Aidsmap, 31 October 2011, by Lesley Odendal

A study in Indonesia has found that people with HIV who injected drugs were 85% more likely to have HIV-associated tuberculosis than those who were not injecting drug users. The findings were presented at the 42nd Union World Lung Health Conference held in Lille, France, last week.

The risk of TB in injecting drug users with HIV infection has rarely been quantified outside Western Europe and North America.

According to Dr van Crevel of the Radboud University in Nijmegen, Netherlands, who analysed a cohort of ARV-naive HIV-infected patients, made up of 658 injecting drug users (IDU) and 532 non-IDUs, injecting drug use was a significant risk factor for HIV-associated TB after controlling for CD4 count and other baseline characteristics such as age, gender and history of TB (hazard ratio 1.85, 95% confidence interval 1.28 - 2.67).

However, at baseline, 90 percent of the IDU arm was male compared to 37 percent in the non-IDU arm. 90 percent of the IDU arm was co-infected with hepititis C (HCV). Study participants were followed for a median of 260 days (IQR: 12-365 days) until the first episode of TB after HIV diagnosis.

Indonesia has the world's fifth highest TB case load and one of the most rapidly growing HIV epidemics, driven largely by injecting drug use. Drug use in Indonesia is most often found in higher socio-economic groups. Thus the increased risk of HIV-associated TB in IDUs is not associated with conditions of poverty, unlike in sub-Saharan Africa. 89 percent of the IDU participants had university degrees or higher education, compared to 72 percent in the non-IDU arm. Similarly, 72 percent of those who were injecting drug users had a job compared to only 47 percent in the non-IDU arm.

According to the researchers, the increased risk of TB in IDUs may be a consequence of more frequent exposure to TB when gathering in non-ventilated spaces to use drugs, leading to a higher rate of latent TB.

The researchers also propose that the increased risk may be due to biological reasons such as a higher HIV viral load or HCV coinfection. Animal studies have also shown an increased negative effect on the immune system when using opioids, which may contribute to the development of TB disease.

In Indonesia it is more popular to inject opioids than to smoke them, although IDUs often smoke tobacco (although this was not measured in this cohort), which is also associated with TB disease.

More research is required into the key cause of the increased risk of HIV-associated TB in IDUs but in the meantime health services should screen all HIV-infected IDUs for TB at every health visit and pay increasing attention to TB in injecting drug users, say the researchers.

The World Health Organization recommends that HIV and TB services for people who inject drugs should be integrated. Examples of integrated services were described in a May 2010 edition of HIV & AIDS Treatment in Practice, NAM's newsletter on HIV treatment in low and middle-income settings.

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