Indian mother and child with TB.FLICKR, CALCUTTA RESCUE

The World Health Organization (WHO) will issue a recommendation against the use of widely available blood tests for the diagnosis of tuberculosis (TB) later this week. The warning—an unprecedented move for the organization—comes as a response to several studies that have found that the tests, which are commonly used in developing countries, produce too many false negatives and false positives to be considered reliable.

It is estimated that around one third of the world’s population is infected with Mycobacteria tuberculosis, but only around 5-10 percent of infected people develop the deadly respiratory disease. Currently, diagnostic methods in the United States and other developed countries consist of isolating and culturing the bacterium (known as the acid-fast smear test), as well as a nucleic acid amplification test for the bacterium’s DNA.

But in developing countries, there is a widespread and unregulated use...

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