Abstract
Benjamin R. Underwood, Veronica L. C. White, Tim Baker, Malcolm Law
and John C. Moore-Gillon
Background The aim of the study was to investigate the
relative effectiveness of four strategies in detecting and preventing
tuberculosis: contact tracing of smear-positive pulmonary
disease, of smear-negative pulmonary disease and
of non-pulmonary disease, and screening new entrants.
Methods An analysis of patient records and a TB database
was carried out for an NHS Trust-based tuberculosis service
in a socio-economically deprived area. Subjects were contacts
of all patients treated for TB between 1997 and 1999.
New entrants were screened in 1999. Outcomes measured
were numbers of cases of active tuberculosis detected and
numbers of those screened given chemoprophylaxis.
Results A total of 643 contacts of 227 cases of active TB were
seen, and 322 new entrants to the United Kingdom. The highest
proportion of contacts requiring full treatment or chemoprophylaxis
were contacts of smear-positive index cases (33
out of 263 contacts; 12.5 per cent). Tracing contacts of those
with smear-negative pulmonary tuberculosis (12 out of 156;
7.7 per cent) and non-pulmonary disease (14 out of 277;
6.2 per cent) was significantly more effective in identifying
individuals requiring intervention (full treatment or chemoprophylaxis)
than routine screening of new entrants (10 out
of 322; 3.1 per cent).
Conclusions Screening for TB of new entrants to the United
Kingdom is part of the national programme for control and
prevention of TB, whereas tracing contacts of those with
smear-negative and non-pulmonary disease is not. This study
demonstrates that, in our population, the contact-tracing
strategy is more effective than new entrant screening. It is not
likely that the contacts have caught their disease from the
index case, but rather that in high-incidence areas such as
ours such tracing selects extended families or communities at
particularly high risk.
Keywords: tuberculosis, contact tracing, immigrants, cost
effectiveness
Contact tracing and population screening for tuberculosis – who should be assessed?