Critical Care Population Catchment Maps for Wales Units
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Critical care population catchment maps for Wales units Author: Bethan Patterson (Observatory Analysis Team); Hugo Cosh (Observatory Analysis Team) Date: 7 September 2012 Version: 1 Publication/ Distribution: • Critical care network board Purpose and Summary of Document: To provide a series of catchment maps to indicate the proportion of the adult population of each middle super output area (MSOA) potentially served by each of the critical care units in Wales, and to estimate the adult catchment population for each unit. To outline the methodology used to create the maps and to give consideration to the limitations of their use. The analysis included in this document is based on the Critical Care Minimum Dataset (CCMDS). Due to certain methodological issues, in particular the lack of data from English providers, this should be taken with some caution. Date: 3 July 2012 Version:1 Page: 1 of 26 Public Health Wales Observatory Critical care population catchment CONTENTS 1 INTRODUCTION .......................................................................... 3 2 METHOD ..................................................................................... 3 3 LIMITATIONS ............................................................................. 4 3.1 Geography ..............................................................................4 3.2 Welsh residents attending non-Welsh units ..................................4 3.3 Non-Welsh residents attending Welsh units ..................................5 3.4 Dataset quality.........................................................................5 4 RESULTS ..................................................................................... 7 4.1 Provider matrix ........................................................................7 4.2 Summary of catchment populations ............................................8 4.3 Catchment maps for critical care units....................................... 10 4.3.1 Ysbyty Gywnedd .............................................................. 10 4.3.2 Ysbyty Glan Clwyd ........................................................... 11 4.3.3 Wrexham Maelor Hospital ................................................. 12 4.3.4 Bronglais General Hospital ................................................ 13 4.3.5 Withybush General Hospital............................................... 14 4.3.6 Glangwili General Hospital................................................. 15 4.3.7 Prince Philip Hospital ........................................................ 16 4.3.8 Morriston Hospital............................................................ 17 4.3.9 Singleton Hospital............................................................ 18 4.3.10 Neath Port Talbot Hospital................................................. 19 4.3.11 Princess of Wales Hospital................................................. 20 4.3.12 University Hospital of Wales .............................................. 21 4.3.13 University Hospital of Llandough ........................................ 22 4.3.14 Prince Charles Hospital ..................................................... 23 4.3.15 Royal Glamorgan Hospital ................................................. 24 4.3.16 Nevill Hall Hospital ........................................................... 25 4.3.17 Royal Gwent Hospital ....................................................... 26 Date: 7 September 2012 Version: 1 Page: 2 of 26 Public Health Wales Observatory Critical care population catchment 1 Introduction The South Wales Critical Care Network Board requested a series of population catchment maps to be produced; one for each critical care unit in Wales to indicate the proportion of the adult population in each middle super output area (MSOA) that the critical care units are potentially serving. 2 Method The Critical Care Minimum Dataset (CCMDS) was introduced across Wales in 2007. Data is considered to be complete from 2008 onwards. Therefore, for this analysis, data was extracted from the CCMDS for the calendar years 2008-2010 and includes records for all persons admitted to critical care units in Wales aged 16+. Catchment populations for each critical care unit were calculated by applying the proportion of persons admitted from each MSOA to the unit in question, to the general adult population of that MSOA. The totals from each MSOA were then added together to provide an overall estimation of the adult population catchment for residents in Wales. The method therefore attempts to answer the question: ‘If the total adult population at risk attended the critical care unit in the same proportions as real-life patients did during the selected time period, how many people could each critical care unit potentially be serving?’. This is calculated as: + +… The analysis is person-based as opposed to admissions-based i.e. the numerator was obtained by counting the number of unique persons admitted to critical care units in Wales, allowing one admission per person, per unit, per year for the period 2008-2010, by MSOA of residence. The analysis excludes admissions where the MSOA of residence was outside Wales, where the critical care unit attended was outside Wales, or where records did not provide a valid NHS ID number or critical care unit code. The analysis also excludes data for MSOAs where the number of persons admitted to critical care was three or less in the period 2008-2010; this applied to seven MSOAs. These exclusions have been made reduce the effect that unusual admission patterns may have on the overall catchment population totals i.e. MSOAs near the England-Wales border where almost all patients would be admitted to critical care units in England. Date: 7 September 2012 Version: 1 Page: 3 of 26 Public Health Wales Observatory Critical care population catchment 3 Limitations It is also important to note that the results in this document are estimates only, produced quite crudely by assuming that the entire population aged 16+ of an MSOA would attend Welsh critical care units in the same proportion as patients attending Welsh critical care units in 2008-2010, and are intended only as a rough indication of the Welsh adult population catchment of critical care units in Wales. Some specific limitations are outlined in the sections below. 3.1 Geography The analysis was based on middle super output area (MSOA). MSOAs are geographical area boundaries that have been created by the Office for National Statistics for statistical analyses for small areas. There are 413 MSOAs in Wales and the average population resident per MSOA is around 7,200. Due to the analysis being carried out at this low level geography, there were often small numbers of persons attending critical care units in Wales which could have had an unusual effect on the catchment population totals where admission patterns were untypical. Where there were less than four admissions to critical care units in Wales from a particular MSOA, the population data for those MSOAs were excluded from the calculations; this applied to seven MSOAs. Notably, for the period 2008-2010, two MSOAs did not have any admissions to Welsh critical care units according to the CCMDS. Both of the MSOAs (W02000101 and W02000098) are found on the England-Wales border. Therefore, due to their proximity to English critical care units, it is likely that residents who required critical care, if any, were admitted to units across the border in England. 3.2 Welsh residents attending non-Welsh units As mentioned previously, Welsh residents admitted to critical care units outside of Wales were not included in the calculations. This will have the greatest effect on the MSOAs towards the England-Wales border. For example, if four persons were admitted to critical care in one year, three of which attended an English unit while one attended a Welsh unit, it would appear as though 100% of that MSOA’s patients were admitted to the single Welsh unit as the data for the patients who attended English units will be missing from the calculations. This would result in 100% of the population of that MSOA being included in the catchment population total and lead to an inflated overall estimate for the unit in question. This will only occur in a small number of cases for MSOAs close to the border where four or more persons were admitted to Welsh units, as small numbers have been excluded. Date: 7 September 2012 Version: 1 Page: 4 of 26 Public Health Wales Observatory Critical care population catchment 3.3 Non-Welsh residents attending Welsh units In this analysis, records were excluded where the area of residence was outside Wales. This will result in the catchment population estimates of some critical care units in Wales being under-estimated, especially where units are located close to the England-Wales border and regularly admit Non-Welsh patients. The following table helps to illustrate this by showing the proportion of non-Welsh residents attending critical care units in Wales. This appears to particularly affect Wrexham Maelor Hospital and Ysbyty Glan Clwyd. Patients admitted* to Welsh critical care units who live outside Wales, aged 16 and over by critical care unit, 2008-2010 Welsh residents Non-Welsh residents % Non-Welsh Critical care unit admitted admitted** residents** Ysbyty Gwynedd 620 19 3.0 Ysbyty Glan Clw yd 1,555 77 4.7 Wrexham Maelor Hospital 1,648 178 9.7 Bronglais General Hospital 758 22 2.8 Withybush General Hospital 979 24 2.4 Glangwili General Hospital 760 - - Prince Philip Hospital 542