Key Points Question What is the association of a multifaceted intervention aimed at changing the mindset of caregivers with the amount of unnecessary laboratory testing? Findings In this before-after quality improvement study conducted in the internal medicine departments of 4 large teaching hospitals in the Netherlands, the volume of laboratory tests ordered per patient contact was reduced in all 4 departments by 11.4% overall. In contrast, volume increased by 2.4% in 19 comparable hospitals in the Netherlands. Meaning The approach used in this study can be used as a framework for future projects aiming to reduce unnecessary laboratory diagnostic tests in routine clinical practice.

Objectives Inappropriate use of laboratory testing remains a challenging problem worldwide. Minimum retest intervals (MRI) are used to reduce inappropriate laboratory testing. However, their effectiveness and the usefulness in reducing inappropriate laboratory testing is still a matter of debate. The aim of this study was to evaluate the effectiveness of broadly implemented MRIs as a means of reducing inappropriate laboratory test requests. Methods We performed a retrospective study in a general care and teaching hospital in the Netherlands, where MRI alerts have been implemented as standard care since June 7th 2017. Clinical chemistry test orders in adult internal medicine patients placed between July 13th 2017 and December 31st 2019 were included. The primary outcome was the effectiveness of MRIs, expressed as percentages of tests ordered and barred as a result of MRIs. Results Of a total of 218,511 test requests, 4,159 (1.90%) got an MRI alert. These MRIs were overruled by physicians in 21.76% of the cases. As a result of implementing MRIs, 3,254 (1.49%) tests were barred. The financial savings for the department of internal medicine directly related to the included barred laboratory tests during this period were 11,880 euros on a total amount of 636,598 euros for all performed tests. Conclusions Only a small proportion of laboratory tests are barred after implementation of MRIs, with a limited impact on the annual costs. However, MRIs provide a continuous reminder to focus on appropriate testing and the effectiveness of MRIs is potentially higher than described in this study.