Abstract
Background:
It is widely acknowledged that the eradication of H. pylori, a bacterium that can infect the stomach lining, can reduce the risk of stomach cancer. There have been declining incidence rates in stomach cancer and worldwide prevalence of H. pylori over the past few decades but inequities, especially ethnic inequities, remain. Changes in guidelines and introducing new strategies, such as screening programmes, may further reduce infection and inequities. However, there is limited research on New Zealand's management of H. pylori.
Objectives:
This thesis aims to critically examine New Zealand's management of H. pylori with a particular focus on patterns by ethnicity. Research questions were presented for the quantitative analysis:
For the total New Zealand population:
1.
What were the rates of stomach cancer and peptic ulcer disease hospitalisations in Māori, Pacific people, Asian people, and sole European New Zealand health service users from January 2015 to December 2018?
2.
Are there differences between Māori, Pacific people, Asian people, and sole Europeans (by age and gender) in access to H. pylori treatment and type of H. pylori treatment (triple therapy, quadruple therapy) dispensed to New Zealand health server users from January 2015 to December 2018?
For the Northern Region New Zealand population:
3.
Are there differences in the rates of H. pylori tests performed and positive tests between Māori, Pacific people, Asian people, and sole Europeans in Northern New Zealand health server users from January 2015 to December 2018?
4.
Are there inequities in timeliness of subsequent treatment of H. pylori after a positive H. pylori stool antigen from January 2015 to December 2018?
Methods:
A narrative literature review was conducted comparing the recommended practice of H. pylori using sixteen H. pylori guidelines, including national guidelines from New Zealand. This was followed by a quantitative analysis using multiple national health data collections from 2014 to 2018 and that spans four sections (aligning with the research questions above): nationwide stomach cancer and peptic hospitalisation rates, nationwide H. pylori treatment rates, H. pylori testing rates (Northern region only), and time to treatment (Northern region only). Data sources included the health service user population, cancer registry, mortality collection, national minimum dataset, pharmaceutical collection and TestSafe dataset. Data were analysed by ethnicity (total Māori, Pacific and Asian compared to sole European) in all sections and by age group and gender, where possible. Stomach cancer and peptic ulcer disease incidence and mortality rates were age-standardised using the 2001 Māori census populations to allow comparisons between groups and over time.
Results:
H. pylori-associated health outcomes (incidence of stomach cancer and peptic ulcer disease, especially non-cardia stomach cancer) were higher in Māori and Pacific populations than in sole European. Māori (6.6 per 100,000) and Pacific peoples (7.5 per 100,000) were least likely to be tested for H. pylori compared to Asian (21.8 per 100,000) and sole European (12.1 per 100,000). However, there was a higher likelihood that tests were positive in Māori and Pacific people. There was a shift in the test type used as stool tests doubled from 2015-2018. Crude treatment rates were highest in Asian people (5.0 per 1,000), followed by Pacific people (2.0 per 1,000), Māori (1.2 per 1,000), and sole Europeans (1.0 per 1,000). In the Northern region, Asian were more likely to be dispensed treatment quicker in response to infection confirmation compared to sole Europeans, Māori, and Pacific peoples.
Conclusion:
The New Zealand guidelines reflect on the differences in H. pylori and stomach cancer risk between ethnic groups however, the findings of this thesis suggest that the recommendations are not strong enough as there is possible relative undertesting of H. pylori in Māori and Pacific. The dispensing of treatment in Māori and Pacific people is also not reflective of the positivity rate of tests. This may be causing some of the ethnic disparities in stomach cancer and peptic ulcer rates. More research is needed including new H. pylori prevalence estimates to understand if the results in this thesis show true undertesting in Māori and Pacific people. Furthermore, the New Zealand guidelines need to be revised, focusing on producing equitable H. pylori management.