Table 4.

Subgroup analysis of studies given countries or US methods, respectively.

		Statistics
	Number of studies	Sensitivity	Specificity	Asymmetric AUC (SE) of SROC	Risk ratio (95% CI) of sensitivity	Risk ratio (95% CI) of specificity
Western countries
M alone	5	0.67 (0.61–0.73)	0.89 (0.88–0.89)	0.643 (0.118)	0.693 (0.636–0.755)*	1.079 (1.001–1.164)*
M + US	5	0.93 (0.90–0.96)	0.78 (0.78–0.79)	0.982 (0.023)	Reference	Reference
M (–) → US	3	0.95 (0.98–0.99)	0.90 (0.89–0.90)	0.970 (0.041)	–
Far Eastern countries
M alone	2	0.88 (0.81–0.93)	0.97 (0.97–0.98)	N/A	0.706 (0.426–1.169)	1.015 (1.008–1.023)*
M + US	2	1.00 (0.97–1.00)	0.96 (0.95–0.96)	N/A	Reference	Reference
M (–) → US	3	1.00 (0.79–1.00)	0.79 (0.77–0.80)	0.950 (0.035)	–
ABUS
M alone	4	0.69 (0.62–0.75)	0.89 (0.88–0.89)	0.671 (0.120)	0.722 (0.673–0.774)*	1.05 (0.969–1.137)
M + US	4	0.93 (0.89–0.96)	0.79 (0.78–0.79)	0.987 (0.021)	Reference	Reference
M (–) → US	0	–
HHUS
M alone	3	0.81 (0.74–0.87)	0.97 (0.96–0.97)	0.961 (0)	0.665 (0.446–0.99)*	1.067 (1.029–1.106)*
M + US	3	0.99 (0.96–1.00)	0.94 (0.94–0.94)	0.972 (0.333)	Reference	Reference
M (–) → US	6	0.96 (0.91–0.99)	0.88 (0.87–0.88)	0.962 (0.02)	–
First-round US screening
M alone	2	0.72 (0.64–0.80)	0.87 (0.86–0.87)	N/A	0.683 (0.595–0.784)*	1.092 (0.930–1.284)
M + US	2	1.00 (0.97–1.00)	0.75 (0.74–0.75)	N/A	Rreference	Reference
M (–) → US	3	1.00 (0.71–1.00)	0.73 (0.71–0.75)	0.944 (0.039)	–

M mammogram, US ultrasound, ABUS automated breast US, HHUS handheld US, N/A not available, ROC receiver-operating characteristic, SROC summary ROC, CI confidence interval, AUC area under SROC, SE standard error.

*P value <0.05.