Table 2. Subgroup analysis of diagnostic accuracy of CTCs.

Variables	SEN (95% CI)	SEP (95% CI)	PLR (95% CI)	NLR (95% CI)	DOR (95% CI)	AUC
Overall	0.34 (0.27, 0.42)I2 = 89.19	0.97 (0.93, 0.99)I2 = 89.71	11.8 (4.7, 29.5)I2 = 72.39	0.68 (0.60, 0.76)I2 = 78.58	17 (7, 46)I2 = 100	0.70 (0.66, 0.74)
Geographical location
American	0.38 (0.21, 0.59)I2 = 89.32	0.85 (0.62, 0.95) I2 = 86.68	2.5 (0.9, 7.0)I2 = 80.05	0.73 (0.52, 1.02)I2 = 79.85	3 (1, 13)I2 = 99.98	0.65 (0.61, 0.69)
European	0.35 (0.26, 0.46)I2 = 91.08	0.98 (0.92, 0.99)I2 = 91.59	14.5 (4.4, 47.5)I2 = 61.66	0.66 (0.57, 0.78)I2 = 82.16	22 (6, 76)I2 = 99.04	0.74 (0.70, 0.78)
Asian	0.28 (0.22, 0.35)I2 = 55.31	0.99 (0.75, 1.00)I2 = 38.37	33.6 (0.9, 1307.1)I2 = 0	0.72 (0.66, 0.79)I2 = 35.06	46 (1, 1870)I2 = 91.58	0.46 (0.42, 0.50)
Control type
Healthy	0.41 (0.29, 0.53)I2 = 90.20	0.99 (0.94, 1.00)I2 = 93.32	44.3 (6.8, 290.7)I2 = 69.57	0.60 (0.49, 0.73)I2 = 84.09	74 (11, 492)I2 = 99.71	0.79 (0.76, 0.83)
Mixed	0.30 (0.21, 0.39)I2 = 86.49	0.93 (0.84, 0.97) I2 = 83.34	4.0 (1.8, 9.0)I2 = 64.04	0.76 (0.67, 0.87)I2 = 69.49	5 (2, 13)I2 = 99.87	0.61 (0.57, 0.66)
Method
Immunology-based assay	0.48 (0.23, 0.74)I2 = 90.19	0.98 (0.91, 0.99)I2 = 0	20.6 (5.2, 81.8)I2 = 0	0.54 (0.31, 0.91)I2 = 84.44	38 (8, 192)I2 = 99.12	0.97 (0.95, 0.98)
PCR-based assay	0.32 (0.26, 0.40)I2 = 89.32	0.96 (0.90, 0.98)I2 = 90.07	7.5 (3.1, 18.0)I2 = 64.81	0.71 (0.64, 0.78)I2 = 72.47	11 (4, 27)I2 = 99.93	0.61 (0.57, 0.65)
Sample size
< 100	0.37 (0.28, 0.46)I2 = 85.07	0.99 (0.94, 1.00)I2 = 91.99	27.5 (5.6, 134.3)I2 = 77.31	0.64 (0.56, 0.74)I2 = 76.34	43 (8, 217)I2 = 100	0.70 (0.66, 0.74)
≥ 100	0.27 (0.18, 0.38)I2 = 95.20	0.93 (0.85, 0.97)I2 = 81.49	3.7 (2.2, 6.1)I2 = 53.76	0.79 (0.71, 0.88)I2 = 75.61	5 (3, 8)I2 = 99.87	0.68 (0.63, 0.72)

SEN: Sensitivity; SEP: Specificity; PLR: Positive Likelihood Ratio; NLR: Negative Likelihood Ratio; DOR: Diagnostic Odds Ratio; AUC: Area Under the sROC Curve.