Tuberculosis risk varies with the duration of HIV infection: a prospective study of European drug users with known date of HIV seroconversion.

BACKGROUND

It is not known whether the risk of active tuberculosis disease varies with the length of time that individuals are infected with HIV.

OBJECTIVE

To study how, independently of CD4 T cell count, the risk of tuberculosis varies with the duration of HIV infection.

METHODS

Using Poisson regression analysis, the incidence of and risk factors for tuberculosis were studied in 683 injecting drug users (IDU) with a documented date of HIV seroconversion followed in seven cohorts in six European countries until 1998.

RESULTS

Overall incidence was 11.5/1000 person-years. Adjusted for CD4 T cell count and geographic region, the risk ratio (RR) for tuberculosis (both pulmonary and extrapulmonary), compared with the first 3 years of HIV infection, was 2.8 for years 4 to 6 of HIV infection [95% confidence interval (CI), 1.3-6.3], 1.2 for year 7 to 9 (95% CI, 0.3-4.2) and 4.6 after 9 years (95% CI, 1.4-15.0). The adjusted RR for geographic region was 13.1 (95% CI, 4.3-40.0) for Amsterdam and 15.8 (95% CI, 4.8-52.0) for the Valencian region of Spain compared with all other sites combined.

CONCLUSION

The risk of tuberculosis is increased relatively early in HIV infection (year 4 to 6) and also later (after year 9) with possibly a relatively silent period between. As expected, IDU in Southern Europe have a substantially higher risk of tuberculosis than IDU in Northern and Central Europe. Amsterdam forms an exception for Northern Europe, with very high incidence rates.