Comparison of tWo hospital quality Improvement interventions on inappropriate measurement and SupplEmentation of vitamin D: the WISE-D study

Despite a lack of evidence, measurement and supplementation of vitamin D remain frequent in the general population, leading to significant and potentially avoidable healthcare costs. The aim of this study was to evaluate the impact of two quality improvement interventions (minimal vs. intensive) on inappropriate vitamin D measurement and supplementation in hospitalized patients and compare the two interventions. We conducted a pre-post intervention study on general internal medicine wards in Switzerland between 01 July 2016 and 31 December 2023. We compared a minimal intervention consisting of short guidelines in one hospital with a more intensive intervention including an e-learning, reminder e-mails and quizzes in a second hospital. Inappropriate measurement and supplementation of vitamin D were defined as measurement/supplementation in the absence of specific conditions associated with vitamin D deficiency (i.e., osteoporosis, osteomalacia, hepatic failure, malabsorption syndrome, chronic kidney disease with hyperparathyroidism, granuloma-forming disorders, or medications affecting vitamin D or bone metabolism). We used difference-in-differences with random-effects regression with bootstrap standard errors to estimate the overall intervention effect on inappropriate vitamin D measurement and supplementation across hospitals and compared the differences between hospitals. Among 31,755 hospitalizations, the average monthly percentage of inappropriate vitamin D measurement and supplementation were 4.0% and 20.5%, respectively, over the entire study period. Compared to the pre-intervention period, there was a 1.3% reduction in inappropriate vitamin D measurements after the start of the interventions ( p = 0.003), with no significant difference between interventions ( p = 0.98). However, the rate of inappropriate vitamin D supplementation did not significantly change after intervention start ( p = 0.81). Training interventions for residents were associated with a reduction in inappropriate vitamin D measurement, but not supplementation. The lack of significant difference between both interventions, even if not confirming equivalence, suggests that simpler, more passive strategies may be just as effective as more intensive approaches, offering a cost-efficient way to curb low-value care.