Scottish Inpatient Patient Experience Survey 2012 Volume 2: Technical Report

4 Sample

Introduction

4.1 This section of the report presents detail on the design of the inpatient survey sample, the sampling frame used by NHS Boards, sample selection, procedures and checks undertaken.

4.2 It also provides detail on the procedures for data transfer of the agreed sample and arrangements around access to data.

Design of sample

4.3 The sampling approach for the Better Together Inpatient Survey was designed to meet the needs of each NHS Board and to inform local improvement work as well as to meaningfully compare findings across Boards and provide national level results.

4.4 In order to meet these requirements, a stratified sampling strategy was developed through consultation between Analytical Services Division (ASD) within the Scottish Government and each NHS Board.

4.5 Sample strata were based on site level (or in the case of some Boards sub-site level). Table 2 provides detail on the number of eligible patients within each NHS Board.

Sampling frame

4.6 NHS Boards were responsible for compiling a list of eligible patients from their records in order to finalise the sample for the survey. The survey guidance manual provided advice on doing this along with inclusion and exclusion criteria.

4.7 Eligible patients were adults (aged 16 years old and above on discharge from hospital) who had an overnight stay in hospital as an inpatient (defined as one night or more where the individual was in hospital at midnight in an inpatient bed) between October 2010 and September 2011.

4.8 Certain patients were excluded from the survey, as follows:

• Privately funded patients receiving care in NHS or private hospitals;
• Scottish NHS patients treated in hospitals outside of Scotland but whose care was commissioned by an NHS Board;
• Patients who were not resident in Scotland;
• Patients who were receiving care as an outpatient or day case which did not result in an overnight stay;
• Patients who were expected to have an overnight stay at admission but did not;
• Patients who stayed in hospital for termination of pregnancy;
• Patients who stayed in a hospital maternity unit;
• Patients who were known to be deceased;
• Patients shown on hospital / ISD systems as being unable to give consent e.g. having incapacity as set out in the Adults with Incapacity (Scotland) Act 2000;
• Inpatients who were being treated for a mental health condition in a mental illness hospital;
• Inpatients who were resident in a long-stay hospital;
• Inpatients who were being treated in a learning disabilities unit; and
• Inpatients aged 15 or less on discharge.

4.9 Based on the selection and exclusion criteria, the total number of inpatients who were eligible to take part in the study was 363,600^[4]. Table 2 summarises the total number of eligible inpatients within each NHS Board.

Table 2 Total number of eligible patients within each NHS Board including deceased patients

NHS Board	Inpatient Population
NHS Ayrshire and Arran	41,814
NHS Borders	6,032
NHS Dumfries and Galloway	6,904
NHS Fife	17,891
NHS Forth Valley	15,081
NHS Grampian	36,875
NHS Greater Glasgow and Clyde	88,382
NHS Highland	15,005
NHS Lanarkshire	32,416
NHS Lothian	56,078
NHS National Waiting Times	7,967
NHS Orkney	705
NHS Shetland	1,817
NHS Tayside	34,929
NHS Western Isles	1,704
Total	363,600

Sampling method

4.10 The sample size calculation was based on a 95% confidence level. The margin of error was set as +/- 5% which yielded results which would be accurate to within +/- 5% (increased to +/-7 percentage points in sites with less than 1,000 patients annually to avoid sampling too many patients in smaller sites).

4.11 Expected response rates within each NHS Board were calculated based on the response rates achieved by the 2011 Survey. These were used to adjust the required sample size for non-response.

4.12 The proportion of inpatients sampled at any hospital was limited to 60%. This avoids surveying too many patients from smaller hospitals, and is done to reduce costs as well as patient burden.

4.13 Table 3 shows that the total sample size allowing for non-response was 57,132, based on the requirement to achieve 29,485 completed returns for the stated accuracy.

Table 3 Required sample and total selected sample

NHS Board	Required sample	To allow for non-response	Proportion of inpatients sampled
NHS Ayrshire and Arran	3,847	7,554	18%
NHS Borders	617	1,105	18%
NHS Dumfries and Galloway	1,455	2,608	38%
NHS Fife	1,163	2,487	14%
NHS Forth Valley	729	1,572	10%
NHS Grampian	4,061	7,296	20%
NHS Greater Glasgow and Clyde	8,292	16,254	18%
NHS Highland	3,160	5,645	38%
NHS Lanarkshire	1,233	2,914	9%
NHS Lothian	1,950	3,839	7%
NHS National Waiting Times	696	1,392	17%
NHS Orkney	154	259	37%
NHS Shetland	318	576	32%
NHS Tayside	1,391	2,925	8%
NHS Western Isles	419	706	41%
Total	29,485	57,132	16%

NHS Boards sampling procedures

4.14 NHS Boards compiled a list of eligible patients appropriate for inclusion in the inpatient survey using a spreadsheet template provided by the Scottish Government. Detail to support this process was provided in the guidance manual for the inpatient survey as well as via liaison with Scottish Government staff.

4.15 Once a list of eligible patients was compiled, checks were undertaken by Boards to ensure that duplications, incomplete records, deceased patients and ineligible patients were not included in final proposed lists of patients.

4.16 Once compiled lists were checked and complete, Boards used the "Random" column function in Microsoft Excel to generate a random number between 0 and 1 for each sample record. The final sample was then selected by sorting randomly generated numbers in a random order and selecting the top listed patients by the required number within each stratum.

Sampling checks

4.17 In order to ensure that final sample was correct and accurate before survey packs were distributed, NHS Boards sent details of the proposed sample to their contractor who undertook quality assurance checks. For data protection purposes, the contractor did not receive any patient identifiable information - checks required Boards to provide overall profile of the patients in the eligible list and the profile of patients in the random drawn sample. Tables collected inpatient information relating to:

• Gender;
• Age;
• Month/year of admission;
• Month/year of discharge;
• Length of stay;
• NHS Board of residence;
• Hospital site and code; and
• Specialty code on discharge.

4.18 The contractor undertook a review of this anonymised aggregated information to ensure that sample was drawn correctly and that the final proposed sample was broadly representative of each Board's inpatient populations, with no unexplainable variances.

Data transfer

4.19 NHS Boards and Contractors were responsible for ensuring that all data was sent to and from NHS.net (NHSmail service) email accounts. The NHSmail service is a secure service and all information sent is encrypted whilst in transit. In addition, test emails were exchanged prior to sending any data to ensure the NHS.net addresses were correct.

4.20 All files were password protected when being transferred and delivery/read receipts were requested to ensure the information was received safely. All emails were kept for audit purposes.

4.21 On completion of the survey fieldwork and data capture (described in more detail in Chapters 5 and 6) the complete anonymised data files were sent electronically to ISD. This enabled ISD to undertake analysis for the reporting. In future, ISD will also be able to use the data files to link the survey responses of those patients who had given permission to do so with other health datasets for the purposes of exploring relationships between patient experience and health outcome.

Access to data

4.22 In accordance with the NHS ethical approval for the survey, contractors were given access to the names and addresses of the people who were to be sent the survey. All personnel were governed by the NHS Research Governance Framework for Health and Community Care. The survey guidance manual detailed the research governance responsibilities and accountabilities of all those involved in the survey.