Published ahead of print on February 8, 2008, doi:10.1164/rccm.200711-1756OC Am. J. Respir. Crit. Care Med., Volume 177, Number 9, May 2008, 1041-1047 A more recent version of this article appeared on May 1, 2008
Submitted on November 28, 2007 Evaluation of a Model for Efficient Screening of Tuberculosis Contact SubjectsKhaoula Aissa1,1 Service de Pediatrie, Centre Hospitalier Intercommunal de Creteil, Creteil, France, 2 Centre de Lutte Anti-Tuberculeuse, Centre Hospitalier Intercommunal de Creteil, Creteil, France, 3 Association Clinique et Therapeutique Infantile du Val de Marne (ACTIV), Saint Maur, France, 4 Department des maladies infectieuses, Institut de veille sanitaire, Saint Maurice, France, 5 Faculte Necker-Enfants Malades, INSERM U550, Paris, France, 6 Service de Pediatrie, Centre Hospitalier Intercommunal de Creteil, Creteil, France; Unite 841, INSERM, Creteil, France; Faculte de Medecine, IFR10, Universite Paris 12, Creteil, France * To whom correspondence should be addressed. E-mail: christophe.delacourt{at}chicreteil.fr.
Rationale: Contact tracing is an important component of tuberculosis control programs. Standardization of contact investigation protocols can make them more efficient. Objective: To develop a model to select contact subjects for screening. Methods: We prospectively collected standardized data on 325 tuberculosis index cases and their 2009 contacts. Factors that independently influenced the risk of TB infection were included in the model, which was then validated in a second prospective cohort of 88 tuberculosis cases and their 618 contacts. Main results: Eight independent risk factors were identified (OR ; 95% confidence interval) : age, with three subgroups: >=6-15< years (3.6 ; 1.6-8.0), >=15-30< years (3.7 ; 1.8-7.7), >=30 years (4.1 ; 2.0-8.5) ; cavitation on the index case's chest radiograph (1.6 ; 1.1-2.2) ; an index case sputum smear with 100 or more acid-fast bacilli per field (1.8 ; 1.2-2.8); household contact at night (2.1 ; 1.3-3.2); first-degree family relationship with the index case (2.1 ; 1.3-3.3); active smoking by the contact (1.6 ; 1.1-2.4); free health care (2.0 ; 1.2-3.2); and birth in a country with TB incidence rate higher than 25/100 000 (2.2 ; 1.5-3.2). Predictive probabilities were chosen to ensure false-negative rates lower than estimated tuberculosis infection background. The number of contacts to be investigated was reduced by 26% while maintaining a false-negative rate of 8%. Conclusions: This study provides a standardized contact screening model which reduces resources required without negatively affecting disease control. Key words: tuberculosis; contact screening; tuberculin skin test
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