Incidence of Latent Tuberculosis Infection in South African Health Care Workers: A Systematic Review

Objective: Tuberculosis (TB) is a major cause of morbidity and mortality in South Africa. Health care workers (HCWs) are at the forefront of the epidemic and are exposed to TB in their communities and as an occupational hazard. The evidence on the risk of infection among HCWs in South Africa is uncertain. The objective of this systematic review is to synthesize the literature focused on describing the incidence of LTBI among HCWs in South Africa based on screening with tuberculin skin test (TST) or interferon gamma release assay (IGRA). Methods: A literature search of PubMed and Embase databases was conducted to identify studies assessing the incidence of TST positivity in South African HCWs on 2/25/2015. The key question of this review was to determine the conversion rate of LTBI in South African HCWs as measured by TST or IGRA tests. A single reviewer selected studies for inclusion based on pre-specified criteria. Cohort studies examining the incidence of LTBI as measured by TST or IGRA conducted in South Africa or in neighboring countries were eligible. The risk of bias was assessed for the included studies. The studies were analyzed qualitatively to address the limited number of available studies as well as the heterogeneity between studies. Results: A total of three prospective cohorts were included. Two of the studies were conducted in South Africa in the cities of Cape Town and Johannesburg. The third study took place in the neighboring country of Zimbabwe. The sample size of these studies ranged from 505 to 199 HCWs. The studies included a diverse array of HCWs from both community clinic and hospital settings. The conversion rate was measured by different methods across studies. For TST, the rate ranged from 19.3 conversions per 100 person-years of follow up to a 38 percent annual incidence rate across studies. The conversion rate for IGRAs had a more narrow range over 12 months: 22 to 26 percent across two studies.