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 - -
Morriston Hospital 3,004 10 0.3 Singleton Hospital 1,524 - - Neath Port Talbot 804 - - Princess of Wales Hospital 1,441 9 0.6
University Hospital of Wales 2,720 15 0.5 University Hospital Llandough 1,402 - -
Prince Charles Hospital 698 - - The Royal Glamorgan Hospital 1,582 7 0.4
Nevill Hall Hospital 1,426 38 2.6 Royal Gwent Hospital 2,347 32 1.3
All* 23,810 431 1.8
Produced by Public Health Wales Observatory, using CCMDS
*The method of data extraction of the numerator limits each patient aged 16+ to one admission per calendar year and per hospital site - this answers the question "On average, how many people (aged 16+) have had at least one admission to critical care at the hospital site in question?" allowing one admission per year for the 2008-10 period. Only records with a valid LSOA of residence were included in the analysis; 344 patients (1.4%) were excluded due an invalid LSOA code. ** Figures have been suppressed where there were <5 persons admitted 3.4 Dataset quality
Overall the Critical Care Minimum Dataset is of satisfactory quality in terms of data completeness and validity. However, it must be noted that in undertaking this analysis, 822 individual admission records for Welsh residents in 2008-2010 were excluded at the outset due having a missing/invalid NHS ID number. When the person-based analysis was carried out, 3.2% of patients were excluded from the analysis due to
Date: 7 September 2012 Version: 1 Page: 5 of 26
Public Health Wales Observatory Critical care population catchment miscoding or unrecognised coding over the three year period. 1.9% of these excluded patients attended a single unit for treatment which was unknown and represented by a ‘dummy’ code. This particularly affects Gwynedd and Anglesey. 0.4% of the exclusions were made due to patients having an invalid lower super output area (LSOA) of residence while having a valid local authority code of residence (102 patients).
Date: 7 September 2012 Version: 1 Page: 6 of 26
4 Results
4.1 Provider matrix
Persons admitted* to Welsh critical care units, by health board of residence (Wales residents only), persons aged 16+, 2008-2010
Health board of residence Bet si Abertawe Bro Cardiff and Powys Aneurin All Welsh Cadwaladr Hywel Dda Morgannwg Vale Cwm Taf Teaching Bevan residents University University University Critical care unit
Ysbyty Gwynedd 616------616 Ysbyty Glan Clw yd 1,551------1,551 Wrexham Maelor Hospital 1,6406- ----1,646 Betsi Cadwaladr units 3,8076- ----3,813
Bronglais General Hospital 97 136 522 - - - - 755 Withybush General Hospital --968----968 West Wales General Hospital --7498---757 Prince Philip Hospital - - 511 29 - - - 540 Hywel Dda units 97 136 2,75037---3,020
Morriston Hospital 9 88 507 2,273 50 32 45 3,004 Singleton Hospital -37931,384 - - - 1,514 Neath Port Talbot - 12 - 774 10 - - 796 Princess of Wales Hospital --161,274 112 29 6 1,437 ABM units 91376165,705 172 61 51 6,751
University Hospital of Wales 621811171,666 249 580 2,720 University Hospital Llandough -1059571,076 72 127 1,401 Cardiff and Vale units 6 31 140 174 2,742 321 707 4,121
Prince Charles Hospital - 13 - - - 486 196 695 The Royal Glamorgan Hospital -5 -17521,455 51 1,580 Cwm Taf units - 18 - 17 52 1,941 247 2,275
Nevill Hall Hospital - 200 - - - 8 1,211 1,419 Royal Gwent Hospital -10- -1392,308 2,340 Aneurin Bevan units - 210 - - 13 17 3,519 3,759
All units** 3,919 538 3,506 5,933 2,979 2,340 4,524 23,739
Produced by Public Health Wales Observatory, using CCMDS (NWIS) *The method of data extraction limits each patient aged 16+ to one admission per calendar year and per hospital site - this answers the question "On average, how many people resident in Wales (aged 16+) have had at least one admission to critical care at the hospital site in question?" per year on average for the 2008-10 period. **Total for units included in the table "-" denotes less than 5 persons admitted
Public Health Wales Observatory Critical care population catchment
4.2 Summary of catchment populations
Caution for interpretation
• Catchment populations are calculated for the adult population only (ages 16+). • Only Welsh residents are included in catchment populations. • Catchment populations for units near the Wales-England border will have a tendency to be over-estimated where Wales residents attend English critical care units; and under-estimated where English patients attend Welsh units. • MSOAs with small numbers of persons admitted to critical care (less than four) were excluded from the analysis; this applied to seven MSOAs. • A critical care unit with an invalid code accounted for 1.9% of patients, who therefore had to be excluded. This particularly affects Gwynedd and Anglesey. A total of 3.2% of patients had to be excluded due to miscoding or unrecognised coding.
