Diagnostic pathway for TB in children

Initial assessment - all children

To exclude signs and symptoms of active TB disease and to determine if the child needs to be commenced on full treatment, or chemoprophylaxis with INH.

History

• Document who referred and the reason for referral
• Has the child been treated with recurrent courses of antibiotics?
• Has the child been vaccinated with BCG? Check passport and scar.

Symptoms to ask about (Note symptoms may be non-specific)

• A chronic cough that is getting worse, especially if it has not responded to antibiotics
• Failed to gain weight or has lost weight for more than 4 weeks (a weight chart is valuable)
• Decrease in energy levels
• Low-grade fever for more than a week without any explanation
• Chronic diarrhoea with large pale stools, which has not responded to treatment for worms or giardiasis
• A headache and irritability, occasional vomiting, child wishes to be left alone and gradually becomes less rousable over 2-3 weeks

Contact History

• Who is the contact? Household member/neighbour?
• What has been the duration and proximity of contact? E.g.: Sleeping same room/ same bed?

General

• Full systems review
• HIV status?

PM History

• Is there a history of asthma, wheeze, chronic cough?
• Regular medicines? BCG vaccination?

Examination

• Temp, Pulse, RR
• Are they anaemic? Are they clubbed?
• Height, Weight. Are they failing to thrive? Check health passport growth chart
• Lymphadenopathy - check cervical, axillary, epitrochlear & inguinal nodes
• A lymph node abscess which may be affecting or coming through the skin
• One or more soft swellings under the skin; these are not painful; the skin may have broken, leaving an ulcer with sharply cut edges and usually a clean base
• A discharging sinus (wound) near any joint
• Decreased unilateral chest expansion
• Dullness to percussion of the chest may suggest a TB pleural effusion, usually children > 5years
• Abnormalities on auscultation - crackles, coarse breath sounds
• Is there more air entering one side than the other, is there a wheeze on one side?
• Any signs of miliary TB e.g. hepatosplenomegaly?
• A swollen abdomen, especially if a lump is felt and if the lump remains after treatment for worms
• A spinal gibbus
• Swelling of a joint, a limp on walking; a stiff spine and child is unwilling to bend his back
• Neck stiffness or cranial nerve palsy

Investigations

• 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

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

• 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