Lactate, Base Excess, and the Pediatric Index of Mortality: Exploratory Study of an International, Multicenter Dataset.

OBJECTIVES: To investigate the relationship between ICU admission blood lactate, base excess, and ICU mortality and to explore the effect of incorporating blood lactate into the Pediatric Index of Mortality. DESIGN: Retrospective cohort study based on data prospectively collected on every PICU admission submitted to the U.K. Pediatric Intensive Care Audit Network and to the Australia and New Zealand Pediatric Intensive Care Registry. SETTING: Thirty-three PICUs in the United Kingdom/Republic of Ireland and nine PICUs and 20 general ICUs in Australia and New Zealand. PATIENTS: All ICU admissions between January 1, 2012, and December 31, 2015. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: One hundred twenty-three thousand two hundred fifty-two admissions were recorded in both datasets; 81,576 (66.2%) in the United Kingdom/Republic of Ireland and 41,676 (33.8%) in Australia and New Zealand. Of these 75,070 (61%) had a base excess recorded, 63,316 (51%) had a lactate recorded, and 60,876 (49%) had both base excess and lactate recorded. Median lactate value was 1.5 mmol/L (interquartile range, 1-2.4 mmol/L) (United Kingdom/Republic of Ireland: 1.5 [1-2.5]; Australia and New Zealand: 1.4 [1-2.3]). Children with a lactate recorded had a higher illness severity, were more likely to be invasively ventilated, admitted after cardiac surgery, and had a higher mortality rate, compared with admissions with no lactate recorded (p < 0.001). The relationship between lactate and mortality was stronger (odds ratio, 1.32; 95% CI, 1.31-1.34) than between absolute base excess and mortality (odds ratio, 1.13; 95% CI, 1.12-1.14). Addition of lactate to the Pediatric Index of Mortality score led to a small improvement in performance over addition of absolute base excess, whereas adding both lactate and absolute base excess achieved the best performance. CONCLUSIONS: At PICU admission, blood lactate is more strongly associated with ICU mortality than absolute base excess. Adding lactate into the Pediatric Index of Mortality model may result in a small improvement in performance. Any improvement in Pediatric Index of Mortality performance must be balanced against the added burden of data capture when considering potential incorporation into the Pediatric Index of Mortality model.

GPs' role in caring for children and young people with life-limiting conditions: a retrospective cohort study.

BACKGROUND: GPs are rarely actively involved in healthcare provision for children and young people (CYP) with life-limiting conditions (LLCs). This raises problems when these children develop minor illness or require management of other chronic diseases. AIM: To investigate the association between GP attendance patterns and hospital urgent and emergency care use. DESIGN AND SETTING: Retrospective cohort study using a primary care data source (Clinical Practice Research Datalink) in England. The cohort numbered 19 888. METHOD: CYP aged 0-25 years with an LLC were identified using Read codes (primary care) or International Classification of Diseases 10 th Revision (ICD-10) codes (secondary care). Emergency inpatient admissions and accident and emergency (A&E) attendances were separately analysed using multivariable, two-level random intercept negative binomial models with key variables of consistency and regularity of GP attendances. RESULTS: Face-to-face GP surgery consultations reduced, from a mean of 7.12 per person year in 2000 to 4.43 in 2015. Those consulting the GP less regularly had 15% (95% confidence interval [CI] = 10% to 20%) more emergency admissions and 5% more A&E visits (95% CI = 1% to 10%) than those with more regular consultations. CYP who had greater consistency of GP seen had 10% (95% CI = 6% to 14%) fewer A&E attendances but no significant difference in emergency inpatient admissions than those with lower consistency. CONCLUSION: There is an association between GP attendance patterns and use of urgent secondary care for CYP with LLCs, with less regular GP attendance associated with higher urgent secondary healthcare use. This is an important area for further investigation and warrants the attention of policymakers and GPs, as the number of CYP with LLCs living in the community rises.

