[Latent tuberculosis infection (LTBI): What happens at 5 years of the 155 LTBI recent contacts of tuberculosis with positive microscopic examination?].

INTRODUCTION

Contacts of individuals with tuberculosis are at risk of latent infection (LTBI), which can progress to active tuberculosis. The aim of the study was to determine the incidence of tuberculosis in contacts and its risk factors in subjects with LTBI.

METHODOLOGY: This retrospective study from the tuberculosis control centre in Guadeloupe identified smear-positive tuberculosis cases and their contacts. We estimated the incidence of tuberculosis at 5 years using the Kaplan Meier method and identified risk factors for tuberculosis occurrence among contacts by a Cox model.

RESULTS

We analysed 292 contacts of 73 individuals with smear-positive tuberculosis between 2008 and 2015. Of these, 155 contacts had LTBI and 8 developed tuberculosis. The risk of developing tuberculosis was 11.5% (CI : 4.3%-23.4%) for untreated subjects and 1.9% (CI: 0.23%-6.8) for treated subjects. Risk factors identified for tuberculosis were: bacillary density of the index case (HR: 9.10, CI: 1.7-48.4), previous BCG (HR: 0.06, CI: 0.01-0.34), and treatment of LTBI (HR: 0.08, CI: 0.01-0.49).

CONCLUSIONS

This study confirms the relevance of treating LTBI in the context of recent contagion but also the benefit of a BCG vaccination.