Advanced CKD Study

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Advanced CKD Study

• Daniel Ford
• UKRR Annual Audit MeetingJune 2009

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Overview

• Data collection issues
• Definition of the date of start of dialysis
• Pre-RRT study results
• Associations with the rate of kidney function
  decline in the final year pre-RRT

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Pre-RRT Study

• Objectives
• To look at what factors are associated with
• eGFR decline
• Hb decline
• Survival
• during the final year prior to starting RRT
• Methods
• 4,722 incident RRT patients from 7 centres from
  2001-2006
• Extracted laboratory data
• 0, 1, 2, 3, 4, 5, 6, 12 months pre-RRT

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n826
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• Distinction between acute and chronic HD
• Definition of start of PD

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Definition of acute HD

• Of 826 records checked, 14.9 started RRT on
  acute HD with no retrospective timeline change

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Definition of acute HD

• If a patient started as acute renal failure
  and did not recover, the date of start of renal
  replacement should have been backdated to the
  start of acute dialysis.

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Definition of acute HD

• Appendix B of Annual Report (online only)
• Methodology or instruction to clinicians?

• If a patient started as acute renal failure
  and did not recover, the date of start of renal
  replacement should have been backdated to the
  start of acute dialysis.

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Definition of start of PD

• 75/826 had some evidence of PD exchanges prior to
  documented start date
• What is the date of start of PD?

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Definition of start of PD

• 75/826 had some evidence of PD exchanges prior to
  documented start date
• What is the date of start of PD?
• Insertion of PD catheter?
• First fluid exchange after PD catheter?
• Date of start of CAPD training?
• Date of PD independence?

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Consequences of inaccurate RRT start date

• Dubious eGFR trend pre-RRT
• Existing eGFR at start studies
• Survival data
• Late presentation data

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What needs to be done?

• UKRR
• Redefine date of start of HD (acute/chronic)
• National
• Consensus on date of start of PD

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Date of start of HD

• If a patient started as acute renal failure and
  did not recover, the date of start of renal
  replacement should have been backdated to the
  start of acute dialysis. Many nephrologists do
  not do this and where this period of acute
  dialysis has been recorded in local systems, the
  UKRR will use this data to backdate the start of
  RRT.

Appendix B UKRR 11th Annual Report, December
2008
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Date of start of HD

• If a patient started as acute renal failure and
  did not recover, the date of start of renal
  replacement should have been backdated to the
  start of acute dialysis. Many nephrologists do
  not do this and where this period of acute
  dialysis has been recorded in local systems, the
  UKRR will use this data to backdate the start of
  RRT.

Appendix B UKRR 11th Annual Report, December
2008
Letter to RA membership C Tomson, M Raftery, 23rd
March 2009
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Date of start of HD

• If a patient started as acute renal failure and
  did not recover, the date of start of renal
  replacement should have been backdated to the
  start of acute dialysis. Many nephrologists do
  not do this and where this period of acute
  dialysis has been recorded in local systems, the
  UKRR will use this data to backdate the start of
  RRT.

Appendix B UKRR 11th Annual Report, December
2008
Letter to RA membership C Tomson, M Raftery, 23rd
March 2009
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Date of start of PD

• The date of start of peritoneal dialysis is
  defined as the date of first PD fluid exchange
  given with the intention of causing solute or
  fluid clearance
• This contrasts with an exchange solely for
  confirming or maintaining catheter patency. In
  general, exchanges which are part of PD training
  should be considered as the start of PD.

Chapter 7 Survival in UK RRT patients. UKRR 11th
Annual Report, December 2008
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Summary of timeline issues

• Inaccurate timeline returns are common
• This has implications for a number of UKRR
  analyses, including
• Survival
• Rates of late presentation
• eGFR at start of RRT
• This may not be unique to the UKRR
• Efforts are being made to re-define and publicise
  problematic definitions

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Pre-RRT Study Results
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Pre-RRT study

• 7 centres
• 2001-2006
• n4,722
• Excluded patients
• presenting late (lt3m)
• with missing data from relevant analyses
• with anomalous timeline data
• with fewer than 4 eGFR results

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eGFR statistical analyses- Retha Steenkamp

• Least-square analysis
• Linear regression line fitted on an
  individual-patient basis
• Mean rate of eGFR decline calculated
• Multi-level model
• Quadratic model
• Adjusted for
• Age, gender, ethnicity, PRD

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Results

• Age
• Ethnicity
• Primary renal disease
• Systolic BP
• Diastolic BP
• Time from first renal presentation

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Rate of eGFR decline pre-RRT by age group
(adjusted for gender, ethnicity and PRD) (95 CIs)

• Hunsicker LG, et al. Kidney Int
  1997511908-1919.
• Levin A, et al. American Journal of Kidney
  Diseases 200852661-671.
• Eriksen BO, et al. Kidney Int 200669375-382.

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Modelled eGFR pre-RRT by age group
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Modelled eGFR pre-RRT by age group
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Modelled eGFR pre-RRT by age group
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Modelled eGFR pre-RRT by age group
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Modelled eGFR pre-RRT by age group
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Rate of eGFR decline pre-RRT by ethnicity
(adjusted for age, gender and PRD) (95 CIs)

• McClellan W, et al. J Am Soc Nephrol
  2006171710-1715.
• Clase CM, et al. J Am Soc Nephrol
  2002131338-1349.
• Coresh J, et al. American Journal of Kidney
  Diseases 2003411-12.
• Hsu C-Y, et al. J Am Soc Nephrol
  2003142902-2907.

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Modelled eGFR pre-RRT by ethnicity (adjusted for
age, gender and PRD)
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Rate of eGFR decline pre-RRT by primary renal
disease (adjusted for age, gender and ethnicity)
(95 CIs)

• Hemmelgarn BR, et al. Kidney Int
  2006692155-2161.
• Levin A, et al. American Journal of Kidney
  Diseases 200852661-671.
• Jungers P, et al. Nephrol Dial Transplant
  1995101353-1360.

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Modelled eGFR pre-RRT by primary renal disease
(adjusted for age, gender and ethnicity)
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Rate of eGFR decline by systolic BP at 6 months
pre-RRT (adjusted for age, gender, ethnicity and
PRD) (95 CIs)
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Rate of eGFR decline by diastolic BP at 6 months
pre-RRT (adjusted for age, gender, ethnicity and
PRD) (95 CIs)
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Rate of eGFR decline pre-RRT by time from first
presentation (adjusted for age, gender, ethnicity
and PRD) (95 CIs)
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Modelled eGFR pre-RRT by time from first renal
presentation (adjusted for age, gender, ethnicity
and PRD)
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Discussion

• Limitations
• Retrospective, only includes patients on RRT
• Missing data
• Date first seen, PRD, ethnicity, BP, co-morbidity
• Timeline issues
• Strengths
• Largest study of patients in the final year
  pre-RRT (4,722 vs. 159 342)
• Unselected UK incident cohort

• Jungers P, et al. NDT 1995 10(8) 1353-60
  n159
• Ambrogi V, et al. Nephron Clin Prac 2009 111
  95-101 n342

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Summary of findings

• Associations with faster eGFR decline are
• Younger age
• Black and South Asian ethnicity
• GN diabetes
• Higher systolic and diastolic BP
• Late presentation

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Acknowledgements

• Statistics
• Retha Steenkamp
• Supervisors
• Damian Fogarty, Yoav Ben-Shlomo, Charlie Tomson,
  David Ansell
• Data collection
• David Bull, Andy Webb and the UKRR systems team
• UK renal centres and patients

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