Ethnic-specific mortality of infants undergoing congenital heart surgery in England and Wales.

PURPOSE: To investigate ethnic differences in mortality for infants with congenital heart defects (CHDs) undergoing cardiac surgery or interventional catheterisation. DESIGN: Observational study of survival to age 1 year using linked records from routine national paediatric cardiac surgery and intensive care audits. Mortality risk was investigated using multivariable Poisson models with multiple imputation. Predictors included sex, ethnicity, preterm birth, deprivation, comorbidities, prenatal diagnosis, age and weight at surgery, preprocedure deterioration and cardiac diagnosis. SETTING: All paediatric cardiac surgery centres in England and Wales. PATIENTS: 5350 infants with CHDs born from 2006 to 2009. MAIN OUTCOME MEASURE: Survival at age 1 year. RESULTS: Mortality was 83.9 (95% CI 76.3 to 92.1) per 1000 infants, with variation by ethnic group. Compared with those of white ethnicity, infants in British Asian (Indian, Pakistani and Bangladeshi) and 'all other' (Chinese, mixed and other) categories experienced significantly higher mortality by age 1 year (relative risk [RR] 1.52[95% CI 1.19 to 1.95]; 1.62[95% CI 1.20 to 2.20], respectively), specifically during index hospital admission (RR 1.55 [95% CI 1.07 to 2.26]; 1.64 [95% CI 1.05 to 2.57], respectively). Further predictors of mortality included non-cardiac comorbidities, prenatal diagnosis, older age at surgery, preprocedure deterioration and cardiac diagnosis. British Asian infants had higher mortality risk during elective hospital readmission (RR 1.86 [95% CI 1.02 to 3.39]). CONCLUSIONS: Infants of British Asian and 'all other' non-white ethnicity experienced higher postoperative mortality risk, which was only partly explained by socioeconomic deprivation and access to care. Further investigation of case-mix and timing of risk may provide important insights into potential mechanisms underlying ethnic disparities.

Comparison of ethnic group classification using naming analysis and routinely collected data: application to cancer incidence trends in children and young people.

OBJECTIVE: Inpatient Hospital Episode Statistics (HES) ethnicity data are available but not always collected and data quality can be unreliable. This may have implications when assessing outcomes by ethnicity. An alternative method for assigning ethnicity is using naming algorithms. We investigate if the association between ethnicity and cancer incidence varied dependent on how ethnic group was assigned. DESIGN: Population-based cancer registry cohort study. SETTING: Yorkshire, UK. PARTICIPANTS: Cancer registrations from 1998 to 2009 in children and young people (0-29 years) from a specialist cancer register in Yorkshire, UK (n=3998) were linked to inpatient HES data to obtain recorded ethnicity. Patients' names, recorded in the cancer register, were matched to an ethnic group using the naming algorithm software Onomap. Each source of ethnicity was categorised as white, South Asian (SA) or Other, and a further two indicators were defined based on the combined ethnicities of HES and Onomap, one prioritising HES results, the other prioritising Onomap. OUTCOMES: Incidence rate ratios (IRR) between ethnic groups were compared using Poisson regression for all cancers combined, leukaemia, lymphoma and central nervous system (CNS) tumours. RESULTS: Depending on the indicator used, 7.1%-8.6% of the study population were classified as SA. For all cancers combined there were no statistically significant differences between white and SA groups using any indicator; however, for lymphomas significant differences were only evident using one of the 'Combined' indicators (IRR=1.36 (95% CI 1.08 to 1.71)), and for CNS tumours incidence was lower using three of the four indicators. For the other ethnic group the IRR for all cancers combined ranged from 0.78 (0.65 to 0.94) to 1.41 (1.23 to 1.62). CONCLUSIONS: Using different methods of assigning ethnicity can result in different estimates of ethnic variation in cancer incidence. Combining ethnicity from multiple sources results in a more complete estimate of ethnicity than the use of one single source.

