Positive Tuberculin and Quantiferon Gold test
Dr Ira Shah
Medical Sciences Department, Pediatric Oncall, Mumbai
Address for Correspondence: Dr Ira Shah, 1, B Saguna, 271, B St Francis Road, Vile Parle {W}, Mumbai 400056, India.
Clinical Problem :
A 7 years old boy presented with dry cough for 1 month which subsided since last one week. There is no fever, loss of appetite or loss of weight. There is contact with a neighbor who is suffering from tuberculosis. The physician did a mantoux test which was 23 x 20 mm. Chest X-Ray was normal and ESR was 5 mm at end of 1 hour. Quantiferon gold test was also positive.
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What is the diagnosis_?
Discussion :
This child is currently asymptomatic. His mantoux test is positive suggestive of delayed hypersensitivity reaction to tubercular protein. However, this could be due to BCG or due to past infection with TB or even atypical mycobacterial infection. It does not tell us whether child is infected with MTB recently. Thus, in this child we do not know whether he is recently infected with TB or had a past TB infection. Chances of developing active TB disease are highest in the first 2 years of acquiring TB infection and in children less than 5 years of age. Thus, prophylaxis is needed in children less than 5 years with latent TB or those who have acquired TB infection recently. To determine whether this child has acquired infection recently or in the past, one can do Interferon Gamma release assays {IGRAs} which are in-vitro tests that work of the same principle of Mantoux test except that they will be positive only with recent TB infection since they do not depend on memory cells. IGRAs are negative with past TB infection and will not be false positive due to BCG. This child has both Mantoux tests and Quantiferon gold test positive suggestive of recent latent TB infection {LTBI}.
E-published: April 2012 Vol 9 Issue 4 Art No. 26
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