Appropriateness of tacrolimus therapeutic drug monitoring timing in the emergency department.

PURPOSE: Evaluate the appropriateness of the timing of serum samples collected in the emergency department (ED) for tacrolimus (TAC) measurement. METHODS: Single-center, retrospective review of TAC samples collected in the ED from September 1 to October 31, 2017. The primary evaluation was incidence of inappropriate sample collection for TAC measurement, defined as samples not collected 12 h (±2 h; 10-14 h) after the last dose, or within 2 h of the next dose if last known dose time was not documented. Incidence of repeat TAC measurements obtained within 24 h of ED presentation (if initial sample collection inappropriate), inappropriate TAC regimen adjustments, and healthcare costs of inappropriate TAC measurements was evaluated. Data collection included patient demographics, ED visit information, TAC measurement and timing related to last or next dose, changes to TAC regimen, and ED disposition. Descriptive data are reported. RESULTS: Sixty-two patients were included. Forty-one (66%) initial TAC measurements were collected inappropriately in the ED. No patients had a regimen adjustment as a result of inappropriate concentration collection, but 32 patients (78%) did require a repeat measurement within 24 h of ED presentation due to initial inappropriate collection. Costs associated with incorrectly collected TAC measurements were $2,647.78 for the two-month time period and this is extrapolated to an estimated $15,886.68 annual expense for patients. CONCLUSIONS: Inappropriate sample collection for TAC measurements was common in the ED, resulting in frequent repeat laboratory draws and increased healthcare costs.