The University of Missouri Health Care System is re-evaluating its current policy on healthcare workers with latent tuberculous infection, which currently encourages but does not mandate treatment. The impetus for the review is a healthcare worker who had tested positive for latent tuberculosis via positive skin testing many years ago but declined to be treated, and recently developed active disease, exposing over 200 persons to tuberculosis. I suspect that most hospitals have similar policies and am not aware of a hospital that either prohibits those with latent but untreated infection from working or mandates treatment of latent tuberculosis. By definition, latent tuberculosis is not contagious but every person with latent infection has a small chance of developing active infection, which is contagious.
Isoniazid (INH), the standard drug used to treat latent tuberculosis given daily for nine months, is not an innocuous drug. In just the past few years, I have seen two deaths (both persons in their early 40s) and another healthy man who required a liver transplant due to the liver toxicity caused by the drug. Thus, I believe the drug is too toxic to require latently infected healthcare workers to be treated. Like the vast majority of healthcare workers, I have a TB skin test placed yearly. But I have decided that should my skin test convert to positive, I would not take INH because I believe it is too dangerous. We sorely need safer drugs for this condition. And we need better tests to detect latent tuberculosis--those currently available have many false positives and false negatives.