Latent tuberculosis seems not to reactivate in multiple sclerosis patients on natalizumab.

Current safety recommendations for multiple sclerosis (MS) patients who are considered for natalizumab do not specify how to screen for latent tuberculosis (LTB). Only chest X-ray is recommended as a routine, and follow-up depends on its results. The incidence of TB in Spain is high and the risk of a LTB reactivation due to natalizumab is unknown. Our objective is to describe in our clinical practice if following the current recommendations for the MS population on natalizumab allows identifying patients with a LTB, as well as the risk for TB reactivation. Our study demonstrated that, in our environment, current recommendations are not sensitive enough to identify cases of LTB, though no cases of active TB were observed. Considering the lack of documented active TB cases worldwide among natalizumab patients, we suggest that these safety measures are probably unnecessary, even in countries with a high TB incidence.