Reducing overutilisation of serum vitamin D testing at a tertiary care centre

Abstract

Introduction: Testing of 25-hydroxy (25-OH) vitamin D serum levels has increased drastically in recent years and much of it is considered inappropriate based on current guidelines.

Methods: In consultation with our physician groups (experts and frequent orderers), we modified existing guidelines and implemented a rational policy for 25-OH vitamin D testing and 1,25 dihydroxy (1,25 di-OH) vitamin D testing at a tertiary care centre. A computer decision support tool requiring selection of one of five acceptable testing indications was created for each test as part of a computerised physician order entry system.

Results: As a result of our intervention, we observed a 27% decrease in the average monthly test volume for 25-OH vitamin D from 504±62 (mean±SD) tests per month to 370±33 (p<0.001). 1,25 di-OH vitamin D testing decreased 58% from 71±18 to 30±10 (p<0.001). The departments ordering the tests were similar during the preintervention and postintervention periods, and further audits, patient chart reviews and individualised physician feedback were required to ensure appropriate ordering of 1,25 di-OH vitamin D. The most common ordering reasons selected were malabsorption/dietary concerns (46%) for 25-OH vitamin D and renal failure (42%) for 1,25 di-OH vitamin D.

Conclusions: Limitations of our computer decision support tool include a dependence on an honour system in selecting the testing indication and an inability to limit ordering frequency. Periodic monitoring of test volumes will be required to ensure adherence to guidelines. Despite these limitations, we have improved appropriate utilisation of these tests and reduced costs by approximately $C60 375 per year.

Keywords: test utilization; vitamin D.

Figure 1

LHSC/SJHC testing policy for 25-OH vitamin D and 1,25 di-OH vitamin D, implemented within the CPOE system in Cerner Millennium. (A) Information pop-up window that appears when an order for 25-OH vitamin D is entered. This information is also associated with the orderable as reference text that can be consulted if someone needs more details before selecting the reason for ordering the test. (B) The drop-down menu of appropriate indications for testing that must be selected from to allow the order for 25-OH vitamin D testing to proceed. The choices were limited to 15 characters by Cerner Millennium. (C) The drop-down menu of appropriate indications for testing that must be selected from to allow the order for 1,25 di-OH vitamin D testing to proceed. The choices were limited to 15 characters by Cerner Millennium. (D) Information associated with the 1,25 di-OH vitamin D orderable as reference text that can be consulted if someone needs more details before selecting the reason for ordering the test. CPOE, computerised physician order entry; LHSC, London Health Sciences Centre; SJHC, St. Joseph’s Health Care London; 25-OH, 25-hydroxy; 1,25 di-OH, 1,25 dihydroxy.

Figure 2

Summary of steps taken to ensure appropriate ordering of 25-OH vitamin D and 1,25 di-OH vitamin D tests at LHSC/SJHC. CPOE, computerised physician order entry; LHSC, London Health Sciences Centre; SJHC, St. Joseph’s Health Care London; 25-OH, 25-hydroxy; 1,25 di-OH, 1,25 dihydroxy.

Figure 3

Test volumes for 25-OH vitamin D and 1,25 di-OH vitamin D during the preintervention period (January 1, 2016 to December 31, 2017) and the postimplementation of ordering restrictions period (February 1, 2018 to July 31, 2018). (A) Monthly test volumes for 25-OH Vitamin D. (B) Monthly test volumes for 1,25 di-OH vitamin D. (C) Average monthly test volumes and p values according to unpaired two-tailed t-tests. January 2018 was not included in the statistical analysis of monthly test volumes since the intervention occurred in January 15, 2018, in the middle of the month. 25-OH, 25-hydroxy; 1,25 di-OH, 1,25 dihydroxy.

Figure 4

Percentage of patients with orders for 25-OH vitamin D testing only (black bars), 1,25 di-OH vitamin D testing only (white bars), or both tests (grey bars), both in the preintervention period (January 1, 2016 to December 31, 2017) and the postintervention period (February 1, 2018 to July 31, 2018). 25-OH, 25-hydroxy; 1,25 di-OH, 1,25 dihydroxy.

Figure 5

(A) Percentage of patients with 25-OH vitamin D retested before or after 90 days who had a change or no change in category of result (deficiency: <25 nmol/L; insufficiency: 25–74 nmol/L; sufficiency: 75–250 nmol/L; and toxicity: >250 nmol/L). **P < 0.01 for retesting after 90 days or more compared with retesting before 90 days by two-tailed χ² test. (B) The percentage of patient 25-OH vitamin D results falling into each category during the preintervention and postintervention periods (monthly mean±SD). (C) The percentage of patient 1,25 di-OH vitamin D results falling into each category (low: <60 pmol/L; normal: 60–208 pmol/L; and high: >208 pmol/L) during the preintervention and postintervention periods (monthly mean±SD). 25-OH, 25-hydroxy; 1,25 di-OH, 1,25 dihydroxy.

Figure 6

Reasons for ordering 25-OH vitamin D or 1,25 di-OH vitamin D testing that were given following implementation of the ordering restrictions. PTH, parathyroid hormone; 25-OH, 25-hydroxy; 1,25 di-OH, 1,25 dihydroxy.