Table 2. Distribution of −509C/T genotypes and allele frequencies among DR of cases and controls, and P-values of HWE in cases and controls.

First Auther	Number		Cases(N)			HWE	Controls(N)			HWE	C Allele(N)
	case group	control group	CC	CT	TT	(p*value) for case group	CC	CT	TT	(p*value) for control group	case group	control group
Beránek M [7]	73	172	44	24	5	0.49	79	80	13	0.23	112	238
Buraczynska M [8]	195	168	79	85	31	0.31	40	44	16	0.51	243	124
Paine SK [9]	253	240	172	70	11	0.27	153	73	14	0.19	414	379

Abbreviations: DR: diabetic retinopathy; HWE: Hardy–Weinberg equilibrium.