Detecting TB to stop its spread: jails as a case study
24/03/2015 // Specials // Photos: Shutterstock; Andreas Fechner
Tuberculosis control efforts target at-risk populations, including prisoners

Around the world, progressive healthcare system are adopting strategies to interrupt the spread of tuberculosis by screening the most at-risk patient groups to detect infection before it turns into active pulmonary tuberculosis (TB) – which is contagious and potentially deadly.

TB at a glance

According to the World Health Organization (WHO), up to two billion people worldwide carry a latent TB infection. If not treated, five to ten percent of those patients are at risk of developing the active form of the disease during their lifetime.

Subpopulations identified by the WHO as at-risk for developing active disease from latent TB infection include people living with HIV, young children, healthcare workers, certain miners, and those in close quarters such as jails and prisons. Experts also point to diabetes patients, smokers and patients on certain drugs as at-risk for TB.

QIAGEN is partnering with public health experts and healthcare systems to support TB control by providing QuantiFERON-TB Gold (QFT), the modern standard in screening for latent TB infection. As a highly accurate, quantitative blood test evaluated in laboratories, QFT is taking the place of the time-consuming and subjective tuberculin skin test, which is based on 110-year-old technology. Jails and prisons are a case in point for the changing fight against TB.

Globally, prisoners are 11 to 81 times more likely to contract tuberculosis than the general population. With crowded conditions and high-risk demographics, incarceration is characterized by elevated rates of drug-resistant TB and co-morbidity with HIV. Jails also serve as a nexus in the spread of tuberculosis to broader communities.

"Effective TB control in prison protects prisoners, staff, visitors and the community at large."
World Health Organization (

The Dallas County Jail in Dallas, Texas, is acutely aware of the danger of TB to its inmates – and the connection between detainees’ health and that of the surrounding communities. The Dallas metropolitan area has the fifth-highest incidence of TB among U.S. cities.

“With an average inmate population of 6,200, and high turnover because detainees often are released in days, we administer an average of 4,819 tuberculin skin tests per month in our routine healthcare screening of incoming prisoners,” says Dr. Esmaeil Porsa, medical director of the Dallas County Jail. “About 65% of the tests are read by our staff, while 35% of the inmates tested leave before the time comes for a second visit to have the skin tests read.”

An average of 451 chest x-rays are conducted each month by the Dallas County Jail, and an average of seven inmates at any time are treated for active TB in medical isolation cells. Because of the high costs of TB control and treatment, Dr. Porsa and his staff undertook in 2014 to investigate the cost-effectiveness and accuracy of testing methods.


"The IGRA is a quantitative technology yielding results that are 97-99% accurate, unlike the TST, which depends on a subjective reading of the size and texture of the skin reaction."
Dr. Esmaeil Porsa, Medical Director, Dallas County Jail

“Our study took a sample of 500 inmates and investigated both the medical results of TB screening and the costs in time and money for our institution,” Dr. Porsa says. “Our time-motion analysis found the skin tests, which require injecting tuberculin in the skin of the patient’s forearm followed by a second visit two to three days later to examine the reaction, take nearly 10 times as much time for the health care staff as the modern blood test. Custody staff also spends slightly more time on the TST.”

Dr. Porsa says the study also highlighted differences in accuracy between old and new. “The IGRA is a quantitative technology yielding results that are 97-99% accurate, unlike the TST, which depends on a subjective reading of the size and texture of the skin reaction,” he says.

The comparison also found roughly 10% of the TB infections among inmates were missed by the skin tests, Dr. Porsa says. The challenging environment of a city jail, he says, can cause healthcare staff to take shortcuts in evaluating skin reactions, such as looking at forearms through the glass of cell doors, without measuring or running a finger over the area of swelling, as required. These missed opportunities inevitably mean missed active TB cases, he says.

“This poses a danger of spreading TB to fellow inmates, correctional and healthcare personnel, and the broader community,” Dr. Porsa says.

QFT has been clinically proven to be 97 to 99% accurate in detecting TB infection, and the improved diagnostic effectiveness of changing from subjective skin tests to modern lab tests can help prevent contagion by catching all of the infections – in jails and other settings.

Like other healthcare systems worldwide, jails and prisons face limited budgets, with growing costs and competing priorities.

“Correctional executives and medical directors need to look strategically at TB control practices,” says Dr. Porsa, “and consider the cost-effectiveness as well as the health impact of using more accurate, less time-consuming blood tests rather than tuberculin skin tests.”


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