Chris Patalano — July 23, 2009 – 5:57 pm
Scientists, researchers, clinicians, and technical experts weren't the only ones busy at this week's fifth annual International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention. I took some time away from the conference venue to walk in a TB-HIV march organized by South Africa's Treatment Action Campaign (TAC). The march of several thousand began near the Cape Town city hall and ended in a rally at the conference venue, and took place as a way to collectively demand better TB diagnostics and access to treatment for drug-resistant tuberculosis.
TAC is an indispensable NGO working on HIV and TB issues, and is renowned not only in this country, but globally, for securing the government's commitment to provide free antiretroviral (ARV) treatment to people living with HIV. TAC is now working through a variety of channels - including the legal system - to ensure access to ARVs and other vital services for everyone who needs them. With a presence in Khayelitsha and other townships throughout South Africa, where rates of TB-HIV co-infection are among the highest in the world, TAC knows what the greatest needs are. Not only do TB and HIV/AIDS services need to be integrated, but there's an urgent need for more resources to research and develop TB diagnostics that quickly and effectively diagnose TB in people with HIV.
It's a devilish paradox. Tuberculosis is the most common illness and leading cause of death among people with HIV. Yet the standard TB diagnostic test - an antiquated and insensitive test in its own right - does an even worse job of detecting TB in people with HIV. This test, called sputum smear microscopy, involves a patient, a health worker, a technician, and a microscope. The patient must first cough up phlegm - or "sputum" -which the health worker collects (infants and children have a hard time producing sputum). The sputum gets smeared on a glass slide, which a technician then examines under a basic light microscope, searching for the TB bacilli. This absurd Where's Waldo? approach to diagnosis, not surprisingly, in most cases fails to turn up the TB germ -even in people who haven't been infected with HIV.
It happens, though, that people with HIV who have tuberculosis are less likely to show TB bacilli in their sputum. They're also more likely to have TB that affects areas of the body outside the lungs - the lymph nodes, the spine, the blood, or the brain. TB can infect literally any part of the body, most of which don't produce sputum, requiring a clinical diagnosis.
It gets worse. The "gold standard" of TB diagnostics is the "culture test." This test involves taking the sputum, placing it in a petri dish, and cultivating colonies of the TB germ. If the germs grow, that's proof that the patient has tuberculosis - even if the microscopy exercise failed to find Waldo. As it happens, though, TB is a slow-growing bug, requiring weeks for colonies to grow large enough to see. As basic as this basic test is, it's not available in many resource-poor settings.
This doesn't even touch on the test to determine whether the particular strain - or strains - of TB that infect a person are susceptible to the drugs available to treat them. Multidrug-resistant TB (MDR-TB) now affects over half a million people every year. New extensively drug-resistant (XDR) strains, identified in just the past two years, thwart most of the available drugs and have turned up in every country with the capacity to test for them. The test to determine drug-resistance takes months to administer, meaning most people with HIV who also have drug-resistant TB die before their results are even finished. South Africa is home to one of the only labs in sub-Saharan Africa that can perform this test. As a result, the extent to which XDR-TB has spread on the continent remains anybody's guess.
At the conference, the Foundation for Innovative New Diagnostics (FIND) announced the development of a new tabletop machine that can detect resistance to Rifampicin-the most important anti-TB drug - within 30 minutes, using a sputum sample. This is definitely a welcome start. But what we ultimately need for TB is the same that's available for HIV: a simple "dip stick" test administered at the point of care and that yields results in minutes or hours, not weeks or months - time that might as well be eternity for many of those with co-infection. In my previous post, I described how concerted activism for HIV/AIDS led to the development of such advanced tools within decades of the discovery of HIV.
Those participating in the TAC march - most of whom were from affected communities - sent a clear and salient message to the political leadership of South Africa and the wealthy G8 countries: the global economy might be in recession, but TB and HIV/AIDS are not. Provide the resources to propel the fight against TB-HIV from the 19th century to the 21st, including diagnostics and treatments for MDR- and XDR-TB that work for people with HIV/AIDS.