Outcomes for Children Receiving Noninvasive Ventilation as the First-Line Mode of Mechanical Ventilation at Intensive Care Admission: A Propensity Score-Matched Cohort Study.

OBJECTIVES: To compare outcomes of children receiving noninvasive ventilation with those receiving invasive ventilation as first-line mode of mechanical ventilation following unplanned intensive care admission. DESIGN: Propensity score-matched cohort study analyzing data prospectively collected by the Pediatric Intensive Care Audit Network over 8 years (2007-2014). SETTING: Thirty-one PICUs in the United Kingdom and Ireland; twenty-one of whom submitted Pediatric Critical Care Minimum Dataset data for the entire study period. PATIENTS: Children consecutively admitted to study PICUs. Planned admissions following surgery, unplanned admissions from other hospitals, those on chronic ventilation, and those who did not receive mechanical ventilation on the day of PICU admission were excluded. INTERVENTIONS: Use of noninvasive ventilation, rather than invasive ventilation, as the first-line mode of mechanical ventilation. MEASUREMENTS AND MAIN RESULTS: PICU mortality, length of ventilation, length of PICU stay, and ventilator-free days at day 28. During the study period, there were 151,128 PICU admissions. A total of 15,144 admissions (10%) were eligible for analysis once predefined exclusion criteria were applied: 4,804 (31.7%) received "noninvasive ventilation first," whereas 10,221 (67.5%) received "invasive ventilation first"; 119 (0.8%) admissions could not be classified. Admitting PICU site explained 6.5% of the variation in first-line mechanical ventilation group (95% CI, 2.0-19.0%). In propensity score-matched analyses, receiving noninvasive ventilation first was associated with a significant reduction in mortality by 3.1% (95% CI, 1.7-4.6%), length of ventilation by 1.6 days (95% CI, 1.0-2.3), and length of PICU stay by 2.1 days (95% CI, 1.3-3.0), as well as an increase in ventilator-free days at day 28 by 3.7 days (95% CI, 3.1-4.3). CONCLUSIONS: Use of noninvasive ventilation as first-line mode of mechanical ventilation in critically ill children admitted to PICU in an unplanned fashion may be associated with significant clinical benefits. Further high-quality evidence regarding optimal patient selection and timing of initiation of noninvasive ventilation could lead to less variability in clinical care between institutions and improved patient outcomes.

How many children and young people with life-limiting conditions are clinically unstable? A national data linkage study.

OBJECTIVE: To determine the clinical stage (stable, unstable, deteriorating or dying) for children and young people (CYP) aged 0-25 years in Scotland with life-limiting conditions (LLCs). DESIGN: National cohort of CYP with LLCs using linked routinely collected healthcare data. SETTING: Scotland. PATIENTS: 20 436 CYP identified as having LLCs and resident in Scotland between 1 April 2009 and 31 March 2014. MAIN OUTCOME: Clinical stage based on emergency inpatient and intensive care unit admissions and date of death. RESULTS: Over 2200 CYP with LLCs in Scotland were unstable, deteriorating or dying in each year. Compared with 1-year-olds to 5-year-olds, children under 1 year of age had the highest risk of instability (OR 6.4, 95% CI 5.7 to 7.1); all older age groups had lower risk. Girls were more likely to be unstable than boys (OR 1.15, 95% CI 1.06 to 1.24). CYP of South Asian (OR 1.61, 95% CI 1.28 to 2.01), Black (OR 1.58, 95% CI 1.04 to 2.41) and Other (OR 1.33, 95% CI 1.02 to 1.74) ethnicity were more likely to experience instability than White CYP. Deprivation was not a significant predictor of instability. Compared with congenital abnormalities, CYP with most other primary diagnoses had a higher risk of instability; only CYP with a primary perinatal diagnosis had significantly lower risk (OR 0.23, 95% CI 0.19 to 0.29). CONCLUSIONS: The large number of CYP with LLCs who are unstable, deteriorating or dying may benefit from input from specialist paediatric palliative care. The age group under 1 and CYP of South Asian, Black and Other ethnicities should be priority groups.

