815	0.04	0.0001b	0.736	0.895	25.5	0.927	0.574
	1,25(OH)2 D3	0.41	0.06	0.124	0.293	0.527	—	—	—
Moderate AD vs. HS	MMSE	1	0	0.0001b	1	1	22	1	1
	25 (OH)D3	0.812	0.04	0.0001b	0.725	0.899	27.5	0.943	0.541
	1,25(OH)2 D3	0.472	0.06	0.645	0.351	0.593	—	—	—
Severe AD vs. HS	MMSE	1	0	0.0001b	1	1	17	1	1
	25 (OH)D3	0.911	0.03	0.0001b	0.857	0.966	20.5	0.906	0.787
	1,25(OH)2 D3	0.493	0.07	0.913	0.367	0.62	—	—	—
Mild AD vs. Moderate AD	MMSE	1	0	0.0001b	1	1	20.5	1	1
	25 (OH)D3	0.494	0.07	0.929	0.363	0.626	—	—	—
	1,25(OH)2 D3	0.566	0.07	0.327	0.436	0.695	—	—	—
Severe AD vs. Mild AD	MMSE	1	0	0.0001b	0	0	15.5	1	1
	25 (OH)D3	0.661	0.06	0.019b	0.538	0.785	21.5	0.341	0.969
	1,25(OH)2 D3	0.566	0.07	0.333	0.433	0.7	—	—	—
Severe AD vs. Moderate AD	MMSE	1	0	0.0001b	1	1	10.5	1	1
	25 (OH)D3	0.675	0.07	0.014b	0.546	0.804	21.5	0.314	0.969
	1,25(OH)2 D3	0.515	0.07	0.836	0.374	0.655	—	—	—
Total AD vs. HS	MMSE	0.997	0.003	0.0001b	0.992	1	27.5	1	0.984
	25 (OH)D3	0.843	0.03	0.0001b	0.782	0.904	20.5	0.741	0.787
	1,25(OH)2 D3	0.455	0.05	0.327	0.366	0.543	—	—	—

AUC, area under the ROC curve; CI, confidence interval; SE, standard error of AUC.

^aCutoff values at which optimal balance of sensitivity and specificity can be obtained according to Youden's index; Youden's Index can be calculated as the sum of sensitivity plus specificity minus 1 for all possible cutoff points.

^bSig, significance of AUC.