Outcomes of a tuberculosis contact investigation programme in Italy

Abstract

To the Editors: Mycobacterium tuberculosis transmission is affected by several key factors, such as contagiousness of the index tuberculosis (TB) case, immune status and susceptibility of the exposed TB contact, duration and patterns of contact between the index TB case and the exposed TB contact, and characteristics of the environment within which such contact occurs [1–3]. Tracing strategies that allow the early identification and appropriate treatment of TB contacts with latent TB infection (LTBI) or active TB should be a priority of TB control programmes with adequate resources [3, 4]. In agreement with the guidelines laid out by the Italian Ministry of Health, the Piedmont Region has activated and regularly updated TB contact investigation procedures [5]. We used data from the Piedmont Region TB contact investigation programme to assess the role of selected risk factors for TB infection (TBI) among TB contacts in the city of Turin, Italy. For each suspected or confirmed pulmonary TB case, active contact investigation was conducted among household members, close contacts and regular contacts, defined according to the stone-in-the-pond method [6]. Passive investigation was used for occasional contacts [5]. The Piedmont TB notification systems were used to identify pulmonary TB cases between January 2002 and December 2008. TB cases were classified into three categories of contagiousness: 1) sputum smear-positive and culture-positive (acid-fast bacillus positive (AFB+)); 2) sputum smear-negative but culture-positive (CULT+); and 3) sputum smear-negative and culture-negative or not examined, i.e. other than defined (OtD). Interviews were conducted with each TB case to identify TB contacts, defined as anyone having shared air …