For further details on the limitations of this analysis see section 3.
Date: 7 September 2012 Version: 1 Page: 8 of 26
Public Health Wales Observatory Critical care population catchment
Annual average catchment population, Wales residents aged 16 and over by hospital site for critical care units, 2008-2010
Wales residents Average annual Annual average Hospital catchment population1 persons admitted2
Ysbyty Gw ynedd 135,300 207 Ysbyty Glan Clw yd 190,100 518 Wrexham Maelor Hospital 229,100 549
Bronglais General Hospital 68,400 253 Withybush General Hospital 74,600 326 Glangwili General Hospital 77,600 253 Prince Philip Hospital 48,900 181
Morriston Hospital 220,600 1,001 Singleton Hospital 105,900 508 Neath Port Talbot 47,200 268 Princess of Wales Hospital 122,600 480
University Hospital of Wales 329,500 907 University Hospital Llandough 155,700 467
Prince Charles Hospital 78,600 233 The Royal Glamorgan Hospital 150,700 527
Nevill Hall Hospital 134,200 475 Royal Gwent Hospital 242,600 782
All* 2,411,600 7,937 Produced by Public Health Wales Observatory, using CCMDS (NWIS) & MYE (ONS)
*This is the total of all units included in the table. MSOA populations where less than four persons were admitted to critical care in 2008-10 have been excluded from the analysis.
1 Based on 2008-2010 admission patterns where there were four or more persons admitted to a critical care unit in Wales according to MSOA of residence. Figures are rounded to the nearest 100 and include Wales residents only. 2 The method of data extraction limits each patient aged 16+ to one admission per calendar year and per hospital site - this answers the question "On average, how many people resident in Wales (aged 16+) have had at least one admission to critical care at the hospital site in question?" per year on average for the 2008-10 period.
Date: 7 September 2012 Version: 1 Page: 9 of 26
Public Health Wales Observatory Critical care population catchment
4.3 Catchment maps for critical care units
4.3.1 Ysbyty Gywnedd
Date: 7 September 2012 Version: 1 Page: 10 of 26
Public Health Wales Observatory Critical care population catchment
4.3.2 Ysbyty Glan Clwyd
Date: 7 September 2012 Version: 1 Page: 11 of 26
Public Health Wales Observatory Critical care population catchment
4.3.3 Wrexham Maelor Hospital
Date: 7 September 2012 Version: 1 Page: 12 of 26
Public Health Wales Observatory Critical care population catchment
4.3.4 Bronglais General Hospital
Date: 7 September 2012 Version: 1 Page: 13 of 26
Public Health Wales Observatory Critical care population catchment
4.3.5 Withybush General Hospital
Date: 7 September 2012 Version: 1 Page: 14 of 26
Public Health Wales Observatory Critical care population catchment
4.3.6 Glangwili General Hospital
Date: 7 September 2012 Version: 1 Page: 15 of 26
Public Health Wales Observatory Critical care population catchment
4.3.7 Prince Philip Hospital
Date: 7 September 2012 Version: 1 Page: 16 of 26
Public Health Wales Observatory Critical care population catchment
4.3.8 Morriston Hospital
Date: 7 September 2012 Version: 1 Page: 17 of 26
Public Health Wales Observatory Critical care population catchment
4.3.9 Singleton Hospital
Date: 7 September 2012 Version: 1 Page: 18 of 26
Public Health Wales Observatory Critical care population catchment
4.3.10 Neath Port Talbot Hospital
Date: 7 September 2012 Version: 1 Page: 19 of 26
Public Health Wales Observatory Critical care population catchment
4.3.11 Princess of Wales Hospital
Date: 7 September 2012 Version: 1 Page: 20 of 26
Public Health Wales Observatory Critical care population catchment
4.3.12 University Hospital of Wales
Date: 7 September 2012 Version: 1 Page: 21 of 26
Public Health Wales Observatory Critical care population catchment
4.3.13 University Hospital of Llandough
Date: 7 September 2012 Version: 1 Page: 22 of 26
Public Health Wales Observatory Critical care population catchment
4.3.14 Prince Charles Hospital
Date: 7 September 2012 Version: 1 Page: 23 of 26
Public Health Wales Observatory Critical care population catchment
4.3.15 Royal Glamorgan Hospital
Date: 7 September 2012 Version: 1 Page: 24 of 26
Public Health Wales Observatory Critical care population catchment
4.3.16 Nevill Hall Hospital
Date: 7 September 2012 Version: 1 Page: 25 of 26
Public Health Wales Observatory Critical care population catchment
4.3.17 Royal Gwent Hospital
Date: 7 September 2012 Version: 1 Page: 26 of 26