Dépistage de l’infection tuberculeuse latente (ITL) à Paris à l’aide d’un test interféron chez des sujets contact en 2009

[Longitudinal follow-up of contact subjects of cases of tuberculosis in Paris]

AIM

To our knowledge, the proportion of active tuberculosis diagnosed after 12-18 months during a screening tuberculosis process in a specialized centre (centre de lutte antituberculeuse [CLAT]) has not been described in France. The majority of other countries do not have any recommendation to screen at this time.

METHODS

We evaluated the number of treated or not treated latent tuberculosis infections (LTI) identified during tuberculosis screening. We identified the causes of ITL non-treatment, the number of active disease cases and the proportion of subjects lost to follow-up after 12-18 months.

RESULTS

Among the 1066 contact subjects, 159 (15 %) had a positive QuantiFERON-TB-Gold In-Tube(®) test. A prophylactic treatment with Rifinah(®) was given to 97 (61 %) subjects, 7 (7.3 %) having developed side effects that led to treatment interruption. A high proportion (56 %) of contact subjects were lost of follow-up and the main reason for no prophylactic treatment (20/52, 38 %) was due to these losses. No active disease cases were identified among the 474 (44 %) contact subjects who had a chest X-ray after 12-18 months follow-up by the CLAT. The low level of positive QuantiFERON-TB-Gold In-Tube(®) tests (15 %) could be explained by the high specificity of this test and the strong proportion of occupational contacts, of whom a probably significant number were not exposed to active disease.

CONCLUSION

The absence of active disease at 12-18 months and a majority (56 %) of contact subjects lost from follow-up at this period let us propose not to recall contact subjects at 12-18 months with the exception of those living under the same roof as the index case and/or those having a cumulative contact time of greater than 100 hours during the theoretical infectious period. This proposal remains to be confirmed by other studies, particularly including possible secondary cases diagnosed outside the screening periods by the CLAT.