Q: I am 30 years old and asymptomatic. My PPD tuberculin skin test was 35 mm but the QuantiFeron TB Gold test was negative and CXR was clear too. I had taken the BCG vaccination at birth. My ESR level is 75mm/hr. I'm confused and depressed because of these results. Do I have TB or can it develop later? I would really appreciate your help.

A:The context or the clinical indication for doing these tests is important. Was it part of a pre-employment health check up? Or were the tests done because of history of tuberculosis among close contacts? I would request you to think carefully if any of the following symptoms are/were recently present - fever, cough, haemoptysis (blood in sputum), weight loss or night sweats. It is likely, if the test results as described are correct, that he has latent tuberculosis as opposed to active TB. I would advise and inform him about the symptoms of TB, the possibility of latent TB and refer him to a chest physician for follow up CXR (chest X ray) at 3 months and 12 months. BCG does not provide 100% protection and the efficacy of BCG can wane with time. The possibility of TB cannot be completely excluded because of the limitations of CXR and QFT gold test. In one study as much as 22% of patients with pulmonary TB had a normal CXR, and the value of QFT gold tests in immunosuppressed patients has not been evaluated. Similarly ESR can be raised in a variety of different situations apart from TB. Finally, I would advise you not to look at test results in isolation. Test results are pieces of a big structure, which together with history, physical examination help to arrive at a diagnosis. An individual test result should not be used to make or rule out a specific diagnosis.