Clinical trial NCT02017951: Geographic Influences on Appendicectomy Outcomes
Official title: Geographic Influences on Appendicectomy Outcomes
Study type: OBSERVATIONAL
Overall status: COMPLETED
Conditions: Appendicitis
Keywords: Appendectomy
Hospitals,General
Hospitals,Rural
Hospitals,Urban
Rural Health Services
Geography, Medical
Outcome Assessment (Health Care)
Lead sponsor: University of Edinburgh
Sponsor class: OTHER
First posted: 2013-12-23
Enrollment: 40000
Sex: ALL
Standard ages: CHILD
ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Observational model: ECOLOGIC_OR_COMMUNITY
Time perspective: RETROSPECTIVE
Sampling method: PROBABILITY_SAMPLE
Study population: All Scottish residents undergoing appendicectomy during the study period.

Brief summary: Introduction

Appendicitis is a common condition which represents a significant resource burden for the Scottish National Health Service (NHS). It is unknown whether there are significant differences in outcomes following appendicectomy which may be explained by geographic factors.

Aims

The aim of this study is to describe appendicectomy outcomes in Scotland as they vary by the urban-rural nature of the patient's home location and travel time from hospital.

Methods

This research study is a retrospective observational enquiry which will utilise administrative data from the Information Services Division (ISD) of NHS National Services Scotland. Patient episodes will be identified by a procedure code for appendicectomy, and the urban-rural classification of patients will be derived from postcode data. Travel time from hospital will also be estimated through postcode data. The investigators will study a 10 year period from January 2001 to December 2010.

Primary outcome measures will be risk-adjusted 30 day/inpatient mortality, 30 day readmission rate, 30 day re-operation rate, length of stay and negative appendicectomy rates.

Detailed description: The aim of this study is to explore the possibility that outcome from appendicectomy may vary according to:

1. the urban-rural nature of the patient's home location and
2. travel time from hospital.

This is a retrospective study of all appendicectomies performed in Scotland during the period from 1st January 2001 - 31st December 2010. It will use routinely collected administrative data from the Information Services Division (ISD) of NHS National Services Scotland.

Potentially significant confounding variables such as age, gender, and co-morbidity will be studied for their predictive value in a univariate model and included in a multivariate model if they remain significant.

There is no single appendicectomy outcome measure which is a literature standard, so all of the following will be evaluated as primary outcome measures: risk-adjusted 30 day/inpatient mortality, 30 day readmission rate, 30 day re-operation rate, length of stay and negative appendicectomy rates.

The registry which will supply the data for this study is the Scottish Morbidity Record 01 (SMR01), the full title of which is the "General / Acute Inpatient and Day Case dataset" (see http://www.adls.ac.uk/nhs-scotland/general-acute-inpatient-day-case-smr01/?detail). SMR01 is collated and administered by ISD, and data submission is mandatory for all Scottish NHS providers of in-patient or day-case care. Approximately 1.4 million records are added each year. Diagnoses are coded according to International Classification of Diseases (ICD)-10 standards and procedures are coded according to the United Kingdom's Office of Population Census Statistics (OPCS) standards, the most recent of which is version 4.5.

The data quality in SMR01 is high and is assured by regular internal audits. In the 2010 audit of accuracy, Main Condition was recorded with an accuracy of 88% and Main Procedure was recorded with an accuracy of 94%. Where data inconsistencies are identified in the extract supplied for this study, further clarification will be obtained where possible with ISD's data retrieval support team. Data completeness is very high in SMR01. However, where significant volumes of data are missing or unusable, the need for data imputation will be explored.

The study period was decided on pragmatically by a desire to provide an assessment of current practice, fully within the era of widely practised laparoscopic surgery. A power calculation also suggested that this would provide an adequate sample size to demonstrate differences.

Our power calculation- specific to length of stay- was based on Faiz O, Clark J, Brown T, Bottle A, Antoniou A, Farrands P, et al. Traditional and Laparoscopic Appendectomy in Adults. Ann Surg. 2008 Nov;248(5):800-6. In their cohort of 259,735 appendicectomies performed from 1996-2006, the geometric mean length of stay was 3.52, with SD 1.8. We decided that a difference of 0.5 days would be 'clinically significant'. We specified alpha 0.05 and Power 0.9, and an allocation ratio of 2 (allowing comparison of one tertile to two others). A two-sided t-test of difference between two independent means was performed in G\*Power 3.1.7. This demonstrated that a total N of 616 was required to demonstrate this difference. According to ISD figures, there were 3,712 appendicectomy procedures performed in 2010/11, so with numbers available we will be able to detect a clinically significant difference in length of stay.

The investigators will use the Scottish government's own 8-fold urban-rural classification system (see http://www.scotland.gov.uk/Topics/Statistics/About/Methodology/UrbanRuralClassification) to investigate the possible relationship between patient geographical location and outcome. Urban-rural categories may be grouped for analysis, depending on initial exploratory work.

The investigators will further calculate the approximate travelling time from patient home location (using postcode) to the treating hospital, by constructing isochrones at time/distance intervals from hospitals. Travel time will be evaluated as a continuous and discrete variable.

Eligibility criteria: Inclusion Criteria:

* All patients, of all ages, undergoing appendicectomy (OPCS code H01) during the time period January 2001 - December 2010.

Exclusion Criteria:

* Patients undergoing appendicectomy for whom this is incidental to a more major abdominal procedure.
* Patients non-resident in Scotland.

Primary outcomes:
measure: Post-operative length of stay
timeFrame: From date of appendicectomy to date of discharge (whole days) - see below
measure: Re-operation
timeFrame: Within the index admission or within 30 days of discharge
measure: Re-admission
timeFrame: Within 30 days of index discharge
measure: Mortality
timeFrame: Either within 30 days of procedure, or during continuous in-patient stay
measure: Negative Appendicectomy Rate
timeFrame: At time of index procedure
Secondary outcomes:
Other outcomes:
Locations:
city: Multiple Locations
country: United Kingdom
facility: All Scottish NHS Hospitals
Study officials:
affiliation: University of Edinburgh
name: Ewen M Harrison, FRCS, PhD
role: PRINCIPAL_INVESTIGATOR
References: