Vitamin D deficiency in HIV-infected patients: associated with non-nucleoside reverse transcriptase inhibitor or efavirenz use?

We read with interest recent articles by Mueller et al. [1] and Welz et al. [2] on the prevalence and factors associated with vitamin D deficiency in HIV-infected patients. As far as exposure to specific antiretroviral drugs are considered, Mueller et al. [1] demonstrated that non-nucleoside reverse transcriptase inhibitor (NNRTI) use is associated with 25-hydroxy-vitamin D [25(OH)D] deficiency. Welz et al. [2] demonstrated that the current use of efavirenz but not nevirapine is associated with severe 25(OH)D deficiency. Although the number of studies stating that NNRTI use is associated with vitamin D deficiency is growing it is unclear whether this association is related to NNRTI class or to efavirenz use [3, 4].