Lee YH, et al. - Researchers assessed the association between circulating 25-hydroxy vitamin D (25(OH)D) levels and psoriasis, and determined the correlation between serum/plasma 25(OH)D levels and psoriasis severity. Findings suggested that in patients with psoriasis, circulating 25(OH)D levels were lower. Authors noted that between 25(OH)D levels and psoriasis severity, a small but statistically significant negative correlation existed. Significantly lower level of 25(OH)D in the psoriasis group for large but not for small sample sizes was revealed on subgroup analysis by sample size. A significantly lower 25(OH)D level was revealed on stratification by adjustment for age and/or sex or sample type in the psoriasis group after adjustment for serum but not after nonadjustment for plasma.