Steep fall in incidence of TB among HIV-positive heterosexuals in the UK

Incidence of tuberculosis (TB) among HIV-positive heterosexual people in England and Wales declined significantly between 2002 and 2010, investigators report in the online edition of AIDS. The fall is attributed to changes in the epidemiology of HIV in the UK and increased uptake of antiretroviral therapy. The vast majority of TB diagnoses – 84% – involved people from sub-Saharan Africa.

However, the authors caution that their results leave no room for complacency and point to the need to adhere to HIV and TB testing guidelines. “Our findings reinforce the need for stricter implementation of existing testing guidelines in the HIV and tuberculosis clinic setting, and support the recommendation for primary care practitioners to consider the risk of both diseases in migrant patients from high prevalence countries.”

Most cases of heterosexual HIV in the UK involve people born in sub-Saharan Africa. There is a high prevalence of TB in this region. As a result, a substantial number of HIV-positive, heterosexual people in the UK are likely to have been exposed to TB.

It is recommended that all HIV-positive people in the UK should be screened for TB. Despite this recommendation, the incidence of active TB in this population is unknown.

A team of investigators examined three national databases to establish the incidence of TB among HIV-positive heterosexuals living in England and Wales between 2002 and 2010. Their analysis also allowed the investigators to establish the risk factors associated with a TB diagnosis.

A total of 45,322 heterosexual people received HIV care in England and Wales during the period of the study. Active TB was diagnosed in 4266 individuals (9.4%).

Over half (54%) received a simultaneous diagnosis of HIV and TB; 8% were diagnosed with TB more than three months before their HIV diagnosis; and 38% were diagnosed with TB more than three months after their HIV infection was detected.

“Active tuberculosis may have been prevented in some cases had testing and treatment for latent tuberculosis been a routine part of the initial assessment at the time of HIV diagnosis,” suggest the authors.

Almost all (92%) of the people who received a simultaneous diagnosis had their HIV diagnosed late, and 53% had a CD4 cell count below 100 cells/mm³.

Some 84% of TB diagnoses involved black African people. Factors associated with TB co-infection included sex (male vs female, AOR = 1.29, 95% CI, 1.15-1.44); ethnicity (black African, AOR = 3.41, 95% CI, 2.45-4.76; Indian, Pakistani or Bangladeshi, AOR = 4.37, 95% CI, 2.63-7.26), and acquiring HIV infection abroad (AOR = 2.31, 95% CI, 1.77-3.01).

Between 2002 and 2010, incidence of TB among HIV-positive heterosexuals fell from 30 per 100 to 8.8 per 1000. This fall was highly significant (p < 0.01).

“This decline is due to a modest fall in the absolute number of incident tuberculosis diagnosis…and a large increase in the total number of heterosexual adults living with diagnosed HIV,” explain the authors.

They believe patients are becoming less susceptible to TB. “Firstly, the fall in TB diagnoses has coincided with a decline in the overall number of heterosexuals in the UK acquiring their HIV infection in sub-Saharan Africa, where there is a high prevalence of tuberculosis. Secondly, in recent years, the uptake of ART [antiretroviral therapy] among persons with a CD4-cell count < 350 cells/mm³ has increased in line with national HIV treatment guidelines.”

Nevertheless, TB incidence among HIV-positive heterosexual people was still significantly higher than that seen in the general UK population (0.14 per 1000). The incidence of TB reported among HIV-positive black Africans (11 per 1000) was approximately four times higher than the UK rate for HIV-negative Africans born abroad (2.7 per 1000) and 25 times higher than the rate among HIV-negative black Africans born in the UK (0.43 per 1000).

The incidence of TB among people not taking antiretroviral treatment was over 14 times higher than that seen in people taking anti-HIV drugs (56 per 1000 vs 3.9 per 1000; p  < 0.01). The highest TB incidence throughout the period of the study was among people not taking HIV therapy who had a CD4 cell count below 200 cells/mm³.

“We have reported a significant decline between 2002 and 2010 in the annual tuberculosis incidence rate among heterosexual adults living with diagnosed HIV in England and Wales. However, the tuberculosis incidence rate in 2010…greatly exceeds that in the general population,” conclude the investigators.