Death and Emergency Readmission of Infants Discharged After Interventions for Congenital Heart Disease: A National Study of 7643 Infants to Inform Service Improvement.

BACKGROUND: Improvements in hospital-based care have reduced early mortality in congenital heart disease. Later adverse outcomes may be reducible by focusing on care at or after discharge. We aimed to identify risk factors for such events within 1 year of discharge after intervention in infancy and, separately, to identify subgroups that might benefit from different forms of intervention. METHODS AND RESULTS: Cardiac procedures performed in infants between 2005 and 2010 in England and Wales from the UK National Congenital Heart Disease Audit were linked to intensive care records. Among 7976 infants, 333 (4.2%) died before discharge. Of 7643 infants discharged alive, 246 (3.2%) died outside the hospital or after an unplanned readmission to intensive care (risk factors were age, weight-for-age, cardiac procedure, cardiac diagnosis, congenital anomaly, preprocedural clinical deterioration, prematurity, ethnicity, and duration of initial admission; c-statistic 0.78 [0.75-0.82]). Of the 7643, 514 (6.7%) died outside the hospital or had an unplanned intensive care readmission (same risk factors but with neurodevelopmental condition and acquired cardiac diagnosis and without preprocedural deterioration; c-statistic 0.78 [0.75-0.80]). Classification and regression tree analysis were used to identify 6 subgroups stratified by the level (3-24%) and nature of risk for death outside the hospital or unplanned intensive care readmission based on neurodevelopmental condition, cardiac diagnosis, congenital anomaly, and duration of initial admission. An additional 115 patients died after planned intensive care admission (typically following elective surgery). CONCLUSIONS: Adverse outcomes in the year after discharge are of similar magnitude to in-hospital mortality, warrant service improvements, and are not confined to diagnostic groups currently targeted with enhanced monitoring.

Admission to hospital for bronchiolitis in England: trends over five decades, geographical variation and association with perinatal characteristics and subsequent asthma.

BACKGROUND: Admission of infants to hospital with bronchiolitis consumes considerable healthcare resources each winter. We report an analysis of hospital admissions in England over five decades. METHODS: Data were analysed from the Hospital In-Patient Enquiry (HIPE, 1968-1985), Hospital Episode Statistics (HES, 1989-2011), Oxford Record Linkage Study (ORLS, 1963-2011) and Paediatric Intensive Care Audit Network (PICANet, 2003-2012). Cases were identified using International Classification of Diseases (ICD) codes in discharge records. Bronchiolitis was given a separate code in ICD9 (used in England from 1979). Geographical variation was analysed using Local Authority area boundaries. Maternal and perinatal risk factors associated with bronchiolitis and subsequent admissions for asthma were analysed using record-linkage. RESULTS: All-England HIPE and HES data recorded 468 138 episodes of admission for bronchiolitis in infants aged <1 year between 1979 and 2011. In 2011 the estimated annual hospital admission rate was 46.1 (95% CI 45.6 to 46.6) per 1000 infants aged <1 year. Between 2004 and 2011 the rates rose by an average of 1.8% per year in the all-England HES data, whereas admission rates to paediatric intensive care changed little (1.3 to 1.6 per 1000 infants aged <1 year). A fivefold geographical variation in hospital admission rates was observed. Young maternal age, low social class, low birth weight and maternal smoking were among factors associated with an increased risk of hospital admission with bronchiolitis. CONCLUSIONS: Hospital admissions for infants with bronchiolitis have increased substantially in recent years. However, cases requiring intensive care have changed little since 2004.

Population mixing for leukaemia, lymphoma and CNS tumours in teenagers and young adults in England, 1996-2005.

