Prevalence of Latent Tuberculosis Infection among Health Workers Resident in Akwa Ibom State, South-South Nigeria

Background: Tuberculosis (TB) remains a Public health problem in Nigeria and Healthcare workers (HCWs) are at risk of Latent Tuberculosis Infections (LTBI) and TB disease. There has been no available information on the prevalence of LTBI in HCWs in Akwa Ibom State especially in hospitals for pulmonary diseases. With Interferon-gamma release assays (IGRA), a new method for diagnosis of LTBI, accurate data on prevalence of LTBI among HCWs could be obtained for infection control measures.

Objectives: The study was designed to estimate prevalence of LTBI among 609 HCWs in hospitals for Pulmonary Diseases that routinely screen for TB infection.

Methods: LTBI was assessed by the QuantiFERON-Gold In-Tube (QFT-IT). Information on gender, age, workplace, job title, BCG vaccination and history of both for potential risk factors for LTBI were obtained from standard questionnaires and analysed using SPSS version 17 (SPSS Inc, Chicago, Illinois).

Results: The prevalence of LTBI was 24.8% and 45.8% as assessed by QFT-IT and TST respectively. In HCW younger than 30 years LTBI prevalence was 9.1% and in those older than 50 years, it was 51.3%. Ward Orderlies and Laboratory staff showed higher prevalence rate than other HCWs (31.4% to 33.8%). The putative risk factors for LTBI were age (>50 year OR 10.53, 95% CI 4.77–23.23), working for ≥ 11 years (OR 11.27% CI 3.5–36.34) and working as Ward Orderly and as Lab staff.

Conclusion: Prevalence of LTBI assessed by QFT-IT is high. This indicates a high infection risk especially in health care workers. Laboratory staff and ward orderlies as well as being in service for >10 years, were more significantly associated with LTBI. The higher LTBI prevalence rate in older HCWs might be due to the cohort effect or the longer time at risk. The difference in prevalence of LTBI between TST and QFT may be due to non-tuberculous mycobacterium (NTM). This may have grave implications of drug toxicity and development of resistance to anti-TB drug among individuals harbouring NTM, but receiving anti-TB medication.