The risk of perchlorate and iodine on the incidence of thyroid tumors and nodular goiter: a case-control study in southeastern China

Table 2 Differences of perchlorate, iodine levels in urine between control and case group

Variables	Pathological type	Overall participants		Controls		Cases		P-value ^a	P-value ^b
Variables	Pathological type	Median	25th-75th percentiles	Median	25th-75th percentiles	Median	25th-75th percentiles	P-value ^a	P-value ^b
Perchlorate (μg/L)		11.27	6.89-18.49
	Total cases			9.29	6.35-14.74	14.31	8.25-20.58	< 0.001	–
	NG			9.68	6.48-15.22	14.56	7.88-22.18	0.037	0.998
	PTMC			9.95	6.88-14.70	14.13	7.56-21.64	0.061
	PTC			8.73	5.75-13.39	14.27	8.67-19.16	0.002
Iodine (μg/L)		131.23	84.00-197.84
	Total cases			131.59	82.13-183.25	131.23	84.46-214.92	0.153	–
	NG			122.67	66.63-171.41	130.19	79.60-205.02	0.165	0.836
	PTMC			138.58	100.43-181.96	148.34	95.15-213.52	0.589
	PTC			130.35	84.74-189.80	126.97	88.82-215.71	0.697

Note: Data are presented as medians and 25–75 percentiles. Perchlorate and iodine were corrected by urinary specific gravity (USG). NG nodular goiter, PTMC papillary thyroid micro carcinoma, PTC papillary thyroid carcinoma, Total cases including NG, PTMC and PTC
^a P-value were derived from Wilcoxon signed-rank test between the case and control group
^b P-value was derived from the Kruskal-Wallis test between the three types of pathological

ISSN: 1476-069X