Q: My 58 years old mother is believed to be suffering from tuberculosis of vertebra (L4, L5). The tuberculin test came positive and the doctor has started treating her for tuberculosis. Recently I learned that there is a test called FNAC which gives 100 percent diagnosis of TB. However, I have heard that once the patient has taken TB medicines for more than five days, FNAC test is inconclusive. Should we go for the test or not?

A:Tuberculin or Mantoux is an indirect evidence of TB infection. Fine needle aspiration (FNA) could be used for cytology (FNAC) or microbiology (microscopy, culture and/or molecular diagnosis) to provide direct evidence of infection. Most investigations in medicine are never 100% accurate, since a small number of cases could always be either missed or may be wrongly diagnosed. Please discuss the feasibility of aspiration and the prognosis with the treating doctor.