title: Vitamin D assessment in primary care: changing patterns of testing.
abstract: BACKGROUND
  Over recent years there has been increased interest in the disease burden associated with vitamin D deficiency. This, combined with recognition that the prevalence of vitamin D deficiency is high in the UK, has led to increased requests for vitamin D assessment from primary care clinicians.
  
  
  METHODS
  A primary care cohort in Liverpool.
  
  
  OBJECTIVE
  How has the usefulness of vitamin D testing changed over time in identifying deficiency?
  
  
  METHODS
  Vitamin D results from primary care practices in Liverpool were collected between 2007 and 2012, inclusive. Results were allocated to six cohorts based on year of request and each was grouped into three categories (adequate, insufficient and deficient).
  
  
  RESULTS
  Vitamin D results of 9460 (74%) first tests and 3263 (26%) retests were analysed. Total number of requests increased 11-fold, from 503 in 2007 to 5552 in 2012. Overall 42% of first-test results were deficient (< 30 nmol). With each incremental year, more cases of vitamin D deficiency were detected - but the odds of detecting vitamin D deficiency decreased.
  
  
  CONCLUSIONS
  An exponential increase in the number of vitamin D requests was observed over this six-year period. Although more patients with vitamin deficiency were identified, the increased number of tests represents a significant cost to health services. Moreover, the practice of retesting too soon after treatment can be inappropriate. There is a need to develop clear guidance for assessing vitamin D status in primary care.
authors.affiliation: Academic Clinical Fellow, Department of Rheumatology, Institute of Aging and Chronic Disease, University of Liverpool, UK.
authors.forename: Sizheng
authors.initials: S
authors.lastname: Zhao
authors.affiliation: General Practitioner, Liverpool Clinical Commissioning Group, UK.
authors.forename: Katy
authors.initials: K
authors.lastname: Gardner
authors.affiliation: Principal Clinical Scientist.
authors.forename: William
authors.initials: W
authors.lastname: Taylor
authors.affiliation: Consultant in Clinical Biochemistry and Metabolic Medicine Royal Liverpool and Broadgreen University Hospital NHS Trust, UK.
authors.forename: Eileen
authors.initials: E
authors.lastname: Marks
authors.affiliation: Senior Lecturer and Honorary Consultant in Rheumatology, Department of Rheumatology, Institute of Aging and Chronic Disease, University of Liverpool, UK.
authors.forename: Nicola
authors.initials: N
authors.lastname: Goodson
keywords: primary care; supplementation; testing; treatment; vitamin D