RATIONALE

The identification and evaluation of persons in close contact with an infectious tuberculosis (TB) patient (contact investigation) has been viewed as an expensive, low-priority endeavour in low- and middle-income countries. Increasing concern about failure to meet case detection targets, with the spread of Mycobacterium tuberculosis to vulnerable people such as children and people with HIV infection and with the transmission of drug-resistant M. tuberculosis, have, however, prompted reassessment of the potential benefits of contact investigation. The goal of this review was to update a systematic review by Morrison et al. published in 2008 (1), that included studies through 2005. In particular, we were interested in examining studies that included information on the drug susceptibility of the index case strain and on the HIV status of the index case and contacts.

METHODS

We conducted a systematic review and meta-analysis to determine the yield of household contact investigation. Two electronic databases (PubMed and Embase) were searched for primary studies from January 2006 through August 2011 with the same search terms as in the previous review: ‘tuberculosis’, ‘Mycobacterium tuberculosis’, ‘contact tracing’, ‘contact investigation’ and ‘household contact.’ The aim of the search strategy was to identify all studies that evaluated the number of cases of active TB or latent tuberculosis infection (LTBI) found when contact investigation was conducted among household members of people with active pulmonary TB (index cases). All published articles on the yield of household contact investigation, including cross-sectional and prospective studies, were included. The language of the publications reviewed was restricted to English.

RESULTS

Nineteen papers were included in the overall analysis. The yield for all TB (bacteriologically confirmed and clinically diagnosed) was 4.51% of contacts investigated; for cases with bacteriological confirmation, the yield was 2.24%. LTBI was found in 50.54% of contacts investigated. For HIV-positive index cases, the yield was 9.41% of contacts investigated; for index cases with multi-drug-resistant (MDR)-TB, the yield was 3.44%.

CONCLUSIONS

The overall results of contact investigations conducted in the past 5.5 years are essentially the same as those found in the earlier review, but the studies provide more information on transmission from HIV-infected index cases and patients with MDR-TB. These findings suggest that contact investigation may improve early case detection and decrease transmission of M. tuberculosis in high-incidence areas. In addition, there should be a focus on evaluating contacts of HIV-positive index cases and on contacts of persons with MDR-TB.

REFERENCE

1.

Morrison J, Pai M, Hopewell PC. Tuberculosis and latent tuberculosis infection in close contacts of people with pulmonary tuberculosis in low-income and middle-income countries: a systematic review and meta-analysis. Lancet Infectious Diseases. 2008;8:359–368. [PubMed: 18450516]