title: The need for improved identification and accurate classification of stages 3-5 Chronic Kidney Disease in primary care: retrospective cohort study.
abstract: BACKGROUND
  Around ten percent of the population have been reported as having Chronic Kidney Disease (CKD), which is associated with increased cardiovascular mortality. Few previous studies have ascertained the chronicity of CKD. In the UK, a payment for performance (P4P) initiative incentivizes CKD (stages 3-5) recognition and management in primary care, but the impact of this has not been assessed.
  
  
  RESULTS
  Using data from 426 primary care practices (population 2,707,130), the age standardised prevalence of stages 3-5 CKD was identified using two consecutive estimated Glomerular Filtration Rates (eGFRs) seven days apart. Additionally the accuracy of practice CKD registers and the relationship between accurate identification of CKD and the achievement of P4P indicators was determined. Between 2005 and 2009, the prevalence of stages 3-5 CKD increased from 0.3% to 3.9%. In 2009, 30,440 patients (1.1% unadjusted) fulfilled biochemical criteria for CKD but were not on a practice CKD register (uncoded CKD) and 60,705 patients (2.2% unadjusted) were included on a practice CKD register but did not fulfil biochemical criteria (miscoded CKD). For patients with confirmed CKD, inclusion in a practice register was associated with increasing age, male sex, diabetes, hypertension, cardiovascular disease and increasing CKD stage (p<0.0001). Uncoded CKD patients compared to miscoded patients were less likely to achieve performance indicators for blood pressure (OR 0.84, 95% CI 0.82-0.86 p<0.001) or recorded albumin-creatinine ratio (OR 0.73, 0.70-0.76, p<0.001).
  
  
  CONCLUSIONS
  The prevalence of stages 3-5 CKD, using two laboratory reported eGFRs, was lower than estimates from previous studies. Clinically significant discrepancies were identified between biochemically defined CKD and appearance on practice registers, with misclassification associated with sub-optimal care for some people with CKD.
authors.affiliation: Primary Care Clinical Sciences, NIHR School of Primary Care Research, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Poorva
authors.initials: P
authors.lastname: Jain
authors.affiliation: Primary Care Clinical Sciences, NIHR School of Primary Care Research, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Melanie
authors.initials: M
authors.lastname: Calvert
authors.affiliation: Department of Renal Medicine, Queen Elizabeth Hospital Birmingham, University Hospital Birmingham, Birmingham, United Kingdom; Division of Immunity and Infection, Medical School, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Paul
authors.initials: P
authors.lastname: Cockwell
authors.affiliation: Department of Primary Care Health Sciences, NIHR School of Primary Care Research, University of Oxford, Oxford, United Kingdom.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: McManus
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood; D019468:Disease Management; D005260:Female; D005919:Glomerular Filtration Rate; D006301:Health Services Needs and Demand; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011320:Primary Health Care / Q000592:standards*; D058996:Quality Improvement; D012042:Registries; D051436:Renal Insufficiency, Chronic / Q000175:diagnosis / Q000453:epidemiology*; D012189:Retrospective Studies; D012307:Risk Factors; D006113:United Kingdom / Q000453:epidemiology; D055815:Young Adult
chemical_list: D003404:Creatinine