Molecular tests for tuberculosis are most sensitive when there are many bacilli in the sample. In smear-negative disease, in people with HIV and in children, sensitivity falls, so a single negative result can miss a real infection.
When clinical suspicion remains high, the options are a second good-quality sputum sample, sputum culture, induced sputum or other specimens, and chest imaging. A clinical decision to treat, made carefully and recorded, is still sometimes the right call.
- Send a second good-quality sputum sample when suspicion remains high after a negative molecular test.
- Request culture where available in smear-negative cases and in people with HIV.
- Use chest imaging and clinical course to support or refute the diagnosis.
- Record the reasoning when deciding to treat without microbiological confirmation.
Why it matters
The patients a molecular test is most likely to miss are often the ones most harmed by a delay.
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