3  Study Design

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This is a retrospective study comparing the outcome of kidney transplant patients allocated in the Eurotransplant Senior Program (ESP) with the outcome of kidney transplant recipients of similar age allocated via the standard Eurotransplant kidney allocation system (ETKAS; Control).

Based on the definition of the ESP and the 2 Control groups (see 3.1 and 3.2), Eurotransplant provided data for a total of n=3456 patients transplanted between 4 January 1999 and 4 January 2004. For reasons detailed in 6.2, 25 patients were excluded from the analysis populations, giving a total of 3431 evaluable patients.

3.1 ESP- Group

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Background information on the ESP can be found in section 1.1.5.

The study group (ESP group; old to old) consists of n=1406 patients. Patients in this group fulfil the criteria listed in the table below:

Table 3: ESP- eligibility criteria

recipient

age > 65 years

non-immunized at time of match (< 5% PRA)

first transplant*

donor

age > 65 years

allocation

local / regional

disregard HLA matching

based on waiting time and ABO compatibility only

*inclusion criteria were changed later on to also allow for second transplant

3.2 Control groups

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There are two different Control groups based on either donor or recipient age. Donor organs in both Control groups were allocated via ETKAS that mandates exchange for zero-mismatched kidneys and allocates all other kidneys based on a combination of the number of HLA mismatches, chance of a good HLA match (mismatch probability), waiting time, expected cold ischemia time (distance between donor and recipient centre) and kidney exchange between participating countries (De Meester, et al., 1998).

Control group 1

Control group 1 consists of recipients of all age groups who received an organ from a donor aged 65 years or older via ETKAS. This Control group is relatively small (n= 446 pts) with most patients being transplanted in the first 2 years (1999-2001) before the ESP became part of the ETKAS. Control group 1 is of importance when analyzing parameters linked to the impact of donor age on outcomes.

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Control group 1 (old to any) consists of n=446 patients

Control group 2

Control group 2 consists of recipients aged 60 to 64 years who received an organ from a donor of any age via ETKAS. The recipient age group of 60-64 years was selected for being the closest to the recipient age of the ESP patients. The size of this Control group is comparable to the size of the ESP group.

↓25

Control group 2 (any to old) consists of n=1687 patients

Due to the definition of the two Control groups there is an overlap of 109 patients between Control 1 and 2 ( )

3.3 Participating Centres

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All 64 renal transplant centres in the Eurotransplant region transplanted patients that fulfilled the criteria of at least one Control group were contacted and asked to provide missing and additional information. 50 centres representing >80% of patient data provided missing and additional data for the analysis.

For the first two years of the program (4 January 1999 to 4 January 2001) participation of the centres was on a strictly voluntary basis. As of 4 January 2001, the ESP became part of the ETKAS (Smits, et al., 2002). In the first year of the program N= 42 centres transplanted within the ESP, an additional 18 centres joined the program as of the second year. In total, N = 60 centres contributed ESP patients over the 5 year period 1999-2004.

3.4 Data capture

Eurotransplant maintains its own database (ENIS) that contains most of the information required for this analysis. However, only about 60% of the fields in ENIS had been completed and some additional parameters such as information on co-morbidities and hospitalizations, details of rejection episodes, immunosuppressive treatment and long term follow up were needed to allow for a more reliable and detailed analysis.

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A user-friendly data collection tool based on an ACCESS 97 database was created and pre-populated with the existing data from the Eurotransplant database (ENIS), and new fields for the additional parameters were created. Centres were asked to complete the blank fields electronically. An introductory letter from Prof. Frei and Guido Persijn, the ETKAC secretary, was sent to all 64 ET centers on 2 November 2004 informing them about the project, introducing me as the responsible contact person and asking for their support. The database was closed on 15 May 2005. The completed database was transferred to (ENIS) and all copies of the database used for analysis within the working group were deleted (local copies remained).


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