Trough drug levels in narrow therapeutic index medications, such as CNI and mTOR inhibitors are used to estimate total drug exposure. Inappropriately measured trough levels in the acute care setting provide no value to patient care and may result in errors in drug dosing, while also generating unnecessary costs for the health-system. This study evaluates the appropriateness of immunosuppression trough levels to determine the cost burden to the health system and identify potential future interventions to ensure levels are drawn appropriately.

This was a retrospective single center cohort study of CNI (tacrolimus, cyclosporine) and mTOR inhibitor (sirolimus, everolimus) trough levels in the acute care setting of an academic medical center from July 1, 2017 – July 31, 2017. Appropriateness was based on level orders in the electronic health record matching drug orders and timeliness of level ordering and collection. The primary objective was to determine the incidence of inappropriate levels and the associated monthly and projected annual costs of level waste. Due to logistical challenges in the large academic medical center, a trough level >8 hours was considered appropriate. The median trough length of <8-h troughs was compared by impacting action using a non-parametric median test.

552 levels were analyzed, with 12.9% (n=71) inappropriate resulting in $16,685 and $200,220 in monthly and projected annual costs, respectively. Inappropriate levels occurred due to: troughs <8-h 36.6% (n=26), randomly ordered 25.4% (n=18), ordered for the wrong drug 23.9% (n=17), peak drug level 7% (n=5), duplicate levels 2.8% (n=2), >2 per week mTOR level orders 1.4% (n=1). Late drug administration (n=4), early level collection (n=11), or both actions (n=11) resulted in 26 trough levels <8-h (n=26). Late drug administration and early level collection resulted in significantly lower trough levels vs. either factor alone (7.48-h vs 6.98-h, p=0.015). Of the 18 random tacrolimus levels ordered, 8 were from the emergency department.

Inappropriate immunosuppression trough levels represent a significant cost burden to the institution of over $200,220 with an average transplant volume of 200 recipients per year. Potential interventions to reduce inappropriate levels include: renaming drug level orders as 'Troughs' or 'Random' with required indications for random levels, leveraging clinical decision support to ensure appropriate timing.

CITATION INFORMATION: Brown A., Geyston J., Agarwal A., Jones B., Ally W. Evaluation and Cost Burden of Inappropriately Drawn Immunosuppression Trough Levels in the Acute Care Setting at an Academic Medical Center Am J Transplant. 2017;17 (suppl 3).

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