Table 2.

Median and quartiles for UIC by subgroup and P value for test of homogeneity across subgroups.

Variable	Values taken	(Percent)	Median	Percentile 25	Percentile 75	P value
Parity	Primiparas	(40%)	85	41	175	0.736
	Multiparas	(60%)	80	41	161
Education	School certificate	(25%)	105	52	231	0.002
	Higher school certificate	(27%)	64	33	117
	Tertiary	(48%)	86	42	166
Ethnicity	Australian	(79.3%)	78	41	156	0.582
	European	(3.5%)	81	39	178
	Asian	(2.5%)	80	44	185
	Filipino	(1.1%)	94	41	177
	Other	(12.3%)	114	56	180
History of thyroid disease	Familial and patient	(2.2%)	91	51	183	0.351
	Familial	(14.9%)	90	43	226
	Patient	(3.3%)	106	72	244
	Nil	(79.6%)	79	39	156
Vitamin supplements	Nil	(28.3%)	69	38	136	<0.001
	Elevit	(31.9%)	71	39	120
	Fefol	(0.3%)	32	32	32
	Blackmores (iodine 150 μg)	(27.8%)	123	61	226
	Fabfol (iodine 150 μg)	(4.7%)	60	31	78
	Other	(6.9%)	123	59	260
Vitamin supplement containing iodine	No	(67.5%)	72	39	141	0.001
	Yes	(32.5%)	115	48	213
Iodised salt	No	(78.6%)	81	39	162	0.396
	Yes	(21.4%)	81	47	185
Milk (grouped)	Nil	(13.0%)	71	39	180	0.035
	<1 serve/day	(23.8%)	77	31	126
	1 serve/day	(42.3%)	75	45	155
	>1 serve/day	(21.0%)	105	59	208
Dairy (grouped)	Nil	(19.1%)	101	47	273	0.078
	<1 serve/day	(22.2%)	76	41	154
	1 serve/day	(40.7%)	78	34	149
	>1 serve/day	(18.0%)	87	42	129
Fish (grouped)	Nil	(29.8%)	72	41	159	0.764
	<1 serve/day	(15.2%)	83	51	120
	1 serve/day	(39.1%)	89	38	193
	>1 serve/day	(16.0%)	87	47	179
Overall		N = 367	81	41	169