Routine TB screening beneficial in UK cities with high immigrant population

Routinely screening patients for tuberculosis (TB) in general practice in industrialised cities with a high migrant population can increase the detection of active TB and boost levels of TB vaccination, according to a study published in the May 5^th edition of The Lancet. The randomised controlled trials involved 50 general practices in Hackney, east London, an area of social deprivation with a high immigrant population and increasing incidence of TB.

For the past several years there has been an increasing incidence of TB in many industrialised countries, particularly in cities with immigrant populations from settings where there is a high TB prevalence. Although screening as a method of TB control is endorsed in UK guidelines, its value is uncertain and has been criticised as ineffective and unethical.

The UK remains a country with low, but increasing, TB incidence and data regarding the effectiveness of routine screening in low incidence settings are lacking, with policy decisions based upon observational studies and mathematical models. Investigators from academic institutions, hospitals and general practices in London therefore conducted a randomised controlled trial to see if routinely screening patients registering with GPs increased the detection of active TB, latent TB, and boosted rates of BCG TB vaccination in the over-fives.

Between 2002 and 2004 50 GP practices in Hackney were randomised to either offer a TB screen to all new patients as part of an initial health check or to continue to offer the usual standard of care. The TB screen was verbal, involving questions about BCG vaccination status, symptoms of TB, migration history, and contact with TB-infected individuals, and was followed by a tuberculin skin test. If appropriate, patients were then referred for a chest X-ray.

Outreach education was provided to the practices about screening and there was a small financial incentive to participate in the study. Patient information leaflets about TB and TB screening were available in the languages most commonly spoken in Hackney – English, Turkish, Bengali, French and Somali.

Of the 23,500 patients who attended a registration health check at a practice randomised to offer a TB screen, 57% (13,500), actually had a screen.

Only a small number of cases of active TB were diagnosed during the study (66 at the screening practices and 54 at the control practices.

However, patients registering at the practices offering the screens were significantly more likely to have active TB diagnosed than patients registering at control practices (odds ratio: 1.68; p = 0.03).

In addition, patients attending the screening practices were somewhat more likely to have latent TB diagnosed than patients registering with the 25 control surgeries (p = 0.0.055).

The investigators also established that offering the routine TB screen increased seven-fold the proportion of patients aged five and over who received the BCG vaccination (p < 0.001).

“We have shown that an educational outreach programme for promotion of screening for tuberculosis in an inner-city primary health care district improves both diagnostic and preventative activity, increasing the proportion of active and latent tuberculosis cases identified in primary care, and raising BCG coverage”, write the investigators.

They add, “our study location shares features with other UK inner city areas and other European cities with an increasing incidence of tuberculosis.” These include, socioeconomic deprivation, large numbers of foreign migrants, increasing rates of resistance to antimycobacterial drugs, and increasing HIV prevalence.

The investigators therefore conclude, “our study suggests screening could have a clinically beneficial effect, should have useful generalisability, and could be recommended as part of tuberculosis control initiatives in industrialised countries.”