ApaI, BsmI, FokI and TaqI polymorphisms in the vitamin D receptor (VDR) gene and the risk of psoriasis: a meta-analysis

Objectives To determine whether ApaI, BsmI, FokI or TaqI polymorphisms in vitamin D receptor (VDR) gene confer susceptibility to psoriasis. Methods All related association studies published before January 2012 were retrieved and eligible ones were included in our meta-analysis. For each of the four polymorphisms, we explored the significance of the associations for the allele contrast as well as the recessive and dominant models in overall samples, Caucasians and East Asians. Heterogeneity was identified by sensitivity analysis and publication bias was examined by funnel plot and Egger's test. Results 12 studies that met our selection criteria were included. For ApaI polymorphism, the dominant model for allele a in Caucasians produced a significant result [heterogeneity 2=3.46, P=0.177, I2=42.2%; ORfixed-effect model=1.398 (1.0111.934), z=2.03, P=0.043]. While in East Asians, pooling analysis under any genetic model acquired no-significant result. Significant heterogeneity was identified among East Asian studies and a Korean study accounted mostly for the heterogeneity detected. The heterogeneities were no longer statistically significant after removing this study, and the results of re-analyses in remaining studies have not been affected. Regarding TaqI polymorphism, the allele contrast discovered significant association between allele T and psoriasis susceptibility in Caucasians [heterogeneity 2=4.35, P=0.226, I2=31.1%; ORfixed-effect model=1.287 (1.0671.551), z=2.64, P=0.008]. As for the BsmI and FokI polymorphisms, allele contrast, recessive and dominant models produced non-significant results in either Caucasians or East Asians. The funnel plots and Egger's tests found no publication bias presenting in the studies analyzed. Conclusions This meta-analysis showed that ApaI, TaqI polymorphisms in VDR gene correlate with psoriasis in Caucasians.