Geographic Influences on Appendicectomy Outcomes

NCT ID: NCT02017951

Last Updated: 2024-05-21

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

COMPLETED

Total Enrollment

40000 participants

Study Classification

OBSERVATIONAL

Study Start Date

2001-01-31

Study Completion Date

2013-08-31

Brief Summary

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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

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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.

Conditions

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Appendicitis

Study Design

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Observational Model Type

ECOLOGIC_OR_COMMUNITY

Study Time Perspective

RETROSPECTIVE

Study Groups

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Urban-Rural Classification 1: Large Urban Areas

Settlements of over 125,000 people.

No interventions assigned to this group

Urban-Rural Classification 2: Other Urban Areas

Settlements of 10,000 to 125,000 people.

No interventions assigned to this group

Urban-Rural Classification 3: Accessible Small Towns

Settlements of between 3,000 and 10,000 people and within 30 minutes drive of a settlement of 10,000 or more.

No interventions assigned to this group

Urban-Rural Classification 4: Remote Small Towns

Settlements of between 3,000 and 10,000 people and with a drive time of over 30 minutes to a settlement of 10,000 or more.

No interventions assigned to this group

Urban-Rural Classification 5: Very Remote Small Towns

Settlements of between 3,000 and 10,000 people and with a drive time of over 60 minutes to a settlement of 10,000 or more.

No interventions assigned to this group

Urban-Rural Classification 6: Accessible Rural

Areas with a population of less than 3,000 people, and within a 30 minute drive time of a settlement of 10,000 or more.

No interventions assigned to this group

Urban-Rural Classification 7: Remote Rural

Areas with a population of less than 3,000 people, and with a drive time of over 30 minutes to a settlement of 10,000 or more.

No interventions assigned to this group

Urban-Rural Classification 8: Very Remote Rural

Areas with a population of less than 3,000 people, and with a drive time of over 60 minutes to a settlement of 10,000 or more.

No interventions assigned to this group

Travel Time - see below

Travel time will be analysed as both a continuous and discrete variable.

No interventions assigned to this group

Eligibility Criteria

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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.
Eligible Sex

ALL

Accepts Healthy Volunteers

No

Sponsors

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University of Edinburgh

OTHER

Sponsor Role lead

Responsible Party

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Responsibility Role SPONSOR

Principal Investigators

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Ewen M Harrison, FRCS, PhD

Role: PRINCIPAL_INVESTIGATOR

University of Edinburgh

Locations

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All Scottish NHS Hospitals

Multiple Locations, , United Kingdom

Site Status

Countries

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United Kingdom

Other Identifiers

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XRB13069-GA

Identifier Type: -

Identifier Source: org_study_id

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