Abstract
BackgroundEffective active case finding (ACF) activities are essential for early identification of new cases of active tuberculosis (TB) and latent TB infection (LTBI). Accurate diagnostics as well as the ability to identify contacts at high risk of infection are essential for ACF, and have not been systematically reported from Central Asia. The objective was to implement a pilot ACF program to determine the prevalence and risk factors for LTBI and active TB among contacts of individuals with TB in Kyrgyz Republic using Quantiferon-TB Gold plus (QuantiFERON).MethodsAn enhanced ACF project in the Kyrgyz Republic was implemented in which close and household (home) contacts of TB patients from the Issyk-Kul Oblast TB Center were visited at home. QuantiFERON and the tuberculin skin test (TST) alongside clinical and bacteriological examination were used to identify LTBI and active TB cases among contacts. The association for QuantiFERON positivity and risk factors were analysed and compared to TST results.ResultsImplementation of ACF with QuantiFERON involved close collaboration with the national sanitary and epidemiological services (SES) and laboratories in the Kyrgyz Republic. From 67 index cases, 296 contacts were enrolled of whom 253 had QuantiFERON or TST results; of those 103 contacts had LTBI (positive TST or IGRA), and four (1.4%) active TB cases were detected. Index case smear microscopy (OR 1.76) and high household density (OR 1.97) were significant risk factors for QuantiFERON positivity for all contacts. When stratified by age, association with smear positivity disappeared for children below 15 years. TST was not associated with any risk factor.ConclusionsThis is the first time that ACF activities have been reported for Central Asia, and provide insight for implementation of effective ACF in the region. These ACF activities using QuantiFERON led to increase in the detection of LTBI and active cases, prior to patients seeking treatment. Household density should be taken into consideration as an important risk factor for the stratification of future ACF activities.
Highlights
Effective active case finding (ACF) activities are essential for early identification of new cases of active tuberculosis (TB) and latent TB infection (LTBI)
Household density should be taken into consideration as an important risk factor for the stratification of future ACF activities
Active TB is diagnosed based on clinical symptoms, radiological signs and bacteriological confirmation, whereas LTBI is only detectable by indirect immunological tests such as the Tuberculine Skin Test (TST) or interferon-gamma release assays (IGRA) like the Quantiferon-TB Gold plus (QuantiFERON) [3,4,5] or T_SPOT® [6]
Summary
Effective active case finding (ACF) activities are essential for early identification of new cases of active tuberculosis (TB) and latent TB infection (LTBI). The objective was to implement a pilot ACF program to determine the prevalence and risk factors for LTBI and active TB among contacts of individuals with TB in Kyrgyz Republic using Quantiferon-TB Gold plus (QuantiFERON). The World Health Organization (WHO) estimates that about 1.8 billion people are latently infected and that they have a 5–15% lifetime risk of developing TB disease [2]. Public health authorities use contact investigation and active case finding (ACF) to investigate individuals at risk for acquiring infection from an infectious TB patient (index case) [7,8,9]. ACF allows for the detection of TB cases prior to individuals seeking treatment, resulting in earlier treatment and decreasing the number of transmission events [7, 9, 10]
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