HomePediatric TB disease, when compared with adult TB disease, is less likely to be microbiologically confirmed, due to its paucibacillary nature (less than 40% are culture positive); therefore, a negative microbiological test result should not be used to exclude TB disease.21 Mycobacterial confirmation of the diagnosis should be attempted by collecting multiple specimens. This is particularly important when (1) an isolate from a source case is not available or there are multiple possible sources; (2) the source case has drug-resistant TB; (3) the child is immunocompromised; or (4) the child has extra-pulmonary disease.22,23 In cases where pulmonary disease is minimal (ie, hilar adenopathy only), all other diagnoses have been excluded and only one drug-sensitive potential source case has been identified, then cultures are sometimes omitted and the source case sensitivities are used to guide management.
Gastric aspiration has been the collection procedure of choice in young children who are unable to produce sputum for the investigation of pulmonary TB. Some of the drawbacks of this technique are that it is more invasive, may be less tolerated by children and caregivers, may require hospitalization and has specific laboratory handling requirements.24,25 Details about gastric aspiration, including links to online resources with videos, are available in Appendix 1.26
Alternate ways to collect sputum have been developed, including sputum induction and nasopharyngeal aspiration. A systematic review on alternative sputum collection methods for pediatric pulmonary TB found significant heterogeneity between studies and differences depending on the pretest probability of TB disease.21 The study found that samples obtained from gastric aspiration or sputum induction had low positivity for both Gene Xpert and mycobacterial culture. The study showed a benefit in collecting at least two sputum specimens using either the same sample collection method or a different collection method. Regardless of the technique used, positive smear results do not differentiate between M. tuberculosis complex and non-tuberculous mycobacteria, which can cause false positive results.23
Sputum induction has been performed safely in infants as young as one month of age. Details about the procedure and a link to a video are available in Appendix 1. The advantages of sputum induction over gastric aspiration include a shorter period of fasting, no killing of the organisms by gastric acid and higher acceptability to staff and parents.27 Attention to safety issues, including pretreatment with a bronchodilator and infection prevention control procedures to prevent nosocomial transmission, should be in place (see Chapter 14: Prevention and Control of Tuberculosis Transmission in Healthcare Settings).
The diagnostic yield from bronchoscopy is no higher than that of gastric aspiration or sputum induction.28 Bronchoscopy may be useful in detecting tracheobronchial obstruction or for the exploration of alternative diagnoses.29
Other specimens can be collected if clinically indicated and include: bronchial washings, pleural fluid, cerebrospinal fluid (CSF), urine, other body fluids or tissue biopsy specimens. Fine-needle aspiration biopsy has been useful in children suspected of TB who present with palpable enlarged cervical nodes.30,31 However, surgical excision (removal) has the advantage of improving clinical outcomes, as lymph nodes may continue to enlarge and drain despite therapy to which the organism is susceptible.32 A lumbar puncture should be performed in cases of suspected congenital or neonatal TB and in infants with disseminated disease.33,34
Given the paucibacillary nature of childhood TB, the use of novel, noninvasive tests is being evaluated by some laboratories, both in Canada and internationally. As sputum is swallowed, particularly during sleep in young children, M. tuberculosis has been shown to be detectable in the stool.35,36 Systematic reviews evaluating stool Xpert (PCR) vs the microbiological reference standard have shown that the sensitivity ranges from 57-67% with a 98-99% specificity.37,38 Stool has specific processing requirements and commercial stool processing kits and methods have been developed.
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