Tests on immigrants 'miss most TB'

Screening procedures for tuberculosis in immigrants in the UK are missing the majority of cases, new research has revealed.

Using new blood checks rather than chest X-rays would detect over 90% of imported latent TB, experts said, as opposed to the current failure to detect more than 70% of cases of latent infection.

A team of researchers at Imperial College London said new methods of blood testing would mean that people with imported latent TB could be given a course of antibiotics to prevent them from developing an active form of the disease.

TB is caused by a bacterial infection which is normally asymptomatic, but around one in 10 infections leads to active disease, which attacks the lungs and kills around half of people affected.

The incidence of TB has risen dramatically in Britain over the last decade, particularly because of a 98% increase in cases among people who move to the country from overseas, the research said.

Current UK policy requires all immigrants from countries with a TB incidence higher than 40 in 100,000 people per year to have a chest X-ray on arrival to check for active TB, although very few immigrants have the active disease on arrival.

However, a substantial proportion of immigrants are carriers of latent TB which, though initially silent and non-infectious, often progresses to full-blown TB within a few years of arrival in the UK, researchers said.

Professor Ajit Lalvani, director of the Tuberculosis Research Unit at Imperial College London, who led the study, said: "By treating people at that early stage, we can prevent them from developing a serious illness and becoming infectious.

"Crucially, this wider screening could substantially reduce TB incidence while remaining cost-effective. Our findings provide the missing evidence-base for the new national strategy to expand immigrant screening."

His research, which was funded by the Wellcome Trust and the Medical Research Council, analysed results from over 1,200 recent immigrants at centres using new blood tests to screen for latent TB in London, Leeds and Blackburn.

The study found that a fifth of recent immigrants from the Indian Subcontinent and almost 30% from Sub-Saharan Africa are carriers of latent TB and that national screening policy, which does not include immigrants from the Indian Subcontinent, has been missing 70% of imported latent TB.

A Department of Health spokesman said: "Tuberculosis is a global problem and sustained action is needed to detect, diagnose and treat cases earlier.

"We are funding TB Alert, the UK's national TB charity, to increase awareness of TB among primary healthcare professionals and the public.

"We are pleased that this research backs up the latest Nice (National Institute for Health and Clinical Excellence) guidance on TB screening. We expect the local NHS to consider the best ways of tackling this issue in their area."