BACKGROUND: Little aetiological epidemiological research has been undertaken for major cancers occurring in teenagers and young adults (TYA). Population mixing, as a possible proxy for infectious exposure, has been well researched for childhood malignancies. We aimed to investigate effects of population mixing in this older age group using an English national cancer dataset. METHODS: Cases of leukaemia, lymphoma and central nervous system (CNS) tumours amongst 15-24 year olds in England (diagnosed 1996-2005) were included in the study. Data were obtained by ward of diagnosis and linked to 1991 census variables including population mixing (Shannon index); data on person-weighted population density and deprivation (Townsend score) were also used and considered as explanatory variables. Associations between TYA cancer incidence and census variables were investigated using negative binomial regression, and results presented as incidence rate ratios (IRR) with 95% confidence intervals (CI). RESULTS: A total of 6251 cases of leukaemia (21%), lymphoma (49%) and CNS tumours (30%) were analysed. Higher levels of population mixing were associated with a significant decrease in the incidence of CNS tumours (IRR=0.83, 95% CI=0.75-0.91), accounted for by astrocytomas and 'other CNS tumours'; however, there was no association with leukaemia or lymphoma. Incidence of CNS tumours and lymphoma was 3% lower in more deprived areas (IRR=0.97, 95% CI=0.96-0.99 and IRR=0.97, 95% CI=.96-0.98 respectively). Population density was not associated with the incidence of leukaemia, lymphoma or CNS tumours. CONCLUSIONS: Our results suggest a possible role for environmental risk factors with population correlates in the aetiology of CNS tumours amongst TYAs. Unlike studies of childhood cancer, associations between population mixing and the incidence of leukaemia and lymphoma were not observed.

Patterns of diagnoses among children and young adults with life-limiting conditions: A secondary analysis of a national dataset.

BACKGROUND: Numbers of children and young people with life-limiting conditions are rising, and increasing lifespans require young adults with life-limiting condition to transit to appropriate adult services. AIM: To describe the prevalence of life-limiting condition in children and young adults by age, sex, diagnostic group, ethnicity and deprivation. DESIGN: A secondary analysis of the English Hospital Episode Statistics dataset was undertaken to calculate prevalence per 10,000 population. SETTING/PARTICIPANTS: Individuals (0-40 years) with life-limiting conditions were identified within an English Hospital Episode Statistics dataset by applying a customised coding framework of International Classification of Diseases, 10th Edition, disease codes. RESULTS: There were 462,962 inpatient hospital admissions for 92,129 individual patients with a life-limiting condition. Prevalence-by-age group curve is U shaped with the highest overall prevalence in the under 1-year age group (127.3 per 10,000), decreasing until age 21-25 years (21.1 per 10,000) before rising steeply to reach 55.5 per 10,000 in the 36-40 -year age group. The distribution by diagnostic group varies by age: congenital anomalies are most prevalent in children until age 16-20 years with oncology diagnoses then becoming the most prevalent. CONCLUSION: Non-malignant diagnoses are common in children and young adults, and services that have historically focussed on oncological care will need to widen their remit to serve this population of life-limited patients. The diagnosis determining a patient's life-limiting condition will strongly influence their palliative care service needs. Therefore, understanding the diagnostic and demographic breakdown of this population of teenagers and young adults is crucial for planning future service provision.

Is fluoride a risk factor for bone cancer? Small area analysis of osteosarcoma and Ewing sarcoma diagnosed among 0-49-year-olds in Great Britain, 1980-2005.

