High incidence of latent tuberculous infection among South African health workers: an urgent call for action

• Published in: The international journal of tuberculosis and lung disease 2015-06, Vol.19 (6), p.647-653
• Main Authors: McCarthy, K. M., Scott, L. E., Gous, N., Tellie, M., Venter, W. D. F., Stevens, W. S., Van Rie, A.
• Format: Article
• Language: English
• Subjects: Adult; Female; Health Personnel; Humans; IGRA; Incidence; Infection Control - methods; Infectious Disease Transmission, Patient-to-Professional - prevention & control; Interferon-gamma Release Tests; Latent Tuberculosis - diagnosis; Latent Tuberculosis - epidemiology; Latent Tuberculosis - microbiology; Latent Tuberculosis - prevention & control; Latent Tuberculosis - transmission; Male; Middle Aged; Mycobacterium; Occupational Exposure - adverse effects; Occupational Exposure - prevention & control; Occupational Health; Predictive Value of Tests; Prospective Studies; Risk Factors; South Africa - epidemiology; Students, Medical; Tb Infection Control; Time Factors; Tst; Tuberculin Test; Workload; Young Adult
• ISSN: 1027-3719; 1815-7920
• DOI: 10.5588/ijtld.14.0759

SETTING: In South Africa, health care workers (HCWs) are at two-fold greater risk of acquiring tuberculosis (TB) disease than the general population. Few studies have evaluated the risk of incident tuberculous infection.OBJECTIVE: To determine the incidence and risk factors for latent tuberculous infection (LTBI) among HCWs and to compare the results of the interferon-gamma release assay (IGRA) with those of the tuberculin skin test (TST).DESIGN: HCWs, including medical students, underwent a TST and human immunodeficiency virus (HIV) and IGRA testing at baseline and 12 months, and IGRA at 6 months. The participants kept 12-month TB exposure logs.RESULTS: Among 199 participants (150 [76%] females, median age 31 years [range 20-61]), incident LTBI was documented using IGRA in 25/97 (26%; incident rate 29 cases/100 person-years [py], 95%CI 20-44) and using TST in 25/93 (27%; incident rate 29 cases/100 py, 95%CI 19-42). Agreement between TST and IGRA was poor (44.8%, κ = 0.23). Higher annual exposure to TB cases was reported among persons with LTBI than in those who were persistently IGRA-negative (81 cases, 95%CI 61-102 vs. 50 cases, 95%CI 43-57, P < 0.01).CONCLUSION: The high LTBI incidence and the association of incident LTBI with annual TB caseload among HCWs indicate that more effective TB infection control should be implemented in South African health care facilities.