Table 1.

Baseline characteristics of included studies

Study	Year of publication	Country	Patients	Nodules	Average age	Study design	Reference standard	Sensitivity	Specificity	PPV	NPV	ACC
Ko et al. [20]	2014	Korea	195	204	51	retrospective	Cytology and histology	0.985	0.158	0.354	0.957	0.422
Zhang et al. [21]	2015	China	2,921	3,980	51.6	prospective	Cytology, histology and US follow-up	0.974	0.91	0.396	0.998	0.913
Srinivas et al. [22]	2016	India	365	365	33.1	prospective	Cytology and histology	0.96	0.926	0.49	0.997	0.929
Yoon ATA et al. [24]	2016	Korea	1,241	1,293	50.8	retrospective	Cytology and histology	0.974	0.293	0.233	0.981	0.416
Sun et al. [25]	2017	China	1,293	388	49.5	retrospective	Cytology, histology, and US follow-up	0.987	0.307	0.473	0.973	0.57
Yoon et al. [23]	2016	Korea	4,585	4,696	50.9	retrospective	Cytology and histology	0.988	0.255	0.275	0.986	0.418

PPV positive predictive value, NPV negative predictive value, ACC diagnostic accuracy