Table 1.

Characteristics of included studies.

Author	Survey year	Province	Region	Age, year	Sample size	Boy, %	Population source	Specimen	Laboratory method
CHNS [20]	2009	9 Provincesa	South + North	3–19	907	54.7	Community	Serum	Enzymatic colorimetric
Bo et al. [10]	2010	Tianjin	North	7–17	1269	50.3	Community	Serum	Enzymatic colorimetric
Chen et al. [11]	2012	Hebei	North	4–15	999	56.0	Health examination centre	Serum	Enzymatic colorimetric
Liu et al. [12]	2013	Shanxi	North	8–14	809	52.8	School	Serum	Enzymatic colorimetric
Zhuang et al. [13]	2014	Heilongjiang	North	10–18	1640	49.8	Community	Serum	Enzymatic colorimetric
Li et al. [14]	2015	Tianjin	North	3–6	4073	52.5	Community	Serum	Enzymatic colorimetric
Zhang et al. [15]	2015	Nationwide	South + North	17–19	600	100	School	Serum	Enzymatic colorimetric
Lu et al. [16]	2017	Shandong	North	13–19	21,602	49.1	Community	Serum	Enzymatic colorimetric
Chen et al. [17]	2017	Zhejiang	South	3–19	10,764	61.6	Health examination centre	Serum	Enzymatic colorimetric
Wu et al. [18]	2018	Jiangsu	South	13–16	509	49.1	Community	Serum	Enzymatic colorimetric
Ye et al. [19]	2019	Beijing	North	6–16	11,408	49.9	School	Serum	Enzymatic colorimetric

^aIncluding Heilongjiang, Liaoning, Shandong, Jiangsu, Guangxi, Guizhou, Henan, Hubei and Hunan.