Lab Reins in Magnesium Tests with Decision Support

Why It Matters

Reducing redundant magnesium testing cuts costs, frees lab capacity, and reinforces evidence‑based ordering across the health system.

Key Takeaways

• Magnesium test orders defaulted to daily in many order sets
• Half of inpatient magnesium orders were unnecessary repeats
• Decision support introduced soft alerts before hard stops
• Hard stops reserved for high‑risk tests like C. difficile
• Intervention aims to cut lab waste and improve stewardship

Pulse Analysis

Overordering of routine laboratory assays has become a hidden cost driver in many hospitals, and magnesium testing is a textbook example. At Washington University, a review of Epic order data revealed that 50% of inpatient magnesium draws were placed as automatic "AM daily" orders, often without any change in patient management. The test’s reference range and a low supplementation threshold further encouraged clinicians to order it reflexively, inflating test volume while providing little clinical benefit.

To address the issue, the laboratory team rolled out a layered decision‑support strategy. Initial measures included non‑interruptive alerts and brief order‑set questions that prompted clinicians to confirm the necessity of each repeat draw. Only if these softer nudges failed would the system consider a harder intervention, such as a hard stop—currently limited to high‑impact assays like Clostridioides difficile, where false positives can trigger costly reimbursement penalties. This graduated approach respects clinician autonomy while gradually shifting behavior toward more judicious ordering.

The broader implication for health systems is significant. By eliminating redundant magnesium tests, hospitals can reduce consumable expenses, lower patient blood‑draw burden, and free laboratory staff to focus on higher‑value analyses. Moreover, the success of this targeted intervention provides a template for tackling other overused tests, reinforcing a culture of laboratory stewardship that aligns with value‑based care initiatives and regulatory expectations.