Risk of Tuberculosis after Recent Exposure. A 10-Year Follow-up Study of Contacts in Amsterdam

Abstract

Five-year risk of TB among contacts with evidence of infection was higher compared with older estimates, and differed considerably by age. Incidence of TB among contacts with LTBI was low, suggesting limited impact may be expected of expanding preventive therapy.

Numbers needed to treat to prevent tuberculosis

“…Nonetheless, these tests still have a role in helping clinicians improve the health outcomes of their patients and to progress towards TB elimination. Conversely, the negative predictive value of TST and IGRAs is high enough to exclude most individuals who would not benefit from LTBI treatment [5]. Contrary to what Martina Sester and colleagues maintain, the number of active TB cases that will continue to occur among those testing negative is thus unlikely to have a significant public health impact.…”

“…More recently, it has become evident that the risk of the development of tuberculosis among patient groups classically considered at risk is highly variable, and is not necessarily associated with the results of immunodiagnostic testing by the TST or IGRAs [2][3][4][5]. More detailed knowledge of groups at actual risk of tuberculosis and on immunodiagnostic test performance in these risk groups may provide better guidance for physicians on priorities for targeting tuberculosis testing and LTBI treatment in low-incidence countries.…”

“…Although not selected by a systematic approach, we made use of the fact that several studies with large sample sizes from low-incidence countries of tuberculosis were recently published from three major groups classically considered at risk for progression. In these studies, tuberculosis contacts [2,4,5], immunocompromised hosts [3] and healthcare workers [6][7][8] were evaluated for LTBI and subsequent progression. We have calculated the number needed to treat to prevent one case of tuberculosis (table 1), and found that the number needed to treat was very similar across three studies evaluating 1579, 5020 and 4774 tuberculosis contacts, respectively, with a positive TST or IGRA, ranging from 30 to 37 [2,4,5] (table 1).…”

“…In these studies, tuberculosis contacts [2,4,5], immunocompromised hosts [3] and healthcare workers [6][7][8] were evaluated for LTBI and subsequent progression. We have calculated the number needed to treat to prevent one case of tuberculosis (table 1), and found that the number needed to treat was very similar across three studies evaluating 1579, 5020 and 4774 tuberculosis contacts, respectively, with a positive TST or IGRA, ranging from 30 to 37 [2,4,5] (table 1). In immunocompromised individuals with a positive test (n=1537) [3], the number needed to treat to prevent a case was higher and ranged from approximately 50 to 80 (table 1).…”

“…Notably, as incident cases of tuberculosis were mainly HIV positive, the number of HIV-infected persons with a positive test needed to treat was lower (range 14.0-25.5) and tuberculosis cases were only found in patients with ongoing viral replication [3]. It should be emphasised that incident tuberculosis cases also occurred in individuals with negative test results [2,3,5], especially among patients with HIV infection. In patients with chronic renal failure (n=270) or rheumatoid arthritis (n=199), stem cell (n=103) or solid organ transplant recipients (n=197) [3], and healthcare workers (n>15 000) [6][7][8], the number of individuals with LTBI needed to treat to prevent one case could not be calculated because no tuberculosis cases occurred during 2 years of follow up in these cohorts…”