A battery-powered near point-of-care TB test was accurate but less sensitive than Xpert Ultra

Design

Cochrane systematic review of diagnostic test accuracy, WHO-supported

Population

5 studies, 3,291 people with presumptive pulmonary TB in nine countries

Primary outcome

Sensitivity and specificity for pulmonary TB against culture

Effect

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

This Cochrane review, supported by the World Health Organization, evaluated near point-of-care nucleic acid amplification tests (NPOC-NAATs), a new class of battery-operated molecular TB tests meant for peripheral health facilities and for use by staff with basic technical skills. It included five studies with 3,291 participants from nine countries with moderate to high TB burden. All five assessed a single marketed product, the MTB NAT Card with the MiniDock device, and only sputum was tested.

Against culture, summary sensitivity was 85.4% (95% CI 82.2 to 88.1) and specificity 97.6% (96.9 to 98.1), with moderate-certainty evidence. In a hypothetical 1,000 people of whom 100 have TB, the test would miss 15 and wrongly label 22 as having TB. Sensitivity was 79.2% in people living with HIV and 66.7% in smear-negative, culture-positive disease. Compared with Xpert MTB/RIF Ultra, sensitivity was lower (85.6% vs 93.1%; difference -7.5 percentage points) with similar specificity; compared with smear microscopy, sensitivity was higher (86.7% vs 64.7%) with slightly lower specificity.

Most studies ran the test in laboratories, not peripheral clinics, so the certainty was downgraded for applicability. Data in children were too limited to analyse. A negative result should not close the case in someone with a strong clinical suspicion, especially in HIV or smear-negative disease. The review makes no statement about regulatory status or availability in India.

• Treat the test as a rapid, more sensitive alternative to smear microscopy where a laboratory test is not available.
• A negative result does not exclude TB, particularly in people living with HIV or with smear-negative disease.
• Sensitivity was 85.4% overall, against 93.1% for Xpert MTB/RIF Ultra in head-to-head comparisons.
• Check which platform your programme uses and what its national guidance says before adopting this one.

Why it matters

Moving molecular TB testing closer to patients could cut the delay to treatment, if accuracy holds up outside laboratories.

Don't overread it

Only one product was evaluated, mostly in laboratories, so field performance and results in children are not established.

The statistics, in plain English

A sensitivity of 85.4% means about 15 in 100 people with TB test negative. The review's example shows the practical effect: in 1,000 symptomatic people with 100 true cases, 15 would be missed and 22 non-cases flagged.

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