Major changes in characteristics of TB epidemic in HIV-positive patients in New York

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The demographics and clinical characteristics of the tuberculosis epidemic amongst patients with HIV in New York City have changed significantly since the advent of antiretroviral therapy.

‘We found significant changes in the sociodemographic and clinical characteristics for both HIV-infected and HIV-uninfected tuberculosis patients in NYC, including increases in the proportions with culture-negative tuberculosis and with extrapulmonary tuberculosis and decreases in the proportion with multidrug-resistant tuberculosis and that died,” write investigators in the June 1st edition of Clinical Infectious Diseases.

The study also showed that the proportion of tuberculosis (TB) patients infected with HIV fell from 60% before 1992 to 22% in the period 2002 to 2005.

Glossary

adjusted odds ratio (AOR)

Comparing one group with another, expresses differences in the odds of something happening. An odds ratio above 1 means something is more likely to happen in the group of interest; an odds ratio below 1 means it is less likely to happen. Similar to ‘relative risk’. 

culture

In a bacteria culture test, a sample of urine, blood, sputum or another substance is taken from the patient. The cells are put in a specific environment in a laboratory to encourage cell growth and to allow the specific type of bacteria to be identified. Culture can be used to identify the TB bacteria, but is a more complex, slow and expensive method than others.

multidrug-resistant tuberculosis (MDR-TB)

A specific form of drug-resistant TB, due to bacilli resistant to at least isoniazid and rifampicin, the two most powerful anti-TB drugs. MDR-TB usually occurs when treatment is interrupted, thus allowing organisms in which mutations for drug resistance have occurred to proliferate.

pulmonary

Affecting the lungs.

 

AIDS defining condition

Any HIV-related illness included in the list of diagnostic criteria for AIDS, which in the presence of HIV infection result in an AIDS diagnosis. They include opportunistic infections and cancers that are life-threatening in a person with HIV.

Worldwide, TB is the single biggest cause of serious illness and death in people with HIV. Although the impact of the infection is greatest in resource-limited settings, TB is one of the most common AIDS-defining illnesses in the UK and many other industrialised countries.

Historically, HIV infection, especially when advanced, has been associated with unusual manifestations of TB. But it is unclear if this is still the case since the introduction of effective antiretroviral therapy. Therefore, investigators analysed the characteristics of the disease in New York City between 1992 and 2005.

This period was divided into three eras: 1992-95 (pre-HIV treatment); 1996-2000 (early HIV treatment); 2001-2005 (late HIV treatment).

A total of 7224 TB cases were diagnosed in New York between 1992 and 1995, and 60% of these involved patients with HIV.

The total number of diagnosed TB infection fell between 1996 and 2000 to 5933, and only a third of patients were co-infected with HIV.

Further progress was made against the disease after 2001, the total number of cases falling to 3815, with 22% of diagnoses involving patients with HIV.

Over the course of the study there were significant changes in the sociodemographic profile of HIV-positive TB patients. The patients become older, and an increasing number of infections involved women. TB diagnoses in individuals infected with HIV heterosexually increased, but the proportion of cases involving injecting drug users fell.

There was also a significant increase in the number of cases involving foreign-born patients (13 to 38%, p < 0.001).

The proportion of patients with extrapulmonary disease only increased from 12% in the pre-treatment era to 18% in the period after 2001 (p < 0.001). In addition, there was an increase in the percentage of patients who had both pulmonary and extrapulmonary disease (from 20 to 28%, p < 0.001)

Closer analysis of this finding showed that the increase in extrapulomary disease only was significant only amongst US-born patients (from 11 to 17%, p < p.001).For disease involving both the lungs and other sites, the increase was only significant for those born outside the US (from 22 to 31%, p < 0.001).

Before 1995, 7% of TB cases in patients with HIV were culture-negative. This increased to 21% by 2005. There was a modest fall in the proportion of smear-positive case after the introduction of HIV treatment (from 43% before 1995 to 40% in the period 1996 to 2000, p = 0.15).

A significant drop in the proportion of HIV-infected patients with multidrug-resistant TB was observed (from 16 to 4%, p < 0.001).

Mortality rates also fell. However, even in the period 2002 to 2005, HIV-infected patients with TB still had a higher mortality rate than HIV-negative patients (18% vs 3%).

Statistical analysis confirmed the increased risk of extrapumonary disease after HIV treatment was introduced (adjusted odds ratio [AOR] = 1.35; 95% CI, 1.12 to 1.63). It also increased that there was a significant increase in the risk of TB affecting both the lungs and other sites (AOR = 1.79; 95% CI, 1.55 to 2.06).

The investigators’ analysis also showed that the introduction of HIV therapy was accompanied by an increased likelihood of TB being culture negative (AOR = 1.68; 95% CI, 1.38 to 2.04).

Compared to the period before 1995, HIV-positive patients in the early HIV treatment era had a 49% reduction in their risk of dying before TB therapy was initiated, and a 59% reduction in their mortality risk during TB treatment.

“The clinical presentation of tuberculosis has changed substantially in 14 years … awareness of these changes may help clinicians diagnose tuberculosis more promptly, especially in HIV-infected patients,” write the investigators.

They conclude, “prompt diagnosis of tuberculosis and initiation of treatment is especially important in HIV-infected patients, because they continue to experience higher mortality. Future studies should prospectively evaluate the risk of developing tuberculosis and its presentation among HIV-infected patients with well-managed HIV infection and those with poorly controlled disease.”

References

Harris TG et al. Changing sociodemographic and clinical characteristics of tuberculosis among HIV-infected patients, New York City, 1992-2005. Clin Infect Dis 50: 1524-32, 2010.