Tuberculosis incidence among infected contacts detected through contact tracing of smear-positive patients

Abstract

Background The contacts of people with pulmonary tuberculosis (PTB) have a high risk of becoming infected and developing tuberculosis (TB). Our aim was to determine the incidence of TB and its risk factors in a cohort of contacts with latent TB infection (LTBI) detected through contact tracing of smear-positive PTB cases. Methods and findings We performed a population-based retrospective cohort study including contacts that had LTBI, and were contacts of people with PTB who started treatment between 2008 and 2014. We followed up contacts until they developed TB or until the end date for follow-up (31st December 2016). We used Kaplan-Meier curves to compute incidence at 2 and 5 years, and Cox regression to compute hazard ratios (HR) and their 95% confidence intervals (CI). We analyzed 3097 close contacts of 565 PTB cases. After exclusion of 81 co-prevalent TB cases, 953 contacts had LTBI, of which 14 developed TB. Their risk of developing TB after two and five years was 0.7% (CI: 0.3–1.6) and 1.8% (CI: 1.1–3.1) respectively. Contacts who had not been referred for LTBI treatment had a 1.0% (CI: 0.2–4.0) risk at 5 years. Risk of developing TB at 5 years was 1.2% (CI: 0.5–3.0) among people who completed treatment, and 11.1% (CI: 5.1–23.3) for those who did not. Risk factors for TB were not completing LTBI treatment (HR 9.4, CI: 2.9–30.8) and being female (HR 3.5, CI: 1.1-11-3). Conclusions LTBI treatment plays a fundamental role in decreasing the risk of developing TB. It is necessary to achieve a maximum contact tracing coverage and the highest possible compliance with LTBI treatment.

Effectiveness of Preventive Therapy for Persons Exposed at Home to Drug-Resistant Tuberculosis, Karachi, Pakistan

“…By using the pooled relative risk, we estimated the effectiveness of preventive therapy to be 72%. This estimate is comparable to the effectiveness that we found by using incidence rate data from other studies ( 22 , 25 – 27 ) and gives more confidence in interpretation of our results. Of note, these studies also had some of the limitations highlighted previously.…”

“…We performed the same exercise by using TB incidence rates from 2 other studies and a meta-analysis to demonstrate the potential range of IRR and IRD ( 22 , 26 , 27 ) ( Table 4 ). Equivalent results were achieved by using rates from Reichler et al ( 26 ) and Martin-Sanchez et al ( 27 ); the expected number of TB cases was 6.6 and IRR was 0.29 (95% CI 0.04–1.3). By using rates of TB disease incidence in household contacts of TB patients as determined by Fox et al ( 22 ), we calculated the IRR to be 0.50 (95% CI 0.06–2.8).…”

Implementing contact tracing for tuberculosis in Kyrgyz Republic and risk factors for positivity using QuantiFERON-TB Gold plus

“…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 – 5 ] or T_SPOT® [ 6 ]. 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 – 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 ].…”

“…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 – 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 ].…”

Sex-related differences in smear-positive pulmonary tuberculosis patients in Kuala Lumpur, Malaysia: Prevalence and associated factors

“…This could be due to the higher population density in Kuala Lumpur (7328 km 2 ), which is almost five times higher compared to that of Penang (1692 km 2 ) [ 17 ]. Studies from other countries such as Barcelona, Spain (26.4%) [ 24 ], Hyderabad city in Pakistan (28.3%) [ 9 ] and Almaty, Kostanay, and Kyzylorda city in Kazakhstan (34.3%) [ 25 ] have a relatively lower prevalence of smear-positive. Kuala Lumpur has achieved 100% urbanization with higher population density [ 17 ]; thus, overcrowding and poor living environments, with urban slum problems probably led to a higher prevalence of smear-positive PTB [ 26 ].…”