Combined multiplex panel test results are a poor estimate of disease prevalence without adjustment for test error.

Multiplex panel tests identify many individual pathogens at once, using a set of component tests. In some panels the number of components can be large. If the panel is detecting causative pathogens for a single syndrome or disease then we might estimate the burden of that disease by combining the results of the panel, for example determining the prevalence of pneumococcal pneumonia as caused by many individual pneumococcal serotypes. When we are dealing with multiplex test panels with many components, test error in the individual components of a panel, even when present at very low levels, can cause significant overall error. Uncertainty in the sensitivity and specificity of the individual tests, and statistical fluctuations in the numbers of false positives and false negatives, will cause large uncertainty in the combined estimates of disease prevalence. In many cases this can be a source of significant bias. In this paper we develop a mathematical framework to characterise this issue, we determine expressions for the sensitivity and specificity of panel tests. In this we identify a counter-intuitive relationship between panel test sensitivity and disease prevalence that means panel tests become more sensitive as prevalence increases. We present novel statistical methods that adjust for bias and quantify uncertainty in prevalence estimates from panel tests, and use simulations to test these methods. As multiplex testing becomes more commonly used for screening in routine clinical practice, accumulation of test error due to the combination of large numbers of test results needs to be identified and corrected for.

Trends in deprivation in hospitalisations of Indigenous children and young people in Aotearoa New Zealand.

AIM: To examine the 20-year trends in socio-economic inequities in hospitalisations of Maori and non-Maori non-Pacific (NMNP) under-25-year olds in Aotearoa New Zealand. METHODS: Hospital discharge data for Maori and NMNP taitamariki aged under-25 years were extracted from the National Minimum Dataset for the period 2000-2019. Acute or arranged admissions to hospital were included where the primary diagnosis was for a medical condition. Age- and gender-standardised rates (per 1000, 0-24-year old) were calculated for both ethnic groups by area deprivation using the 2013 NZ census estimated resident population. For each ethnic group, inequity indices of socio-economic deprivation (Slope Index of Inequality and Relative Index of Inequality) were computed, using regression modelling, to quantify inequity of medical condition-related hospitalisations and its changes over time. RESULTS: Hospitalisation rates for medical conditions were consistently higher for Maori than for NMNP under-25-year olds from 2000 to 2019. Maori taitamariki residing in the most deprived (quintile 5) areas were more likely than NMNP to be hospitalised for a medical condition at each time point. Deprivation inequities existed for both ethnic groups and were greater for Maori. Despite reducing deprivation inequities over time, ethnic differences persist on both absolute and relative scales. CONCLUSION: Deprivation inequities in hospitalisation for medical conditions persist for Maori taitamariki compared with NMNP and highlights society's tolerance of enduring inequity in health outcomes.

Shoulder dystocia, umbilical cord blood gases and neonatal encephalopathy.

The interpretation of umbilical cord gases may not be straightforward following shoulder dystocia. We reviewed Perinatal and Maternal Mortality Review Committee data from New Zealand infants with moderate and severe neonatal encephalopathy (NE) for 2010-2017 inclusive. If one or more of: pH of ≤7.1; base excess of ≤-12 mmol/L; or lactate of ≥6 mmol/L were present it was considered an abnormal result. One-third (12/36) of infants born following shoulder dystocia had documented umbilical cord gases within the normal range. It is important for clinicians to be aware of this possibility when assessing newborn infants with NE.

Estimating the burden of vaccine preventable lower respiratory tract disease in primary care, UK: protocol for a prospective surveillance study (AvonCAP GP2).

BACKGROUND: The true burden of acute lower respiratory tract diseases (aLRTD; includes acute lower respiratory tract infection, acute exacerbation of pre-existing heart failure and chronic lung disease) among adults presenting to primary care, and the proportion that are potentially vaccine preventable, is unknown. AIMS: To describe aLRTD incidence in adults presenting to primary care; estimate proportions caused by RSV, SARS-CoV-2 and pneumococcus; and investigate disease burden from patient and NHS perspectives. DESIGN & SETTING: Primary care prospective cohort study conducted in six representative General Practices (total Ì´83 000 registered adults) in Bristol, UK. METHOD: Adults (aged≥18 years) registered at participating General Practices and presenting to primary care (in-hours or out-of-hours) or emergency department (if not admitted) with aLRTD will be eligible and identified by real-time primary care record searches. Researchers will screen electronic GP records, including free text, contact patients to assess eligibility, and offer enrolment in a surveillance study and an enhanced diagnostic study (urine, saliva and respiratory samples; physical examination; and symptom diaries). Data will be collected for all aLRTD episodes, with patients assigned to one of three arms: surveillance, embedded diagnostic, and descriptive dataset. Outcome measures will include clinical and pathogen defined aLRTD incidence rates, symptom severity and duration, NHS contacts and costs, health-related quality of life changes, and mortality (≤30 days post identification). CONCLUSION: This comprehensive surveillance study of adults presenting to primary care with aLRTD, with embedded detailed data and sample collection, will provide an accurate assessment of aLRTD burden due to vaccine preventable infections.

State of child health: acute rheumatic fever in Aotearoa New Zealand.

Rheumatic fever is a well-recognised public health problem in Aotearoa New Zealand that is potentially preventable by addressing the social and environmental determinants of health and ensuring equitable access to primary healthcare services. We present data on the hospitalisations of children aged 0-14 years for acute rheumatic fever (ARF) during the period 2000-2020, and the early stages of the COVID-19 pandemic to May 2021. Persistent inequity by ethnicity and by socioeconomic deprivation was observed, particularly for Pacific children, for Maori children, and for children living in the most deprived areas (NZDep quintile 5). The government implemented a programme to prevent rheumatic fever between July 2012 and June 2017. Hospitalisation data suggest that the programme was reducing the incidence of ARF in children, but this trend was not sustained. There was minimal change to the number of hospitalisations for ARF during early period of the COVID-19 pandemic. If untreated, ARF can cause chronic rheumatic heart disease. The persistently high rates of hospitalisations and the unequal burden of disease for vulnerable groups should no longer be tolerated, since they can be effectively addressed by implementation of evidence-based strategies to prevent, treat, and control this disease.

Deprivation trends in potentially avoidable medical hospitalisations of under-25-year-old Maori and non-Maori non-Pacific in Aotearoa New Zealand: a 20-year perspective.

Unnecessary hospitalisations for preventable or treatable conditions provides an indication of the health of a country and its systems. We present data on potentially avoidable hospitalisations of Maori and non-Maori non-Pacific (NMNP) under-25-year-olds for medical conditions during the period 2000-2019, with particular focus on the magnitude of inequity by area deprivation. Potentially avoidable hospitalisation rates of under-25 years for medical conditions were consistently higher for Maori than for NMNP over the 20-year study period. The absolute difference in potentially avoidable hospitalisation rates between the most and least deprived areas were greater for Maori than for NMNP in all years of the study. Respiratory conditions and skin infections accounted for more than 60% of potentially avoidable hospitalisations of Maori under-25-year-olds. The persistent trends in deprivation-based inequities in health outcomes for Maori, on both absolute and relative scales, suggest greater attention needs to be paid to implementing effective policy focussed on reducing these deprivation-based inequities and on improving access to and quality of care.