Therapeutic drug monitoring (TDM) is a valuable tool for certain antifungals as it may increase the probability of a successful outcome, minimize drug-related toxicity and interactions, and potentially prevent emergent resistance. With an increasing emphasis on the need for antifungal and laboratory stewardship, we sought to review azole antifungal TDM practices at our institution.
This was a retrospective quality review of TDM at Cleveland Clinic Main Campus during a 6-month period (3/8/2017 9/8/2017), including all azole levels resulting during an inpatient admission. Levels were assessed for timing of collection, redundancy, indication, and characteristics of the patient and ordering service. Levels were further adjudicated as guideline-concordant (GC) or discordant (GD) according to published TDM guidelines (Fig. 1). Primary endpoint: percentage of GC azole levels. Secondary endpoints: indication for TDM, percentage of levels within range, actions taken following a level result, cost, and turnaround time.
Of 301 azole levels obtained, 184 (61%) and 117 (39%) were classified GC and GD (Fig3), respectively. GC and GD levels were collected a median 8 days (IQR 5-14) and 3 days (IQR 2-7) into therapy, respectively. GC levels were more likely to be within therapeutic range compared to GD levels (64% vs. 54%; p=0.076). The most common TDM indications were per lung transplant prophylaxis protocol and concern for absorption (Fig. 2). A total of 140 reasons for GD levels were found, with 54 (18%) being an improperly timed voriconazole trough, 39 (13%) redundant TDM orders, 37 (12%) not at steady state, and 10 (3%) with unjustified TDM. Of 117 GD levels, 35 (30%) resulted in antifungal modification within 48 hours, most commonly an increase in dose, n=12 (10%). Mean collection-to-result turnaround time was 1.6 days for all azole levels, and significant costs were attributed to GD levels.
Our review of azole TDM suggests a significant proportion of levels obtained are discordant with available TDM guideline recommendations with respect to timing and redundancy. This presents an opportunity to improve test utilization, antifungal-related outcomes, and clinician confidence when interpreting and acting upon concentration data.
E. Neuner, None
K. Rivard, None
E. Cober, None
A. McShane, None
G. W. Procop, None
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