Table 5.

Summary of investigations to diagnose tuberculosis in children

Investigation	Uses	Strengths and limitations
Microbiological studies
Microscopy	Diagnosis of TB	Strengths: Specificity high; useful in all specimen types; rapid (<1 h) detection; low cost. Limitations: Sensitivity very low, especially in young children; highly operator-dependent; labor intensive; unable to distinguish viable and dead bacilli.
Culture	Diagnosis of TB; drug susceptibility testing	Strengths: Specificity high. Limitations: Sensitivity moderate to low in young children; slow turnaround time; need proper laboratory facilities.
DNA detection (PCR)		Strengths: Specificity high; fully automated; rapid turnaround. Limitations: Sensitivity moderate to low in young children; unable to distinguish viable from dead bacilli.
Histopathological studies
Stained tissue samples	Diagnosis of TB	Allows exclusion of other diagnoses (such as malignancy).
Immune-based studies
TST; IGRA (e.g., Quantiferon Gold)	Diagnosis of Mtb infection	Neither test can differentiate Mtb infection from TB disease; careful evaluation of discordant results. TST: Affected by BCG vaccination; requires a second visit after 48–72 h. IGRAs: Unaffected by BCG vaccination; single visit; reduced sensitivity in very young and/or immune-compromised children; collecting adequate volume of blood and indeterminate results problematic.
Imaging
Radiography  CT and MRI  Ultrasonography	Diagnosis of TB	Chest radiography (AP and lateral views) most helpful; CT or MRI useful in uncertain or complicated cases; ultrasonography useful to identify intraabdominal/retroperitoneal lymphadenopathy or pleural/pericardial effusions, highly operator-dependent.

Data adapted from Perez-Velez and Marais 2012.

TST, tuberculin skin test; IGRA, interferon-γ release assay; CT, computed tomography; MRI, magnetic resonance imaging.