Over a third of TB cases in UK prisons are drug-resistant

Many UK prisoners with tuberculosis have a drug-resistant form of the disease, according to a study published in the Journal of Epidemiology and Community Health.

The research also showed that the majority of tuberculosis (TB) cases in prisoners were potentially infectious. Furthermore, the majority of prisoners did not complete their TB therapy within a year, and over a quarter of those receiving treatment for the infection at the time of their release from incarceration were subsequently lost to follow-up.

“This study found extremely high levels of drug resistance among tuberculosis cases diagnosed while in prison in the UK. Prisoners were also…likely to have infectious form of disease and not complete treatment, with management complicated by transfer, release and social factors”, write the investigators.

The UK is a low TB prevalence country, but incidence of the disease has increased in recent years. Prisoners are one of the groups recognised to have a high risk of the infection.

Moreover, prisoners often have other social and clinical factors that render them more vulnerable to TB and the progression of the disease, such as drug and alcohol abuse, homelessness and HIV infection. Transmission of TB has been reported in UK prisons, and an outbreak of drug-resistant TB in London was linked to imprisonment in many of the cases.

Investigators examined the characteristics of prisoners diagnosed with TB in the UK between 2004 and 2007 and compared them to those of other individuals diagnosed with the infection. Information was also gathered on rates of resistance, treatment outcomes, and on the clustering of infections.

Over the four years of the study, a total of 205 prisoners were diagnosed with TB. This represented less than 1% of the 29,340 TB cases detected during this period.

Prisoners with TB differed from others with the infection in several important respects.

They were more likely to be born in the UK (47% vs. 25%), and to be of black Caribbean (18% vs. 2%) or white ethnicity (32% vs. 22%).

In addition, prisoners were more likely to have pulmonary TB (75% vs. 56%) and for this to be potentially infectious - sputum-smear-positive (69% vs. 57%).

TB that was resistant to at least one drug was detected in 35% of prisoners. Despite constituting only 1% of all TB cases, prisoners account for 4% of all TB diagnoses with resistance to the key first-line drug isoniazid. This increased to 10% when the investigators restricted their analysis to UK-born patients.

Prisoners also had poorer treatment outcomes. Less than half completed their TB therapy within a year (48% vs. 80%), and 21% of individuals were lost to follow-up on their release. More than half (55%) of these patients had a drug-resistant form of the disease.

“The high level of drug resistance and low proportion of prisoners completing treatment within a year is concerning”, comment the researchers.

Although prisoners were less likely than others to die whilst taking TB therapy, the investigators noted that their median age at death was lower than other patients (48 vs. 70 years).

Results from samples obtained from 57 patients showed that 60% of TB cases were clustered.

“Attributing transmission to imprisonment, however, is not possible in this study”, write the investigators. They do nevertheless suggest, “congregate settings of prisons may contribute to transmission.”

The investigators conclude, “high rates of tuberculosis, especially drug-resistant tuberculosis, among prisoners along with low levels of successful treatment mean prisoners represent a particular challenge for tuberculosis control. These findings support national guidance recommending prisoners to be screened on entry, all those on treatment to receive directly observed therapy (DOT), and continuity of care ensured for transferred and released cases”.