MICHEL MARTIN, HOST:
Tuberculosis is the world's deadliest infectious disease. One-point-two million people died of TB in 2024, that according to official numbers, plus 10 million get sick from it each year. But as NPR's Gabrielle Emanuel reports, a new study in Nature Medicine is casting doubt on those numbers.
GABRIELLE EMANUEL, BYLINE: Nicolas Menzies has spent years poring over TB data, and he's zeroed in on an issue.
NICOLAS MENZIES: Problem is that the tests we have for TB disease are, frankly, not very good.
EMANUEL: Menzies coauthored the new study and is a professor at Harvard School of Public Health. He says well over a third of TB diagnoses in low- and middle-income countries don't actually use TB tests. They're made by a doctor or nurse looking at a patient's symptoms.
MENZIES: Prolonged cough, weight loss, night sweats, things like this.
EMANUEL: Between imperfect tests and human error, Menzies says there are a lot of misdiagnoses. He says, often, the TB diagnosis is missed. And even more often, people are incorrectly told they have TB.
MENZIES: Amongst all of those individuals who are diagnosed and treated for TB every year, perhaps a quarter of them, and maybe even higher, might not have TB disease.
EMANUEL: That may mean they have another condition, perhaps as serious as lung cancer or pneumonia. This has real consequences - the cost of the grueling, monthslong TB treatment, plus the side effects. And worst of all, Menzies found in another study done in Brazil that patients who are incorrectly diagnosed...
MENZIES: Actually have much worse outcomes, much higher mortality rates than those people who were being treated for TB.
EMANUEL: They're chances of dying were almost double, likely because whatever condition they actually had needed prompt treatment. Marcel Behr founded the McGill International TB Centre. He praises the rigor of the study.
MARCEL BEHR: The issue about whether we have false positives, I think, has been understudied.
EMANUEL: He sees this paper as a call to improve TB tests and also to get health workers to use the tests that do exist and are better than they once were.
BEHR: It takes a little while for doctors to adapt. They say, I'm used to treating this as TB - we have a lot of TB here, so I'm going to continue to treat it as TB.
EMANUEL: But the study also has its critics. Lucica Ditiu heads the Stop TB Partnership.
LUCICA DITIU: If the purpose of the paper is to say that we need better tools, better diagnostics, that I think is spot on. If it is to say that, oh, my goodness, clinical diagnosis is so bad, then this is very damaging.
EMANUEL: She says clinical diagnosis is key, especially in remote areas. She says her focus is on access to tests and to doctors.
DITIU: Our biggest problem in TB is we have a huge number of people that are not diagnosed at all in any shape or form, millions.
EMANUEL: Shifting the focus away from these patients to all the incorrect diagnoses could backfire, she says. She worries doctors will be reluctant to diagnose in case they might make a mistake, and global health funders could grow hesitant to fund treatment. Menzies doesn't want to see that happen. But he says it's critical to get a clear picture of true TB rates.
Gabrielle Emanuel, NPR News. Transcript provided by NPR, Copyright NPR.
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