A Comparison of Appendicectomy Outcomes in Children Between Paediatric and General Surgical Centres in Scotland
Condition: Appendicitis
MeSH terms: Appendicitis
Study type: Observational

Summary: 
      Introduction

      Appendicectomy (or appendectomy in US usage) is the single most commonly performed emergency
      surgical operation performed on British children. Previous investigation of outcomes
      following appendicectomy has suggested that specialist surgeons and high volume centres have
      fewer "negative" appendicectomies (i.e. the appendix found to be non-diseased), although
      there has not been consistent association found between hospital type or surgeon experience
      and complication rate or admission rate.

      Scotland has 3 dedicated children's surgery centres but straightforward children's surgery
      such as appendicectomy is also carried out in the country's general surgical centres.
      Appendicectomy outcome variations have not been explored in the Scottish National Health
      Service (NHS).

      Aim

      This study will compare appendicectomy outcomes in children between Scotland's specialist
      paediatric centres and general surgical centres.

      Methods

      This is a retrospective study of all appendicectomies performed in Scotland during the period
      from 1st January 2001 - 31st December 2010, on children aged 2 - 12 years old. It will use
      routinely collected administrative data from the Information Services Division of NHS
      National Services Scotland.

      The study will compare risk-adjusted 30 day/in-patient mortality, 30 day re-admission rate,
      30 day re-operation rate, post-operative length of stay and negative appendicectomy rates.
    

Detailed description: 
      The aim of this study is to compare Scottish appendicectomy outcomes in children between
      specialised paediatric centres versus non-specialised centres.

      This is a retrospective study of all appendicectomies performed in Scotland during the period
      from 1st January 2001 - 31st December 2010, on children aged 2 - 12 years old or younger. It
      will use routinely collected administrative data from the Information Services Division (ISD)
      of NHS National Services Scotland.

      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 Disease (ICD)-10
      standards and procedures are coded according to the United Kingdom's Office of Population
      Census Statistics (OPCS) standards, of which the most current 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.

      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 1:1. 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 548 was required to
      demonstrate this difference.

      In the last epidemiological study of appendicitis in Scotland (Bisset AF. Appendicectomy in
      Scotland: a 20-year epidemiological comparison. J Public Health. 1997 Jun 1;19(2):213-8),
      1522 appendicectomies in 1993 were performed in children aged 0-15 years old. This suggests
      that a 10 year cohort should be more than adequate to detect a clinically significant
      difference in length of stay.

      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 will compare risk-adjusted 30 day/in-patient mortality, 30 day re-admission rate,
      30 day re-operation rate, post-operative length of stay and negative appendicectomy rates
      between Scotland's specialist paediatric centres and general surgical centres.

      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.
    

Observational model: Ecologic or Community
Time perspective: Retrospective
Sampling method: Probability Sample
Study population: 
        All children resident in Scotland, who undergo appendicectomy during the study period
        specified.
      
Biospecimen description: 
      Please note that the investigators are not yet in receipt of the database required for this
      study. Although the study period has ended, we are not able at present to state how many
      patient episodes this database has captured.
    
Keywords: Outcome Assessment (Health Care); Appendectomy; Child; Hospitals, Pediatric; Hospitals, General