NWT RESEARCH DATABASE

Regions: Inuvialuit Settlement Region, Gwich'in Settlement Area, Sahtu Settlement Area, Dehcho Region, North Slave Region, South Slave Region

Tags: health, genetics, tuberculosis, epidemiology

Objective(s): To quantitatively review epidemiological links established in this study between identical genotypes and conventional contact tracing for direct transmission exposure.

Project Description: The questions posed are: 1. Did genotyping identify unknown TB contacts or transmissions among cases studied? Examination of the genotype of each isolate of M. tuberculosis from reported cases in the NWT may identify epidemiological links among the studied cases not previously identified through conventional contact tracing. The study will quantitatively review epidemiological links established in this study between identical genotypes and conventional contact tracing for direct transmission exposure. As each strain of M. tuberculosis has a unique genotype, TB cases with identical genotypes will be assumed to be linked and treated as clusters. My hypothesis is that TB cases with identical genotypes will also be linked through the general concept of transmission using the concentric circle model. The principles used to determine what concentric circle a contact fits into depends on the amount of bacteria the case was spewing into the air, the proximity (closeness) of airspace and the duration or length of time the case and contact shared airspace. Genotyping will be explored as a contact tracing tool along with the conventional contact tracing method. 2. Are specific risk factors related to demographics, risk behavior, and TB history such as: age, gender, home community, employment, ethnicity, excessive alcohol consumption, IV drug use, HIV, known record of untreated latent TB infection (LTBI), date of diagnosis, and known contact with a case associated with clustering of genotypes? My hypothesis is that M. tuberculosis clusters will be associated with some of the listed factors, which will help target future case finding in the NWT. Basis for this hypothesis relates to known causal relationships between risk factors and development of tuberculosis. Secondary data will be used in this study, which is stored either on paper or electronically at the Office of the Chief Public Health Officer (OCPHO), Government of the NWT. The epidemiology data has been collected by the OCPHO using an enhanced surveillance form called “TB Assessment Form` (enclosed), which includes the specific risk factors for study. The ``TB Assessment Form`` is completed by primary care providers, usually by a community health nurse in a remote community or infection control nurse or public health nurse in larger communities. Staff at the OCPHO will extract the electronic data, the specific epidemiology data outlined in this study and provide non-identifiable line listing in Excel format to the principle investigator. The line listing will include a unique laboratory number for purposes of matching DNA fingerprints (genotypes). The genotypes for each culture confirmed case in the study period and unique laboratory number will be provided by the molecular biologist at Alberta Provincial Laboratory. The extracted data will be stored on a confidential data drive with user code access. This study will be the first time all known genotypes will be examined, correlated, and now studied using specific risk factor correlation. DNA fingerprinting is done in batches by a molecular biologist at the Provincial Laboratory in Edmonton Alberta, who analyses each DNA fingerprint pattern using Bionumerics software, reporting the isolates in groupings with identical DNA fingerprints. All DNA fingerprint analysis and isolates are stored at the Provincial Laboratory. Coordination will include aligning or grouping the DNA fingerprints into dendrograms to assist with analysis. Statistical analysis will include correlation between M. tuberculosis isolate genotype of a single TB case with specific risk factors. Genotyping will be a dependent variable while the demographic, social risk variables and TB history will be independent variables. The demographic variables for each TB case will include home community at diagnosis, age, gender and year of diagnosis. Variables that will be analyzed as risk factors associated with genotype clusters will be: excessive alcohol consumption, Aboriginal, HIV test result, homeless status, employment status, and TB history will include prior contact with a case, and previous LTBI. Univariate analysis will include frequencies for all dependent and independent variables. Bivariate analysis will be performed to establish relationships between the two largest genotype clusters with the highest frequencies with the independent variables. Statistical significance, p <.05, will be used to infer statistical relationship. The statistical significance will allow generalization of tuberculosis population studied in the NWT. Research findings will be shared with the Department of Health and Social Services Tuberculosis Programme. Conclusions from this study may provide specific guidance in methods to control spread of this infectious disease. This data will be summarized in EpiNorth, a Government of Northwest Territories publication and a submission will be sent to the journal titled, The International Journal of Tuberculosis and Lung Diseases. If accepted, this data may be presented at international conferences. Conclusions from this study will be considered for incorporation into the Northwest Territories Tuberculosis Manual, as guidelines for disease control. The fieldwork for this study will be conducted from March, 2010 to December 31, 2010.