Conventional TB tests fail millions, say health experts

Eight-year-old Simon Njeri was in and out of hospital much of last year until his mother, Teresa, went to a drop-in centre in Kayole, Nairobi, run by Women Fighting AIDS in Kenya.

A doctor there quickly diagnosed extra-pulmonary tuberculosis and put Simon first on TB drugs, then on antiretrovirals, for both mother and son are HIV-positive. Six months later Simon was back at school.

Tuberculosis kills two million people worldwide every year, but the standard tools for its detection and treatment fail to reach the majority of sufferers, who are HIV-positive patients, according to the Campaign for Access to Essential Medicines run by humanitarian agency Me'decins Sans Frontie`res (MSF).

The most widely used diagnostic test, the so-called smear sputum, picks up active pulmonary TB but fails to detect extra-pulmonary and latent TB, most frequent among HIV-positive sufferers and children.

As AIDS progresses, patients test TB-negative even though they harbor the bacterium. AIDS also complicates TB clinical diagnosis because opportunistic infections produce similar symptoms.

"Half of our patients have negative smears but keep getting sicker because of TB," said Gilles van Cutsem, head of an MSF-run TB/AIDS clinic in Khayelitsha township in South Africa - one of the world's worst countries for the twin TB/AIDS epidemic.

A rate of 250 TB patients per 100,000 inhabitants is considered high-burden. Khayelitsha has 1,500.

LEADING CAUSE OF DEATH

South Africa has the world's largest number of HIV-positive people - about five million. Two out of 10 people aged 15-49 are infected, according to the United Nations' HIV/AIDS body, UNAIDS.

Worldwide, 12 million people are co-infected with HIV/AIDS and TB, and two-thirds live in Sub-Saharan Africa.

Although curable, TB is the leading cause of death among HIV-positive people. It appears earlier than other opportunistic infections, advances faster and is fatal if left untreated because undetected.

More sophisticated tests than the 122-year-old smear sputum are used in the West but they are too complex and expensive for poor, TB-endemic countries.

MSF's Campaign for Access to Essential Medicines urges international partnerships, such as the Bill Gates-funded Foundation for Innovative New Diagnostics, to quickly adapt these tests to poor countries and make them affordable and accessible.

Treatment is a second problem. The worldwide anti-TB strategy, launched in 1994 by the World Health Organisation, is called Directly Observed Treatment Short-course, or DOTS. The campaign argues that DOTS improved over previous disorganized attempts at TB control but fails in the context of AIDS and poverty.

Its cornerstones are the sputum smear test, which is inadequate for AIDS, and treatment, in the form of a daily pill taken for six to eight months.