BACKGROUND: Artificial fluoridation of drinking water to improve dental health has long been a topic of controversy. Opponents of this public health measure have cited the possibility of bone cancer induction. The study objective was to examine whether increased risk of primary bone cancer was associated with living in areas with higher concentrations of fluoride in drinking water. METHODS: Case data on osteosarcoma and Ewing sarcoma, diagnosed at ages 0-49 years in Great Britain (GB) (defined here as England, Scotland and Wales) during the period 1980-2005, were obtained from population-based cancer registries. Data on fluoride levels in drinking water in England and Wales were accessed through regional water companies and the Drinking Water Inspectorate. Scottish Water provided data for Scotland. Negative binomial regression was used to examine the relationship between incidence rates and level of fluoride in drinking water at small area level. RESULTS: The study analysed 2566 osteosarcoma and 1650 Ewing sarcoma cases. There was no evidence of an association between osteosarcoma risk and fluoride in drinking water [relative risk (RR) per one part per million increase in the level of fluoride = 1·001; 90% confidence interval (CI) 0·871, 1·151] and similarly there was no association for Ewing sarcoma (RR = 0·929; 90% CI 0·773, 1·115). CONCLUSIONS: The findings from this study provide no evidence that higher levels of fluoride (whether natural or artificial) in drinking water in GB lead to greater risk of either osteosarcoma or Ewing sarcoma.

Small-area analyses of bone cancer diagnosed in Great Britain provide clues to aetiology.

BACKGROUND: The aetiology of bone cancers is poorly understood. This study examined geographical patterning in incidence of primary bone cancers diagnosed in 0-49 year olds in Great Britain during 1980-2005 to provide information on factors linked with disease development. We investigated putative associations with deprivation and population density. METHODS: Data on osteosarcoma and Ewing sarcoma were obtained from national population-based registries. Negative binomial regression was used to examine the relationship between incidence rates and the Townsend deprivation score (and its component variables) and small-area population density. RESULTS: The study analyzed 2566 osteosarcoma and 1650 Ewing sarcoma cases. For females with osteosarcoma, statistically significant decreased risk was associated with higher levels of deprivation (relative risk [RR] per unit increase in deprivation score = 0.969; 95% confidence interval [CI] 0.946-0.993). For all Ewing sarcoma combined, statistically significant decreased risk was associated with greater area-level population density and higher levels of non-car ownership (RR per person per hectare increase = 0.984; 95% CI 0.976-0.993, RR per 1% increase in non-car ownership = 0.994; 95% CI 0.991-0.998). CONCLUSIONS: Higher incidence of osteosarcoma was observed for females in areas with lower deprivation levels indicating increased risk is linked to some aspect of affluent living. Higher incidence of Ewing sarcoma occurred in areas of low population density and where more people owned cars, both characteristic of rural environments. The study adds substantially to evidence associating Ewing sarcoma risk with rural environmental exposures. Putative risk factors include agricultural exposures, such as pesticides and zoonotic agents.

Rising national prevalence of life-limiting conditions in children in England.

BACKGROUND: Life-limiting conditions (LLCs) describe diseases with no reasonable hope of cure that will ultimately be fatal. For children with these diseases, palliative care services should be available but few data are available to estimate the burden of these conditions. METHODS: Children (0-19 years) with LLCs were identified within an English Hospital Episode Statistics dataset (2000/2001-2009/2010) by applying a customized coding framework of the International Classification of Diseases, 10th Revision, disease codes. Prevalence per 10 000 population (0-19 years) was calculated by age, diagnostic group, ethnicity, deprivation, and region for each year. RESULTS: The Hospital Episode Statistics extract contained 175 286 individuals with 1 or more LLCs of which congenital anomalies were the most common (31%). Prevalence increased over 10 years from 25 to 32 per 10 000 population. Prevalence in the South Asian (48 per 10 000); black (42 per 10 000); and Chinese, mixed, and "other" (31 per 10 000) populations were statistically significantly higher compared with the white population (27 per 10 000). Prevalence shows an inverse J-shaped relationship with 5 categories of deprivation, with the highest prevalence in the most deprived areas and the lowest in the second least deprived. CONCLUSIONS: In 2010, the prevalence of LLCs in children in England was double the previously reported estimates and had increased annually in all areas over the past decade. This clearly identifies an escalating need for specialist pediatric palliative care services. When planning services for these increasing needs, the excess prevalence in ethnic minority groups, especially in deprived areas, needs to be considered.

Interbirth interval is associated with childhood type 1 diabetes risk.

