Table 1

Allele and genotype frequency of the 677C>T allele of the MTHFR gene by area and ethnic origin

		Genotype (No)*			Genotype (%)				Allele frequency
					CC	CT	TT		T
Area	Sample No	CC	CT	TT	(%)	(%)	(%)	95% CI	(%)
*TT, two 677C>T alleles; CT, one 677C>T allele; CC, no 677C>T allele.
Europe
Italy, Sicily	468	138	236	94	29	50	20.1	16.7 to 24.0	45.3
Italy, Campania	500	172	196	132	34	39	26.4	22.7 to 30.4	46.0
Italy, Veneto
Italian whites	385	128	198	59	33	51	15.3	12.1 to 19.3	41.0
Others	47	27	15	5	57	32	10.6	4.6 to 22.6	26.6
Spain, multicentre
Spanish whites	601	265	265	71	44	44	11.8	9.5 to 14.6	33.9
Others	51	24	20	7	47	39	13.7	6.8 to 25.7	33.3
France, Strasbourg	178	72	85	21	40	48	11.8	7.8 to 17.4	35.7
The Netherlands	188	97	79	12	52	42	6.4	3.7 to 10.9	27.4
Finland, Helsinki	545	293	230	22	54	42	4.0	2.7 to 6.0	25.1
Hungary	378	165	171	42	44	45	11.1	8.3 to 14.7	33.7
Russia	587	312	234	41	53	40	7.0	5.2 to 9.3	26.9
Middle East
Israel	210	120	72	18	57	34	8.6	5.5 to 13.1	25.7
China
North, Han ethnicity	643	201	315	127	31	49	19.8	16.9 to 23.0	44.2
South, Han ethnicity	430	167	228	35	39	53	8.1	5.9 to 11.1	34.7
Oceania
Australia
Whites	288	146	119	23	51	41	8.0	5.4 to 11.7	28.6
Others	75	40	27	8	53	36	10.7	5.5 to 19.7	28.7
Americas
Mexico	500	91	248	161	18	50	32.2	28.3 to 36.4	57.0
USA, Atlanta
Whites	300	142	126	32	47	42	10.7	7.7 to 14.7	31.7
Blacks	298	231	59	8	78	20	2.7	1.4 to 5.2	12.6
Hispanics	62	22	29	11	35	47	17.7	10.2 to 29.0	41.1
Asian	26	16	9	1	62	35	3.8	0.7 to 18.9	21.2
Other, unknown	100	63	32	5	63	32	5.0	2.2 to 11.2	21.0
Canada, Alberta
Whites	240	136	90	14	57	38	5.8	3.5 to 9.6	24.6
Others	30	17	13	0	57	43	0.0	0.0 to 11.4	21.7
Total	7130