Table 2. Heterogeneity assessment of the pooled studies.

Analysis	Spearman correlation Coefficient	Cochran's-Q test	I2 test (%)	Heterogeneity
				Threshold effect	Non-threshold effect
Overall	0.125a	51.46b	68.9	No	Yes
	P = 0.633	P = 0.0000
Plasma-based	0.400a	4.96b	39.6	No	No
	P = 0.600	P = 0.1745
Tissue-based	0.126a	43.66b	72.5	No	Yes
	P = 0.681	P = 0.0000

^aValue of spearman correlation coefficient

^bQ value