Children struggle to provide sputum for TB tests, review shows

Tuberculosis diagnosis usually depends on testing sputum, the mucus coughed up from the lungs, but young children often cannot produce sputum on their own. To clarify how common this problem is and what alternatives are being used, a team led by Mary Gaeddert conducted a systematic review and meta-analysis focusing on children evaluated for presumed TB in health care settings in high burden countries. The researchers looked for studies published from January 2010 through June 2024 and registered their plan with PROSPERO (CRD42023473882). They set out to describe how often children could provide self-expectorated sputum, how often sputum induction with nasopharyngeal suctioning was used, and how often gastric aspirates and nasopharyngeal aspirates were collected. By assembling data from clinical studies in places with a heavy TB burden, the team aimed to show the practical challenges clinicians face when trying to obtain respiratory samples from children and to highlight where simpler sampling methods or new diagnostics might be most needed.

The review searched PubMed, Embase, the Cochrane Library, Web of Science, and clinical trials databases and identified 6,751 records, ultimately including 36 studies that enrolled 14,018 children across 14 high burden countries. Studies that did not report enough detail about respiratory sampling or were not done in high burden settings were excluded. The investigators extracted summary data, assessed risk of bias, and used random effects meta-analysis to combine results. They defined "sputum scarcity" as the proportion of children who could not provide a sample among those attempting. Key findings showed that in children under 5 years old, only about 4% (95% CI: 2-6%, n=5) provided self-expectorated sputum, and collection was not routinely attempted in many studies. In children aged 5 to 15 where one or two self-expectorated spot sputum samples were attempted, the pooled sputum scarcity was 38% (95% CI: 20-55%, n=6). Studies that used sputum induction with nasopharyngeal suctioning in children under 15 had a pooled scarcity of 3% (95% CI: 0-6%, n=8). For gastric aspirates, the median proportion without a sample was 0.0% (95% CI: 0.0-0.8%, IQR: 0.0-2.0%, n=23).

These results show that collecting respiratory samples from children with suspected TB is both complex and strongly tied to age. Very young children are rarely able to produce self-expectorated sputum and so depend on procedures such as sputum induction with nasopharyngeal suctioning or gastric aspirates to obtain material for testing. The low rates of missing samples for gastric aspirates suggest that alternative methods can be effective, but they may be more resource intensive or require special training and equipment. The review emphasizes the practical gap between standard sputum-based diagnostics and what is feasible for children, especially in resource-limited, high burden settings. The authors conclude that TB diagnostic approaches that use samples easier to collect from children are needed to improve detection and care. The work was supported by the Gates Foundation (INV-069540).