The evidence for and utility of current contact tracing methods for tuberculosis in congregate locations in low incidence settings

Braganca Menezes, Darryl A. (2023). The evidence for and utility of current contact tracing methods for tuberculosis in congregate locations in low incidence settings. University of Birmingham. Ph.D.

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Abstract

Introduction: Tuberculosis is a global threat. While numbers are lower in the UK, disease persists and in order to achieve WHO targets of elimination, latent infection needs to be aggressively sought after and treated. In order to facilitate this, we need an effective contact tracing approach. I aim to examine the evidence behind current contact tracing approaches and examine their utility in the current low incidence setting, with a particular focus on congregate settings.

Methods: Data was gathered through the interrogation of Public Health England (PHE) statutory data collection augmented by local chest clinic data which are both collected from confirmed TB patients and subsequent contact tracing efforts. Literature reviews were conducted using established systematic review processes. Further analytical work was conducted as needed using statistical software (STATA/SE 16).

Results: Chapter 1 provides the context for this thesis, discussing tuberculosis as a clinical entity. Chapter 2 demonstrates the evolution of contact tracing and the highlighting how the process was established in a high prevalence environment and how this may no longer apply to the lower incidence setting. Chapter 3 and 4 examine the evidence based behind risk factors in congregate settings as well as the comparative evidence for current contact tracing methods and the availability and utility of others. Chapter 5 summarises the data set, providing outcome data for large scale contact investigations. In chapter 6 I examine the longer-term impact of our current contact tracing approach employing recently available whole genome sequencing data. Using the data set, I derive a prediction model in order to predict TB disease with the variables to hand. Finally, in chapter 8 I address the key aims of this thesis and to what extent I have answered these questions.

Discussion: Our current contact tracing approach while effective in a higher disease prevalence setting, does not allow us to effectively curtail the on-going TB epidemic in a low incidence, congregate setting environment. This approach is resource intensive and we can see that on-going propagation of transmission chains occur. This is largely due to the lack of identified contacts as well as the inability to effectively engage them in the contact tracing process. There is little evidence to support the use of other contact tracing processes. Largely due to the lack of this area having been examined in relation to TB spread in low incidence settings. In addition, the predictive modelling suggests that congregate settings are in themselves, heterogeneous locations that do not possess the same risk factors for individuals who acquire disease. Moving forward, teams involved in Tb prevention and contact tracing need to adopt an approach which can demonstrate relationships and contact status to a higher resolution and this will likely involve a form of social network analysis. More work on inputting prediction model outputs into a risk assignment score can help preventative services prioritise cases for follow up preventing individuals propagating disease chains.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):