title: Trends in serum creatinine testing in Oxfordshire, UK, 1993-2013: a population-based cohort study.
abstract: OBJECTIVE
  To determine how many kidney function tests are done, on whom, how frequently they are performed and how they have changed over time.
  
  
  METHODS
  Retrospective study of all serum creatinine, urine albumin and urine creatinine tests.
  
  
  METHODS
  Primary and secondary care in Oxfordshire from 1993 to 2013.
  
  
  METHODS
  Unselected population of 1,220,447 people.
  
  
  METHODS
  The total number of creatinine and urinary protein tests ordered from primary and secondary care and the number of tests per year stratified by categories of estimated glomerular filtration rate (eGFR). The frequency of testing in patients having their kidney function monitored.
  
  
  RESULTS
  Creatinine requests from primary care increased steadily from 1997 and exceeded 220,000 requests in 2013. Tests corresponding to normal kidney function (eGFR >60/mL/min/1.73 m(2)) constituted 59% of all kidney function tests in 1993 and accounted for 83% of all tests in 2013. Test corresponding to chronic kidney disease (CKD) stages 3-5 declined after 2007. Reduced kidney function, albuminuria, male gender, diabetes and age were independently associated with more frequent monitoring. For a female patient between 61 and 80 years and with stage 3a CKD, the average number of serum creatinine tests (95% CI) was 3.23/year (3.19 to 3.26) and for a similar woman with diabetes, the average number of tests was 5.50 (5.44 to 5.56) tests per year.
  
  
  CONCLUSIONS
  There has been a large increase in the number of kidney function tests over the past two decades. However, we found little evidence that this increase is detecting more CKD. Tests are becoming more frequent in people with and without evidence of renal impairment. Future work using a richer data source could help unravel the underlying reasons for the increased testing and determine how much is necessary and useful.
authors.affiliation: Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK.
authors.forename: Jason
authors.initials: J
authors.lastname: Oke
authors.affiliation: Department of Clinical Biochemistry, John Radcliffe Hospital, University of Oxford, Oxford, UK.
authors.forename: Brian
authors.initials: B
authors.lastname: Shine
authors.affiliation: Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK.
authors.forename: Emily
authors.initials: E
authors.lastname: McFadden
authors.affiliation: Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK.
authors.forename: Richard
authors.identifier: http://orcid.org/0000-0002-9258-4060
authors.initials: R
authors.lastname: Stevens
authors.affiliation: Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK NIHR Oxford Biomedical Research Centre, John Radcliffe Hospital, Oxford, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: Lasserson
authors.affiliation: Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK.
authors.forename: Rafael
authors.initials: R
authors.lastname: Perera
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000419:Albuminuria / Q000652:urine*; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood* / Q000652:urine; D048909:Diabetes Complications / Q000097:blood; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007677:Kidney Function Tests / Q000639:trends*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011320:Primary Health Care; D051436:Renal Insufficiency, Chronic / Q000175:diagnosis* / Q000453:epidemiology*; D012189:Retrospective Studies; D006113:United Kingdom / Q000453:epidemiology; D055815:Young Adult
chemical_list: D003404:Creatinine
keywords: Chronic kidney disease; EPIDEMIOLOGY; PRIMARY CARE; serum creatinine