Short interbirth interval has been associated with maternal complications and childhood autism and leukemia, possibly due to deficiencies in maternal micronutrients at conception or increased exposure to sibling infections. A possible association between interbirth interval and subsequent risk of childhood type 1 diabetes has not been investigated. A secondary analysis of 14 published observational studies of perinatal risk factors for type 1 diabetes was conducted. Risk estimates of diabetes by category of interbirth interval were calculated for each study. Random effects models were used to calculate pooled odds ratios (ORs) and investigate heterogeneity between studies. Overall, 2,787 children with type 1 diabetes were included. There was a reduction in the risk of childhood type 1 diabetes in children born to mothers after interbirth intervals <3 years compared with longer interbirth intervals (OR 0.82 [95% CI 0.72-0.93]). Adjustments for various potential confounders little altered this estimate. In conclusion, there was evidence of a 20% reduction in the risk of childhood diabetes in children born to mothers after interbirth intervals <3 years.

A cohort study of children and young people with progressive neuromuscular disorders: clinical and demographic profiles and changing patterns of referral for palliative care.

BACKGROUND: Progressive neuromuscular disease in children is life limiting and these children and young people would benefit from palliative care services, but data are limited on the number and demography of these children. AIM: To describe the clinical and demographic profile of children referred to a Children's hospice in the UK with progressive neuromuscular disease. SETTING/PARTICIPANTS: All children and young people with progressive neuromuscular disorders referred to Martin House Children's Hospice between 1987 and 2010. DESIGN: Retrospective cohort study. RESULTS: 300 children with progressive neuromuscular disease were referred to the hospice. Seventy percent (210) of these children had Duchenne Muscular Dystrophy, 22% (67) had Spinal Muscular Atrophy (34 with Type I) and 8% had other neuromuscular diseases. Numbers of referrals have not significantly increased over the last 15 years, although an increasing number come from a South Asian background (from 4% to 32%) and a higher number of children have conditions other than Duchenne Muscular Dystrophy. A total of 55.3% (166) of all referrals came from areas of the highest deprivation. Survival patterns varied by diagnostic group, but ethnicity and deprivation were not associated with survival in these children. CONCLUSIONS: The profile of children with progressive neuromuscular conditions who were referred for palliative care has changed over the last 20 years, with a different spectrum of underlying diagnoses and a greater number from a South Asian background. The higher than expected proportion of children living in areas of high deprivation has been consistent over time.

Referral to a specialist paediatric palliative care service in oncology patients.

Cancer is the second most common cause of death in children and young people (0-19 years) accounting for 16.2% of deaths in England and Wales in 2005. Only 37.6% children and young people who died from cancer in Yorkshire were referred to Martin House Children's Hospice (MH) during the period 1990-2005. A significantly higher proportion with central nervous system tumours and a significantly lower than expected proportion with leukaemia or lymphoma were referred for palliative care. There is potential to increase the proportion of children and young people with cancer who are referred to specialist palliative care services.

Severe head injury in children: intensive care unit activity and mortality in England and Wales.

