TUBERCULOSIS / TB (MYCOBACTERIUM TUBERCULOSIS)
Dr. Ira Shah
Incharge Pediatric HIV and TB Clinic, B.J.Wadia Hospital for Children, Mumbai, India Consultant in Pediatric Infectious Diseases, Nanavati Hospital, Mumbai, India
When to suspect TB
Suspect TB if the child has:
- Contact with adult who has Pulmonary TB
- Fever for more than 1 week
- Chronic cough (more than 3 weeks)
- Ongoing weight loss or poor weight gain.
- Mantoux test
- Gastric lavage isolation / sputum for culture and smear
- Radio logical - Chest X-ray.
Mantoux test / MT (Tuberculin test) :
- Culture of affected body fluid or tissue obtained by fine needle aspiration or biopsy.
Can be done from 3 months onwards using 5 TU PPD injected intradermally. Induration more than 5 mm is considered positive in HIV
infected children. However, negative test may be seen in over 50% of children with tuberculosis
. Thus, a negative test does not exclude TB.
Gastric lavage / sputum examination :
Though acid fast stained sputum smears are positive in 50-70% of adults with Pulmonary TB, children with TB disease rarely produce sputum voluntarily and have a low bacterial load (17). Three consecutive morning gastric aspirates have a yield of about 30-70% and have a better yield on culture.
Other fluids and tissues for culture :
Bronchoalveolar lavage (BAL), lung biopsy, lymph node biopsy, serosal fluids and CSF. Specimens should be cultured for 2-6 weeks either by radiometric culture methods (Bactec) or culture on L-J medium. Antimycobacterial drug sensitivity should be done on the initial positive culture if treatment fails or relapse occurs. If no organism is isolated from the specimen of the child, drug sensitivity test can be done on the isolate from the source case.
- Localized pulmonary infiltrates with hilar adenopathy
- Middle lobe collapse and consolidation
- Pleural effusion
- In older children and adults - cavitatory tuberculosis
PCR assays are not useful as primary diagnostic tool because a negative PCR does not rule out TB and a positive result does not absolutely confirm M. Tuberculosis infection. Also false positive rates are high with sensitivity ranging from 45-83% (18-20). Serological tests for TB are not very specific.