Free and total vitamin D in psoriatic patients treated with biological drugs

Data regarding the association between psoriasis and vitamin D lev- els are controversial, may be due to the choice of dosing serum total 25(OH)D in order to assess the vitamin D nutritional state both at its basal levels and after supplementation. In the present study, we used the direct immunometric mea- surement of the levels of free 25(OH)D as a biomarker of the basal vitamin D status. In our study, the low free vitamin D levels reg- istered in psoriatic patients support the evidences of the pleiotropic effect of vitamin D and its likely pathogenetic role in psoriasis. Lower levels of the free fraction of vitamin D in psoriatic patients could be at least partially responsible for the altered control of kera- tinocytes proliferation and differentiation, as well as for the modu- lation of the inflammatory and immune processes. In conclusion, our study demonstrates that free 25(OH)D levels, measured with an ac- curate direct analytic method, can be a useful biomarker of vitamin D status in psoriatic patients treated with biological drugs.