Investigations and Management
- HIV test
- CXR - Tuberculosis is difficult to diagnose with certainty from a chest X-ray alone.
- Mantoux test if purified protein derivative (PPD) is available.
- Children do not expectorate well but if they can collect sputum/induced sputum for
microscopy for AFB (Acid Fast Bacilli), Gene Xpert (and Culture if available)
- Gastric aspirate for microscopy, culture and/or gene Xpert.
Ideally done in the very morning before breakfast after a night of starving (if a patient
on three hourly feeds, do before the next feed). Insert an NGT and aspirate gastric
content.
Collect it into a CSF bottle and send to laboratory.
Gene Xpert can also be done on other body fluids, sensitivity varies.
CXR
- changes compatible with PTB in >70% cases
Chest x-rays need to be of decent quality and interpretation depends on the expertise of the
person reading them. CXR changes are often non-specific and may be completely normal in
the HIV-infected or malnourished child.TB disease should not be diagnosed from the
CXR alone. The whole clinical picture should be considered.
The most common x-ray findings suggesting TB in children are:
- Enlarged hilar lymph nodes as evidenced by splaying of the right and left mainstream
bronchi) and/or a widened mediastinum due to enlarged lymph nodes (this is the most
common x-ray abnormality in children with TB).
- Unilateral infiltration on x-ray may indicate lobar disease.
- Diffuse uniformly distributed small miliary shadows.
- One-sided pleural effusions usually occur in children > 5 years
Mantoux procedure
(depending on the availability of PPD)
- The Mantoux test measures the delayed-type hypersensitivity response to purified
protein derivative (PPD)-a mixture of inactivated mycobacterial proteins.
- A positive Mantoux does not indicate active TB disease, it only indicates latent infection
with M. tuberculosis (LTBI).
- Intradermal injection of 2 tuberculin units (TU) of PPD RT23. Usually completed on the
left forearm
- The Mantoux test is positive when the diameter of skin induration (swelling, not
redness) is > 10 mm (or > 5 mm in an HIV-infected or malnourished child).
- Transverse induration measured 48-72hrs later using a tape measure and the ball-point
pen technique
- Result MUST be documented in mm and not just as 'positive' or 'negative'
- A negative TST does not exclude TB infection or disease