Battery-powered TB nucleic acid testing: 85% sensitive, 98% specific

Design

Cochrane systematic review and diagnostic accuracy meta-analysis

Population

3,291 people with presumptive pulmonary TB, 5 studies, 9 countries

Primary outcome

Sensitivity and specificity against culture

Effect

Sensitivity 85.4% (95% CI 82.2–88.1); specificity 97.6% (96.9–98.1)

This Cochrane review assessed near point-of-care nucleic acid amplification tests for pulmonary tuberculosis — battery-operated instruments designed for peripheral clinics without laboratory infrastructure. Only one marketed device met the WHO class definition, and five studies (3,291 participants in nine moderate-to-high-burden countries) tested it on sputum.

Against culture, summary sensitivity was 85.4% (95% CI 82.2 to 88.1) and specificity 97.6% (96.9 to 98.1), moderate-certainty evidence. In a group of 1,000 symptomatic people of whom 100 have tuberculosis, that means about 15 missed and 22 false positives. Sensitivity fell to 79% in people with HIV and 67% in smear-negative, culture-positive disease. Head to head, it was about 7.5 points less sensitive than Xpert MTB/RIF Ultra with similar specificity, and 22 points more sensitive than smear microscopy.

For laboratory physicians planning TB diagnostics, this positions the test between smear and the cartridge-based platforms: a real improvement where only microscopy is available, not a replacement for Xpert where it already exists. Most included studies ran the test in central laboratories, so field performance is not yet established, and there were almost no paediatric data. This is directly relevant to peripheral TB testing in India.

• Consider near point-of-care TB testing where smear microscopy is the only option; sensitivity was 22 points higher.
• Keep Xpert MTB/RIF Ultra where it is available; the near point-of-care test missed more cases.
• Do not use a negative result to exclude tuberculosis in people with HIV or high clinical suspicion.
• Send culture or a cartridge-based test when the near point-of-care result is negative but suspicion remains.
• Note that paediatric and true field-setting data are lacking.

Why it matters

It gives peripheral services a molecular option where smear microscopy has been the ceiling.

Don't overread it

Most testing was done in central laboratories, and only one device qualified; field accuracy is not yet established.

The statistics, in plain English

Sensitivity of 85% means about 15 in every 100 people with tuberculosis test negative. Specificity of 98% means about 2 in every 100 people without it test positive. Because most studies ran in laboratories, performance in a peripheral clinic may be lower; that is why certainty was downgraded.

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