Study suggests TB screening needs to be targeted for maximum public health benefit

May 19, 2009,

New estimates of the likelihood that a latent case of tuberculosis (TB) will become active have resulted in a roughly 50 percent increase over previous estimates of the number of people needed to be screened (NNS) to prevent an active infection, limiting the cost effectiveness of screening in many Center for Disease Control and Prevention (CDC)-defined risk groups, according to an analysis conducted by experts in the epidemiology of the disease.

The research will be presented at the American Thoracic Society's 105th International Conference on Tuesday, May 19.

"Screening for LTBI [latent infection] is an important method for eliminating the diseases," says lead researcher Benjamin Linas, M.D., M.P.H., of Massachusetts General Hospital. "This analysis, does not suggest we reduce screening. Indeed, if we did that, we'd likely take a step backward in TB control. The study does suggest, though, that we redirect and focus our screening efforts on those most at risk."

Among patients with chronic medical conditions, the NNS to prevent an active case of TB ranged from 1,150 for those who are underweight to 2,778 for patients with end-stage renal disease. Previous estimates of the NNS ranged from 806 to 1,923. Screening was not cost-effective for many patients who are currently recommended for screening, including those who are underweight, have had a gastrectomy, or have silicosis, diabetes or end stage renal disease. Screening was a cost-effective strategy under previous estimates of the rate of reactivation TB, but the new, lower estimates of reactivation limited the case finding rate and decreased the cost effectiveness of screening.

The NNS was lower in populations with a high prevalence of latent TB infection, including foreign-born residents, recent immigrants, the homeless and injection drug users. It was also lower in patients with a high risk of reactivation TB, including those with and those taking immunosuppressive medications. As a result, screening remained cost effective for these groups.

Dr. Linas and his colleagues, from MGH and Boston University School of Public Health, based their analysis on several new estimates of TB reactivation rates gathered from 1998-2005. According to Dr. Linas, current guidelines for screening are based on rates indicated from studies conducted in the 1950s and 1960s.

To arrive at new estimates of NNS and cost effectiveness, the Boston-based researchers constructed a Markov computer model that simulates the clinical progression of a cohort of patients, can integrate a wide array of parameters and allows the analysts to plug in different estimates to determine which are most important in determining outcomes.

In addition to the old and new estimates of reactivation rates, the group included in their model estimates based on published reports of TB mortality, percent of diagnosed patients who complete isoniazid (INH), the standard therapy for LTBI (for U.S.-born residents, 50 percent; for foreign-born, 48 percent) and the effectiveness of the therapy among those who complete it.

"The take home message of this research," Dr. Linas said, "is not that we should reduce funding for LTBI screening, but that we can use current funding to make greater strides toward eliminating TB by targeting those at highest risk for latent infection becoming active."

Source: American Thoracic Society (news : web)

Related Stories

Recommended for you

Creation of synthetic horsepox virus could lead to more effective smallpox vaccine

January 19, 2018
UAlberta researchers created a new synthetic virus that could lead to the development of a more effective vaccine against smallpox. The discovery demonstrates how techniques based on the use of synthetic DNA can be used to ...

Study ends debate over role of steroids in treating septic shock

January 19, 2018
The results from the largest ever study of septic shock could improve treatment for critically ill patients and save health systems worldwide hundreds of millions of dollars each year.

New approach could help curtail hospitalizations due to influenza infection

January 18, 2018
More than 700,000 Americans were hospitalized due to illnesses associated with the seasonal flu during the 2014-15 flu season, according to federal estimates. A radical new approach to vaccine development at UCLA may help ...

Flu may be spread just by breathing, new study shows; coughing and sneezing not required

January 18, 2018
It is easier to spread the influenza virus (flu) than previously thought, according to a new University of Maryland-led study released today. People commonly believe that they can catch the flu by exposure to droplets from ...

Zika virus damages placenta, which may explain malformed babies

January 18, 2018
Though the Zika virus is widely known for a recent outbreak that caused children to be born with microencephaly, or having a small head, and other malformations, scientists have struggled to explain how the virus affects ...

Certain flu virus mutations may compensate for fitness costs of other mutations

January 18, 2018
Seasonal flu viruses continually undergo mutations that help them evade the human immune system, but some of these mutations can reduce a virus's potency. According to new research published in PLOS Pathogens, certain mutations ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.