U.K. revisits x-ray vans for TB screening

January 5, 2005

Chest x-ray tuberculosis screening vans look likely to return to U.K. streets after a 40-year hiatus. The mobile units would target known TB “hot spots” in a bid to accelerate detection and treatment of the highly contagious disease.

Chest x-ray tuberculosis screening vans look likely to return to U.K. streets after a 40-year hiatus. The mobile units would target known TB "hot spots" in a bid to accelerate detection and treatment of the highly contagious disease.

A pilot trial of a mobile x-ray van among high-risk groups has demonstrated its ability to find cases of active - and hence infectious - TB. Results of the study were presented in November at the British Thoracic Society meeting in London. Government health officials have requested that the technology be evaluated for possible nationwide rollout.

Prompt TB detection and monitoring is problematic because incidence is clustered among individuals with poor access to health and social services such as prisoners, asylum seekers, and the homeless. Identification of TB is also complicated by the high prevalence of drug users, alcoholics, and heavy smokers within these population groups. Classic signs - coughing, night sweats, and weight loss - may be shared by the whole group, while skin tests could be hard to interpret.

Chest radiography is an effective method of spotting active TB. And the use of mobile units means that health professionals can diagnose difficult-to-reach individuals on the spot, according to Dr. Alastair Story, a researcher with the U.K. Health Protection Agency's Communicable Disease Surveillance Centre.

"Sometimes you are only going to get one chance at screening," he said. "You can make the diagnosis there and then, with the person right there. You can tune your index of suspicion to a level where you are not inundating the local services with unnecessary referrals."

Story and colleagues borrowed a digital mobile x-ray van for their trial from the Netherlands, where radiography-based TB screening is routine for populations with an incidence over 50 per 100,000. The DR unit produces far less radiation than systems used in vans of the 1950s and 1960s and around 1/10 of a conventional chest x-ray.

The team acquired 577 chest x-rays from men at three London hostels, two drop-in centers, and a prison and referred 23 cases for further investigation. Three of these turned out to be active TB. This equates to a TB rate of 520 per 100,000, compared with the national rate of 13 per 100,000.

The U.K. department of health is now funding a complete evaluation of the role of digital x-ray vans in TB screening. Assessment will focus on ability of targeted chest radiography to help control infection rates, economic viability, impact of likely referrals on local chest clinics, and acceptability to the target population.

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