Validity of Diabetes
Prevalence from Health Data
Simon Thornley, Craig Wright, Roger Marshall,
Gary Jackson, Paul L Drury,...
Outline

  Diabetes prevalence

  Routine data

  Accuracy
    
        Compare to primary care
        database

   ...
Diabetes Prevalence

  Rapid increase last
  30 years

  Time trends
    
      Health Planning
    
      Primary Pre...
Surveys

  e.g. 2005 NZHS

  Not frequent

  Limited by selection
  bias (e.g. 70%
  response)

          Simon Thornle...
Health data
Linked by NHI
Dispensing, Diagnoses, Labs,
 Mortality, GP.
Improved quality since 2006,
 >90% NHI linkage
...
Algorithm
   Record review

   Diabetes if:
     5+ HbA    last two years
             1c
     Hospital ICD(1998-2008)...
Aim

  Assess validity of
 derived diabetes
 prevalence

  Compare to Primary
 care cohort
 (PREDICT) Wing
      Simon T...
“Gold Standard”
 PREDICT TM CVD RISK
 GP entered diagnosis.
 >100,000('00-'10)

 54,000 enter '07-'08
 Upper North Is...
Agreement?

  PREDICT vs.
  Algorithm?

  Sensitivity,
  Specificity, Kappa

  Capture-Recapture
          Simon Thornl...

    Recording of diabetes status?




            Simon Thornley, Wing
      Cheuk Chan, Paul Drury, Rod Jackson
Results

  PREDICT: 53,911

  20% Pac, 16% Maori

  Diabetes prevalence
  
    20.1% Algorithm
  
    20.9% PREDICT
 ...
Results

  Good agreement

  Sens~86% P(A+|P+)

  Spec~96% P(A-|P-)

  Kappa~85%

  Capture-Recapture
    
      ~15...
Agreement Diagram
  Total


Algorithm




PREDICT   Simon Thornley, Wing
    Cheuk Chan, Paul Drury, Rod Jackson
Summary

 Algorithm is
 accurate

 High level
 agreement

 Cheap, cost-
 effective method
     Simon Thornley, Wing
   ...
Thank You
      Dr Simon Thornley, Lecturer,
          University of Auckland
Section of Epidemiology and Biostatistics
  ...
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Predict and diabetes

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Predict and diabetes

  1. 1. Validity of Diabetes Prevalence from Health Data Simon Thornley, Craig Wright, Roger Marshall, Gary Jackson, Paul L Drury, Susan Wells, James Smith, Wing Cheuk Chan, Romana Pylypchuk, Rod Jackson. NZSSD Conference Apr 2010 Simon Thornley, Wing Cheuk Chan, Paul Drury, Rod Jackson
  2. 2. Outline  Diabetes prevalence  Routine data  Accuracy  Compare to primary care database  Capture-Recapture  Diagnosed vs undiagnosed
  3. 3. Diabetes Prevalence  Rapid increase last 30 years  Time trends  Health Planning  Primary Prevention efficacy
  4. 4. Surveys  e.g. 2005 NZHS  Not frequent  Limited by selection bias (e.g. 70% response) Simon Thornley, Wing Cheuk Chan, Paul Drury, Rod Jackson
  5. 5. Health data Linked by NHI Dispensing, Diagnoses, Labs, Mortality, GP. Improved quality since 2006, >90% NHI linkage Similar overall prevalence to survey results (Smith 2010) Simon Thornley, Wing Cheuk Chan, Paul Drury, Rod Jackson
  6. 6. Algorithm  Record review  Diabetes if:  5+ HbA last two years 1c  Hospital ICD(1998-2008)  Diabetes clinic ('04-'08)  Dispensing ('01-'08) Simon Thornley, Wing −insulin/oral hypo Cheuk Chan, Paul Drury, Rod Jackson
  7. 7. Aim  Assess validity of derived diabetes prevalence  Compare to Primary care cohort (PREDICT) Wing Simon Thornley, Cheuk Chan, Paul Drury, Rod Jackson
  8. 8. “Gold Standard”  PREDICT TM CVD RISK  GP entered diagnosis.  >100,000('00-'10)  54,000 enter '07-'08  Upper North Island Simon Thornley, Wing Cheuk Chan, Paul Drury, Rod Jackson
  9. 9. Agreement?  PREDICT vs. Algorithm?  Sensitivity, Specificity, Kappa  Capture-Recapture Simon Thornley, Wing Cheuk Chan, Paul Drury, Rod Jackson
  10. 10.  Recording of diabetes status? Simon Thornley, Wing Cheuk Chan, Paul Drury, Rod Jackson
  11. 11. Results  PREDICT: 53,911  20% Pac, 16% Maori  Diabetes prevalence  20.1% Algorithm  20.9% PREDICT  23.7% Capture-recap Simon Thornley, Wing Cheuk Chan, Paul Drury, Rod Jackson
  12. 12. Results  Good agreement  Sens~86% P(A+|P+)  Spec~96% P(A-|P-)  Kappa~85%  Capture-Recapture  ~15% undercount in Algorithm  ~10% undercount in PREDICT Simon Thornley, Wing Cheuk Chan, Paul Drury, Rod Jackson
  13. 13. Agreement Diagram Total Algorithm PREDICT Simon Thornley, Wing Cheuk Chan, Paul Drury, Rod Jackson
  14. 14. Summary  Algorithm is accurate  High level agreement  Cheap, cost- effective method Simon Thornley, Wing Cheuk Chan, Paul Drury, Rod Jackson
  15. 15. Thank You Dr Simon Thornley, Lecturer, University of Auckland Section of Epidemiology and Biostatistics s.thornley@auckland.ac.nz www.slideshare.net/sithor Simon Thornley, Wing Cheuk Chan, Paul Drury, Rod Jackson

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