TB in an HIV setting: double trouble
More effective and affordable diagnostic tests able to detect TB in HIV positive patients, including extra-pulmonary cases and among children. These tests need to be easy to use even where there is little infrastructure or training.
Celestine is a 28-year old Kenyan widow and mother of three living with HIV/AIDS. Hakan Yaman, her doctor, wants to start her on antiretrovirals. Celestine is losing weight and can scarcely walk, and Hakan suspects she might have tuberculosis too. Should she be put on TB treatment? Or should she just be started on antiretroviral treatment?
The problem for Celestine, and the dilemma for Hakan, is that the traditional means of diagnosing TB - sputum smear analysis and chest X-rays - are not conclusive in people with HIV.
"It's so difficult. We need to know if a person with HIV/AIDS has TB but we can't diagnose it. Their sputum smear tests are often negative and we can't tell if they're losing weight from TB or HIV," says Hakan.
The TB diagnostic test currently in use, the smear sputum test, only detects about half of all cases with tuberculosis. This falls to one third in HIV positive patients. The test is of no use in diagnosing extra-pulmonary tuberculosis, which accounts for at least 20% of TB diagnoses in HIV infected people.
"A chest X-ray might not tell you a lot either, as HIV positive patients often don't have typical TB-related changes in their lungs," Hakan points out.
The other problem is the drugs that Celestine would have to take. "The existing TB drugs are older than I am," says Dr Yaman. The four main drugs used in Kenya are isoniazid, rifampicin, ethambutol and pyrazinamide. Isoniazid has been on the market since 1952, pyrazinamide is the most recent, in use since 1970. If Celestine is prescribed these drugs, Kenyan TB protocols specify that she will need to stay on treatment for at least eight months, under direct observation by medical personnel.
"Patients just can't afford it: every time they're with us is a day they're not working," says Hakan. Celestine has three children to send to school, and if she cannot afford to return to the clinic to finish her treatment, she risks developing a drug-resistant form of TB, which is much more difficult to treat. If she has untreated TB on top of HIV/AIDS, this will be fatal.
As it turned out, Celestine and Hakan Yaman were lucky. Put on TB treatment, Celestine flourished, gaining eight kilograms in as many weeks. Hakan was able to delay ARVs until the end of the intensive treatment phase so Celestine's TB and HIV medicines didn't interact. Lucky dips can have good outcomes - but doctors would agree that they are not a good way to practice medicine.
What is needed:
- More effective and affordable diagnostic tests able to detect TB in HIV positive patients, including extra-pulmonary cases and among children. These tests need to be easy to use even where there is little infrastructure or training.