Academic journal article Central European Journal of Public Health

Assessing the Prevalence of Latent Tuberculosis among Health Care Providers in Zagazig City, Egypt Using Tuberculin Skin Test and Quantiferon-Tb Gold In-Tube Test

Academic journal article Central European Journal of Public Health

Assessing the Prevalence of Latent Tuberculosis among Health Care Providers in Zagazig City, Egypt Using Tuberculin Skin Test and Quantiferon-Tb Gold In-Tube Test

Article excerpt

INTRODUCTION

Tuberculosis remains an important public health problem in Egypt. Egypt is ranked among the mid-level incidence countries, with TB prevalence reported by the World Health Organization (WHO) to be 29 per 100,000 population in 2013 (1). Tuberculosis is an occupational disease often detected among health care providers. Their continuous exposure to tuberculosis patients together with working in poorly ventilated spaces make them more vulnerable to the risk of infection (2). Once the infection with tuberculosis bacilli occurred, active disease develops in about 10% of cases. The remaining 90% stays in a state of latent tuberculosis infection (3).

Diagnosis of latent tuberculosis infection aims mainly at providing early treatment of the condition to prevent the development of active tuberculosis. Yet, it has been held back by the lack of a gold standard test due to the low number of dormant tubercle bacilli, not directly detectable or quantifiable. Latent tuberculosis infection results in an asymptomatic state with no clinical or radiological evidence of active tuberculosis but with survival of inactive bacilli in tissues (4).

For more than 100 years, Tuberculin skin test was the only method available for the diagnosis of latent tuberculosis infection (5). With the advances in the field of genomics and immunology, new diagnostic tests named QuantiFERON®-TB Gold In-Tube have emerged. They are characterized by higher specificity than the Tuberculin skin test (6). Using these tests reduced the risk of latent tuberculosis infection overestimation (due to cross-reactions with BCG vaccination or exposure to environmental mycobacteria). This made the investigations of people repeatedly exposed to tuberculosis (e.g. health care providers) more feasible (7).

The asymptomatic nature of latent tuberculosis infection, a lack of accurate diagnostic test and the relatively high cost of using QuantiFERON-TB Gold In-Tube Test (QFT-GIT) appeared as obstacles in many healthcare facilities in developing countries leading to overlooking the disease and its risk factors among health care providers especially those serving immunecompromised patients (8). The objectives of the study were to assess the prevalence of latent tuberculosis infection among health care providers, to compare QFT-GIT and Tuberculin skin test in diagnosis of latent tuberculosis and to determine the associated risk factors.

MATERIALS AND METHODS

Design and Settings

A cross-sectional study was carried out during the period of 6 months (August 2012 - January 2013) in Chest Hospital (the only specialized hospital for tuberculosis in our district) and Nephrology Unit (where immune-compromised patients are treated with dialysis and where cases of tuberculosis were previously detected in this group of patients) at Zagazig University Hospitals, Zagazig city, Egypt.

Subjects and Sampling Technique

Our subjects were nurses and laboratory technicians as they are at greater risk of TB infection due to their direct contact with patients and their specimens (9). Sample size calculation using the EPI info version 6 was carried out depending on the total number of nurses and laboratory technicians during the study in the selected places. From the total of 231, 157 were nurses in Chest Hospital, 56 nurses in Nephrology Unit and 18 Chest Hospital's laboratory technician. The prevalence of latent tuberculosis infection among nurses and laboratory technicians found in the pilot study was 10.6%, at 95% confidence interval and a power of 80.0%. Depending on that 132 randomly selected nurses and laboratory technicians were recruited for this study by stratified random technique from both hospital settings. The final sample included 76 nurses who were in contact with tuberculosis patients (Chest Hospital), 40 nurses who were in contact with immunecompromised patients (Nephrology Unit) and 16 laboratory technicians responsible for laboratory analysis of specimens of tuberculosis patients (Chest Hospital). …

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