Patient outcome variables

2.4.6.1Emergency admission during diagnostic pathway

Every hospital inpatient spell or daycase procedure mode of admission is either elective or emergency and is a recoded variable in inpatients HES records (Syntax 11). In this study, method for determining emergency presentations (diagnosis) of cancer cases are identified according to the episode containing the index (first) diagnostic procedure (gastroscopy) as either elective admission (i.e. daycase gastroscopy) or non-elective admission (i.e. gastroscopy performed during an unplanned ‘emergency’ hospitalization).

The present study aimed to use the most relevant clinical care event (i.e. the first gastroscopy procedure) to identify the point of diagnosis of OG cancer within inpatient HES data. More recently, Eliss-Brook et al used both inpatient and/or outpatient HES activity data to attempt to establish an elective or emergency route of cancer diagnosis for a range of cancer types.[274] Although Eliss-brook used the same selection of admission method codes for elective (codes 11, 12 and 13) and emergency (codes 21, 22, 23, 24 and 28) admissions as the present study, their methodology selected any inpatient or outpatient event in closest proximity to the date of diagnosis as determined by linkage to cancer registration records extracted from the National Cancer Data Repository.[274-276] However, this approach did not identify whether these events included a specific diagnostic procedure for the

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cancer in question – thereby examining all-cause events rather that a defined clinical milestone in the patient journey.

The present study identifies an unplanned emergency diagnosis of cancer as representing the following categories of patient: (1) those admitted to hospital having never seen their GP and were diagnosed with cancer; (2) Patients who were very ill, or who had abnormal results, who had contacted their GP or the out of hours service, and were then admitted to hospital; and (3) patients who might be seen by their GP and were referred routinely or via a two-week wait, but who deteriorated before their scheduled appointment and were admitted to hospital and then diagnosed with cancer.

This defines the mode of diagnosis as either elective or emergency. Once the mode of ‘’diagnosis’’ has been identified, it is re-linked according to HESID to be visible as the mode of diagnosis for every admission within the dataset, through use of the SPSS function DATA > MERGE FILES > ADD VARIABLES. It is important to note that any outcome measure used throughout this study (otherwise stated) has a value of 1 if the admission was emergency (unplanned), and 0 if not.

2.4.6.2Surgery

Surgical intervention for oesophago-gastric cancer was defined on the basis of coding a major surgical resection compatible with curative intent, using a list of previously reported OPCS-4 codes (Appendix 7 [277], Syntax 12). Additional steps were undertaken to identify these surgical codes in specialist surgical centres (hospitals other than the 152 acute trusts). For example, major resections happen at the Cardiothoracic Centre-Liverpool NHS Trust (RBQ) includes cases which were

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originally diagnosed at the Royal Liverpool and Broadgreen University Hospitals NHS Trust (RQ6). The identified surgical episodes through this procedure were then added to final analysis. Every cancer patient was classified as either having had a record of a major surgical resection or not. Where a patient might have a record of more than one OPCS surgical code allocated as a major resection for their treatment, these cases were only once in the analyses as they received a curative resection.

2.4.6.3Mortality

The index diagnostic gastroscopy date was taken as the starting point or “provisional diagnosis date’’ for survival analysis, and mortality rates were calculated at various post gastroscopy time points (e.g. 30 days, 6 months and one year mortality) using death dates linked from the Office of National Statistics. The SPSS function used to record the number of days in between these two landmarks was [TRANSFORM > DATE AND TIME WIZARD > CALCULATE WITH DATES AND TIMES > CALCULATE THE NO. OF TIME UNITS.] (Syntax 13). It is important to note that patients with no death date were censored to the 31/03/2009, which was the last death (follow up) date coded among the ONS death data.

2.4.7 Gastroscopy procedures coded as in-patient or day-case procedure under

adult medical and surgical specialties

Using the previously described two-year download of the HES dataset containing more than 24 million care episodes (2006/7 and 2007/8), all hospital episodes containing a procedure code for diagnostic gastroscopy for adult patients (≥16 years) were extracted using published procedure codes and definitions [266, 267]

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(Appendix 4, Syntax 4). The process of ensuring that no duplicate procedure is included within the extracted data was achieved by using SPSS function (DATA > Identify duplicate cases > Define matching cases by > HESID, Admission date, DIAG01, DIAG02, PROCEDURE1, PROCEDURE2, GPCODE, EPIEND “Episode end date” and Consultant code “ CONSCD”).

In England, all residents receiving NHS healthcare are registered with a general practice that comprises one or more family doctors providing primary care services to a defined practice population. Each general practice has an identifier code within HES. All gastroscopy procedures were recorded for persons registered at each general practice, via aggregate function within SPSS.

Published data are available for the total number of adult patients (≥16 years) registered at each general practice, their gender and age profile for the relevant years.[278-280] The average counts of elective gastroscopies performed per practice per year were calculated. This value was divided by the relevant practice adult population to give an annualised crude rate of gastroscopy. To ensure that differences in the number of events (e.g. gastroscopy rate) observed in two or more populations (GP practices) were not due to differences in the age and sex profile, data for the practice population demographic profile [278], was measured alongside the Indirect age and sex standardization (or adjustment) of rates [281].

102 Indirect standardisation method summary:

I. Calculate the number of OGD procedure related to every practice by 5 year age bands (15-19), (20-24),...(80-84) and (>=85); and for males and females of the same age bands (15-19)m, (20-24)m,...(80-84)m, (>=85), (15-19)f, (20-24)f,...(80-84)f, and (>=85)f. These are the ‘’observed events’’.

II. Calculate the reference event (total number of OGD procedures for the included practices) and reference population (total number of adult population registered in all practices in the study).

III. reference crude rate (OGD rate for England) = reference Event/reference Population*100,000

IV. Calculate the local (every practice) expected events= reference rate/practice population

V. The standardization ratio= the observed events / expected events.

VI. The indirect age-sex standardized OGD rate= standardized ratio*reference

Crude rate/100.