HAART just as effective in HIV/TB coinfected patients

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HIV-positive patients with active tuberculosis (TB), who receive anti-TB therapy and HAART are just as likely as HAART-treated HIV-positive patients without TB to benefit from antiretroviral therapy, according to a Taiwanese study published in the December edition of AIDS. The investigators also found that the TB patients were at no greater risk of developing AIDS developing illnesses or dying than the non-TB patients were.

TB accounts for a third of all HIV deaths worldwide and several studies have suggested that TB hastens HIV disease progression. However, most of these studies were conducted either before HAART became available, or in patient populations who did not have access to HAART, principally in southern Africa.

To see if HIV-positive patients with TB had a worse virological and immunological response to HAART, and accelerated disease progression, investigators in Taiwan conducted an eight year prospective study between 1994 and 2002, involving a total of 716 HIV-positive patients, 125 of whom also had active TB.

Glossary

p-value

The result of a statistical test which tells us whether the results of a study are likely to be due to chance and would not be confirmed if the study was repeated. All p-values are between 0 and 1; the most reliable studies have p-values very close to 0. A p-value of 0.001 means that there is a 1 in 1000 probability that the results are due to chance and do not reflect a real difference. A p-value of 0.05 means there is a 1 in 20 probability that the results are due to chance. When a p-value is 0.05 or below, the result is considered to be ‘statistically significant’. Confidence intervals give similar information to p-values but are easier to interpret. 

disease progression

The worsening of a disease.

prospective study

A type of longitudinal study in which people join the study and information is then collected on them for several weeks, months or years. 

naive

In HIV, an individual who is ‘treatment naive’ has never taken anti-HIV treatment before.

log

Short for logarithm, a scale of measurement often used when describing viral load. A one log change is a ten-fold change, such as from 100 to 10. A two-log change is a one hundred-fold change, such as from 1,000 to 10.

Before HAART became available in 1997, antiretroviral therapy consisted of two nucleoside analogues, and patients with TB were also given anti-TB therapy consisting of four drugs including rifampicin.

Patients with TB were older (median age 37 years versus 34 years, p=0.03), and were more likely to have had heterosexual sex as their risk factor for HIV infection (p=0.005).

Of the 276 antiretroviral naïve patients who initiated anti-HIV therapy during the course of the study, 46 were also coinfected with TB. Individuals with TB were significantly more likely to have a lower CD4 cell count at baseline (median 37 cells/mm3 versus 79 cells/mm3, p=0.0004) and to have a higher median viral load (5.64 log versus 5.40 log, p=0.003).

Despite this, comparable numbers of TB and non-TB patients achieved a viral load below 400 copies/mL after four weeks of anti-HIV therapy (43.5% versus 46.5%, p=0.71). The median increase in CD4 cell count at week four was also comparable for the TB and non-TB patients (71 cells/mm3 versus 64 cells/mm3, p=0.70).

Investigators also found that similar proportions of TB and non-TB individuals experienced virological failure after taking HAART for four months or longer (38.2% versus 25.7%, p=0.14).

However, the investigators initially found that patients with TB were at greater risk of developing an additional AIDS-defining illness (risk ratio 1.16) or dying (mortality rate 14.31 per 100 patient years of follow-up versus 9.98 for non-TB patients). However, when they excluded TB patients who died within 30 days of starting anti-TB therapy, they found that TB patients had a comparable median survival time to non-TB patients (379 days versus 243 days, p=0.24).

"In this study" the investigators comment, "we found that TB did not alter the virological and immunological responses in antiretroviral naïve patients when antituberculosis therapy and HAART was continued … we further demonstrated that the risk for HIV progression was similar between TB and non-TB patients, regardless of higher or lower baseline CD4 cell counts at TB diagnosis."

They suggest that their findings differ from those of earlier studies that found that HIV-positive patients with TB experienced faster disease progression, due to the availability of HAART and rifampicin-based TB therapy for their patients. They note that many of the studies that found poorer survival were conducted in Africa where neither is available.

Further information on this website

Tuberculosis - factsheet

Tuberculosis - overview

Combining ARVs with treatment for TB - HATIP 3

References

Hung C-C et al. Improved outcomes of HIV-1-infected adults with tuberculosis in the era of highly active antiretroviral therapy. AIDS 17: 2615 – 2622, 2003.