Browsing by Author "Priest P"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Creating symptom-based criteria for diagnostic testing: a case study based on a multivariate analysis of data collected during the first wave of the COVID-19 pandemic in New Zealand
    (BioMed Central Ltd, 2021-12) French N; Jones G; Heuer C; Hope V; Jefferies S; Muellner P; McNeill A; Haslett S; Priest P
    BACKGROUND: Diagnostic testing using PCR is a fundamental component of COVID-19 pandemic control. Criteria for determining who should be tested by PCR vary between countries, and ultimately depend on resource constraints and public health objectives. Decisions are often based on sets of symptoms in individuals presenting to health services, as well as demographic variables, such as age, and travel history. The objective of this study was to determine the sensitivity and specificity of sets of symptoms used for triaging individuals for confirmatory testing, with the aim of optimising public health decision making under different scenarios. METHODS: Data from the first wave of COVID-19 in New Zealand were analysed; comprising 1153 PCR-confirmed and 4750 symptomatic PCR negative individuals. Data were analysed using Multiple Correspondence Analysis (MCA), automated search algorithms, Bayesian Latent Class Analysis, Decision Tree Analysis and Random Forest (RF) machine learning. RESULTS: Clinical criteria used to guide who should be tested by PCR were based on a set of mostly respiratory symptoms: a new or worsening cough, sore throat, shortness of breath, coryza, anosmia, with or without fever. This set has relatively high sensitivity (> 90%) but low specificity (< 10%), using PCR as a quasi-gold standard. In contrast, a group of mostly non-respiratory symptoms, including weakness, muscle pain, joint pain, headache, anosmia and ageusia, explained more variance in the MCA and were associated with higher specificity, at the cost of reduced sensitivity. Using RF models, the incorporation of 15 common symptoms, age, sex and prioritised ethnicity provided algorithms that were both sensitive and specific (> 85% for both) for predicting PCR outcomes. CONCLUSIONS:  If predominantly respiratory symptoms are used for test-triaging,  a large proportion of the individuals being tested may not have COVID-19. This could overwhelm testing capacity and hinder attempts to trace and eliminate infection. Specificity can be increased using alternative rules based on sets of symptoms informed by multivariate analysis and automated search algorithms, albeit at the cost of sensitivity. Both sensitivity and specificity can be improved through machine learning algorithms, incorporating symptom and demographic data, and hence may provide an alternative approach to test-triaging that can be optimised according to prevailing conditions.
  • Thumbnail Image
    Item
    Ethnic equity in Aotearoa New Zealand's COVID-19 response: A descriptive epidemiological study
    (Elsevier Limited, United Kingdom, on behalf of The Royal Society for Public Health, 2025-07) Jefferies S; Gilkison C; Duff P; Grey C; French N; Carr H; Priest P; Crengle S
    Objectives: Aotearoa New Zealand employed one of the most stringent public health pandemic responses internationally. We investigated whether ethnic health equity was achieved in the response and outcomes, from COVID-19 elimination in June 2020 through to Omicron-response easing, including international border reopening, in 2022. Study design: Descriptive epidemiology study. Methods: All COVID-19 cases, patients tested for SARS-CoV-2 and people vaccinated against COVID-19 between 9 June 2020 and 13 April 2022 were examined over three response periods: by demographic features and COVID-19 outcomes, transmission and vaccination patterns, time-to-vaccination and testing rates. Results: There were 15,693 cases per 100,000, 138·7 hospitalisations per 100,000, and 9·8 deaths per 100,000 people. Pacific peoples and Indigenous Māori had, respectively, 9·3 to 35-fold and 1·5 to 8·3-fold higher risk of COVID-19, 5·1-fold and 2·6-fold higher age-standardised risk of hospitalisation and 9-fold and 4-fold higher age-standardised risk of death, than European or Other. Māori and Pacific peoples had lower vaccination coverage at critical points in the response, and slower access to vaccination (Adjusted Time Ratios for two doses 1·32 (95% CI 1·31–1·32) and 1·14 (1·14–1·14), respectively), than European or Other. Testing rates remained high, especially among Māori and Pacific peoples. Conclusions: Despite achieving a low overall burden of disease by international comparisons, the multi-faceted New Zealand response did not prevent stark ethnic inequities in access to vaccination and COVID-19 outcomes. Policies which address disparities in upstream determinants, early vaccine programme planning and implementation with high-risk communities, and prioritisation that addresses systematic ethnic disadvantage and promotes health equity in response decisions is recommended.
  • Thumbnail Image
    Item
    Sensitivity of Reverse Transcription Polymerase Chain Reaction Tests for Severe Acute Respiratory Syndrome Coronavirus 2 Through Time
    (Oxford University Press on behalf of Infectious Diseases Society of America, 2023-01-01) Binny RN; Priest P; French NP; Parry M; Lustig A; Hendy SC; Maclaren OJ; Ridings KM; Steyn N; Vattiato G; Plank MJ
    BACKGROUND: Reverse transcription polymerase chain reaction (RT-PCR) tests are the gold standard for detecting recent infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Reverse transcription PCR sensitivity varies over the course of an individual's infection, related to changes in viral load. Differences in testing methods, and individual-level variables such as age, may also affect sensitivity. METHODS: Using data from New Zealand, we estimate the time-varying sensitivity of SARS-CoV-2 RT-PCR under varying temporal, biological, and demographic factors. RESULTS: Sensitivity peaks 4-5 days postinfection at 92.7% (91.4%-94.0%) and remains over 88% between 5 and 14 days postinfection. After the peak, sensitivity declined more rapidly in vaccinated cases compared with unvaccinated, females compared with males, those aged under 40 compared with over 40s, and Pacific peoples compared with other ethnicities. CONCLUSIONS: Reverse transcription PCR remains a sensitive technique and has been an effective tool in New Zealand's border and postborder measures to control coronavirus disease 2019. Our results inform model parameters and decisions concerning routine testing frequency.
  • Thumbnail Image
    Item
    Zoonotic transmission of asymptomatic carriage Staphylococcus aureus on dairy farms in Canterbury, New Zealand.
    (Microbiology Society, 2024-12-04) Straub C; Taylor W; French NP; Murdoch DR; Priest P; Anderson T; Scott P
    Zoonotic pathogen transmission is of growing concern globally, with agricultural intensification facilitating interactions between humans, livestock and wild animals. Staphylococcus aureus is a major human pathogen, but it also causes mastitis in dairy cattle, leading to an economic burden on the dairy industry. Here, we investigated transmission within and between cattle and humans, including potential zoonotic transmission of S. aureus isolated from cattle and humans from three dairy farms and an associated primary school in New Zealand. Nasal swabs (N=170) were taken from healthy humans. Inguinal and combined nasal/inguinal swabs were taken from healthy cattle (N=1163). Whole-genome sequencing was performed for 96 S. aureus isolates (44 human and 52 cattle). Multilocus sequence typing and assessments of antimicrobial resistance and virulence were carried out. Potential within- and across-species transmission events were determined based on single nucleotide polymorphisms (SNPs). Thirteen potential transmission clusters were detected, with 12 clusters restricted to within-species and one potential zoonotic transmission cluster (ST5). Potential transmission among cattle was mostly limited to single age groups, likely because different age groups are managed separately on farms. While the prevalence of antimicrobial resistance (AMR) was low among both bovine and human isolates, the discovery of an extended-spectrum beta-lactamase gene (bla TEM-116) in a bovine isolate was concerning. This study provides evidence around frequency and patterns of potential transmission of S. aureus on dairy farms and highlights the AMR and virulence profile of asymptomatic carriage S. aureus isolates.