Evaluation of a large scale tuberculosis contact investigation in The Netherlands (2005)

¹ European Programme for Intervention Epidemiology Training (EPIET), and Dept of Infectious Disease Epidemiology, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands. Current affiliation: Norwegian Institute of Public Health, Oslo, Norway
² Municipal Health Service (GG&GD) Utrecht, The Netherlands
³ Municipal Health Service (GGD) Midden-Nederland, Zeist, The Netherlands
⁴ KNCV Tuberculosis Foundation, The Hague, The Netherlands
⁵ Dept of Infectious Disease Epidemiology, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands
⁶ KNCV Tuberculosis Foundation, The Hague, and Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, Amsterdam, The Netherlands

^* To whom correspondence should be addressed. E-mail: cobelensf{at}kncvtbc.nl.

	Abstract

To evaluate yield and effectiveness of a large-scale contact investigation around a supermarket employee with infectious tuberculosis.

Supermarket customers were screened by tuberculin skin test (TST) and/or X-ray depending on individual characteristics. We estimated the number of recent infections identified based on historical reference data after correction for false-positive TST results.

TST screening (n=15,518) yielded 12 cases of tuberculosis disease as direct result of the investigation (1293 screenings per case identified). X-ray screening (n=5945) yielded no case. There were 359 (2.6%) positive TSTs; 117 (34%) were estimated to be due to recent exposure. The number of customers screened in order to find one case of recent infection was 114, varying from 43 for customers who visited the supermarket twice per week or more, to 4148 for customers who visited less than once per month.

Although this patient probably transmitted M. tuberculosis to at least 117 customers, the contact investigation was inefficient as large numbers of customers had to be screened and the majority of identified tuberculosis infections were probably not related to the index cases. The efficiency could have been improved by omitting X-ray screening and limiting TST screening to customers who reported frequent supermarket visits.