Table 6.
Bacteriologic specimen collection methods—perceived problems and/or benefits
| Specimen collection method | Problems/Benefits | Potential clinical application |
|---|---|---|
| Sputum | Not feasible in very young children; assistance and supervision may improve the quality of the specimen | Routine sample to be collected in children >7 yr of age (all children who can produce a good quality specimen) |
| Induced sputum | Comparable yield to gastric aspirate; no age restriction; specialized technique, which requires nebulization and suction facilities; potential transmission risk | To be considered in the hospital setting on an in- or out-patient basis |
| Gastric aspirate | Unpleasant procedure, but not difficult to perform; requires fasting; sample collection advised on 3 consecutive days | Routine sample to be collected in hospitalized who cannot produce a good quality sputum specimen |
| Nasopharyngeal aspiration | Less invasive than gastric aspirate; no fasting required; comparable yield to gastric aspirate | To be considered in primary health care clinics or on an outpatient basis |
| String test | Less invasive than gastric aspirate; tolerated well in children >4 yr; bacteriologic yield and feasibility requires further investigation | Potential to become the routine sample collected in children who can swallow the capsule but cannot produce a good quality sputum specimen |
| Bronchoalveolar lavage | Extremely invasive | Only for use in patients who are intubated or who require diagnostic bronchoscopy |
| Stool | Culture not practical, DNA extraction difficult; not invasive; M. tuberculosis excretion well documented | Reasonable yield using Gene Xpert |
| Urine | Not invasive; excretion of M. tuberculosis components | Lipoarabinomannan (LAM) assay has poor sensitivity; unreliable in children |
| Blood/Bone marrow | Good sample sources to consider in the case of probable disseminated TB | To be considered for the confirmation of probable disseminated TB in hospitalized patients |
| Cerebrospinal fluid (CSF) | Fairly invasive; bacteriologic yield low | To be considered if signs of tuberculous meningitis |
| Fine needle aspiration (FNA) | Minimally invasive using a fine 23G needle; excellent bacteriologic yield; minimal side effects | Procedure of choice in children with superficial lymphadenopathy |
Data adapted from Marais and Pai 2006.