Q: I was suspected to have tuberculosis (TB) last year as I had two episodes of uveitis, which could be due to hypersensitivity reaction to tuberculosis bacilli. My chest X-ray was normal, but PPD was more than 10 mm and ESR was 52 mm. I was started on a nine-month-course of ATT as I was studying in a medical college. I took the whole course of ATT. Now this month, when I repeated the tuberculin test again, it came out more than 10 mm. What does this mean? Do I still have TB? What tests do I need to rule it out? If the repeat tuberculin test is false positive, then when will it become fully negative? I don't have any signs and symptoms of TB now.

A:A tuberculin test is a skin test done to check the presence of cell mediated immunity of an individual towards the tuberculoprotein (PPD). A positive test only indicates that the person has been exposed to Mycobacterium tuberculosis in the past and has developed cell mediated immunity. It is not a test to diagnose active tuberculosis. It remains positive for the entire life of an individual unless there is a deficiency of CMI. Most individuals in an endemic area like India are tuberculin test positive. It is highly unlikely that you are still suffering from tuberculosis, as you don’t have any symptoms.