Saturday, October 13, 2007

Tuberculosis

Interesting question submitted from Nasia:

18 year old man migrated from Thailand in 2005. Father in 2004-2205 had active pulmonary TB, treated for six months with standard regimen and responded. Patient does not recall whether he had PPD done then or not and was not treated for LTBI. Now is asymptomatic but CXR done for other reasons was abnormal.chest CT shows 5 very small (largest is 2.5 mm) scattered nodules. sputum AFBs are negative including cultures. current PPD negative and quantiferon test negative as well. Physical exam unrevealing. would you treat for latent TB given exposure?

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Anonymous said...

The specificity of the Quantiferon test is well over 99% in latent Tb. He is systemically well and the advantage that you have with the Quantiferon In Tube is that you would know that he is not anergic as a reason for the negative response. (The problem with the skin test is that the lack of response might have indicated anergy, but the Quantiferon test controls for this).

The nodules and negative sputum do not suggest active Tb. QFT is about 80% sensitive in active Tb. He might have had exposure to Tb or some other infection to cause the nodules in the past, but the negative Quantiferon indicates that he does not need treatment.