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\n A woman diagnosed with tuberculosis receives care at Barawe General Hospital in Somalia.<\/p>\n
Andrew Renneisen\/Getty Images<\/p>\n
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Andrew Renneisen\/Getty Images<\/p>\n
Tuberculosis has earned the undesirable distinction of being the world’s top infectious disease killer \u2014 a mantle it took back from COVID in 2023. TB claimed the lives of 1.23 million people<\/a> in 2024 and sickens about 10 million people<\/a> each year.<\/p>\n Research is now casting doubt on the true number of TB cases.<\/p>\n A new study published in Nature Medicine<\/a> found that many TB diagnoses may be incorrect \u2014 and that this could carry significant implications for patient care and well-being.<\/p>\n The study analyzed data from 111 low- and middle-income countries in 2023. Since nobody knows the true number of TB patients, Nicolas Menzies<\/a> \u2014 a co-author on the paper and an associate professor of global health at the Harvard T.H. Chan School of Public Health \u2014 says he and his colleagues used data on the number of TB cases submitted to the World Health Organization and came up with a formula to estimate false negatives and false positives. However you slice the numbers, he says, the headline conclusion is the same: There are an awful lot of incorrect diagnoses.<\/p>\n Menzies and his colleagues estimate that, of those who seek medical care for symptoms that could indicate a TB infection, about a million people have the disease but aren’t given that diagnosis. They are false negatives. On the flip side, the estimated number of false positives was even worse: 2 million or more people each year are erroneously told they have TB when they actually have something else.<\/p>\n “Amongst all of those individuals who are diagnosed and treated for TB every year, perhaps a quarter of them \u2014 and maybe even higher \u2014 might not have TB disease,” Menzies says. He says that in the most serious cases, these patients could have a potentially fatal disease like pneumonia, lung cancer or chronic obstructive pulmonary disease. He says this type of misdiagnosis has been a “blind spot” in the TB world.<\/p>\n The study has been both praised \u2014 and criticized \u2014 by outside experts.<\/p>\n Its attention to incorrect TB diagnoses is an important step, says Dr. Marcel Behr<\/a>, a professor of medicine at McGill University who was the founding director of the McGill International TB Centre<\/a>. “The issue about whether we have false positives has been understudied,” he says, adding that he was impressed with the research’s “rigorous approach.”<\/p>\n But to Dr. Lucica Ditiu<\/a>, a pulmonologist who is head of Stop TB Partnership, that emphasis on false positives could backfire. She worries that the study could cast doubt on TB statistics, prompting governments and global health funders to shift their dollars elsewhere. Ditiu also fears that the misdiagnosis angle could make clinicians reluctant to diagnose the disease lest they make a mistake.<\/p>\n The reason for the misdiagnoses\u00a0 <\/p>\n Why are there so many false positives and missed cases?<\/p>\n Menzies’ theory: less-than-perfect diagnostic tests \u2014 and human error.<\/p>\n There are a variety of ways to diagnose TB but most tests rely on sputum \u2014 mucus coughed up by a patient \u2014 that is then analyzed for signs of the tuberculosis bacterium. The accuracy rate varies hugely, with the newer PCR machine analysis far more accurate than traditional methods of examining a sample under a microscope.<\/p>\n