OBJECTIVE: To explore the relationship between volume of paediatric intensive care unit (PICU) head injury (HI) admissions, specialist paediatric neurosurgical PICU practice, and mortality in England and Wales. METHODS: Analysis of HI cases (age  <16 years) from the Paediatric Intensive Care Audit Network national cohort of sequential PICU admissions in 27 units in England and Wales, in the 5 years 2004-2008. Risk-adjusted mortality using the Paediatric Index of Mortality (PIM) model was compared between PICUs aggregated into quartile groups, first to fourth based on descending number of HI admissions/year: highest volume, medium-higher volume, medium-lower volume, and lowest volume. The effect of category of PICU interventions - observation only, mechanical ventilation (MV) only, and intracranial pressure (ICP) monitoring - on outcome was also examined. Observations were reported in relation to specialist paediatric neurosurgical PICU practice. RESULTS: There were 2575 admissions following acute HI (4.4% of non-cardiac surgery PICU admissions in England and Wales). PICU mortality was 9.3%. Units in the fourth-quartile (lowest volume) group did not have significant specialist paediatric neurosurgical activity on the PICU; the other groups did. Overall, there was no effect of HI admissions by individual PICU on risk-adjusted mortality. However, there were significant effects for both intensive care intervention category (p<0.001) and HI admissions by grouping (p<0.005). Funnel plots and control charts using the PIM model showed a hierarchy in increasing performance from lowest volume (group IV), to medium-higher volume (group II), to highest volume (group I), to medium-lower volume (group III) sectors of the health care system. CONCLUSIONS: The health care system in England and Wales for critically ill HI children requiring PICU admission performs as expected in relation to the PIM model. However, the lowest-volume sector, comprising 14 PICUs with little or no paediatric neurosurgical activity on the unit, exhibits worse than expected outcome, particularly in those undergoing ICP monitoring. The best outcomes are seen in units in the mid-volume sector. These data do not support the hypothesis that there is a simple relationship between PICU volume and performance.

Place of death and palliative care following discharge from paediatric intensive care units.

OBJECTIVE: To determine where children die following discharge from paediatric intensive care units (PICUs) in Great Britain and to investigate if this varies by discharge to palliative care. DESIGN: National cohort of PICU admissions linked to Office of National Statistics death certificate data. SETTING: 31 PICUs in Great Britain. PARTICIPANTS: A cohort of 35 383 children admitted to PICUs between 1 November 2002 until 25 January 2007. MAIN OUTCOME MEASURES: Place of death by palliative care discharge status. RESULTS: 2346 (6.6%) deaths occurred after discharge during the study period, which is more than 10 times the normal child population mortality of 6.0 per 1000. Discharge to palliative care resulted in fewer deaths in hospital (44.1%) (compared to non-palliative care discharges (77.7%)), a greater proportion of deaths were at home (33.3% compared to non-palliative discharges 16.1%) and in a hospice (22.5% compared to non-palliative discharges 5.8%). CONCLUSIONS: Children referred to palliative care services at discharge from PICU are more likely to die in the community (home or hospice) than children not referred to palliative care.

Palliative care discharge from paediatric intensive care units in Great Britain.

We aim to describe the demographics and clinical characteristics of children discharged to palliative care from 31 paediatric intensive care units in Great Britain, using a cohort of admissions and discharges from the database of paediatric intensive care units (Paediatric Intensive Care Audit Network (PICANet)). The patients included in this study were children discharged alive from paediatric intensive care units (n = 68882) between 1 January 2004 and 31 December 2008. The main outcome measure was Odds Ratios for discharge of children from paediatric intensive care units to palliative care and their referral destination. We found that palliative care status was recorded for 68,090 live discharges from paediatric intensive care units, with 492 (0.7%) discharges to palliative care, a proportion that varied by Strategic Health Authority (range 0 to 1.1). The odds of discharge to palliative care were increased by expected probability of death (log odds of mortality) associated with an oncology, neurology or respiratory diagnosis. South Asian children referred to palliative care were less likely to receive this care in a hospice (OR 0.18, 95% CI 0.04,0.83) and more likely to receive it in a hospital setting (OR 2.57, 95% CI 1.16,5.71). We conclude that children admitted to paediatric intensive care units have a very low rate of discharge to palliative care. Specific demographic and clinical variables are associated with referral to palliative care.

What do epidemiologists mean by 'population mixing'?

There is growing evidence that some chronic diseases are caused, or promoted, by infectious disease. 'Population mixing' has been used as a proxy for the range and dose of infectious agents circulating in a community. Given the speculation over the role of population mixing in many chronic diseases, we review the various methods used for measuring population mixing, and provide a classification of these. We recommend that authors fulfill two criteria in publications: measures are demonstrably associated with the putative risk factors for which population-mixing is acting as a proxy and fundamental characteristics of the chosen measures are clearly defined.