1737. Impact of Therapeutic Drug Monitoring (TDM) of Azole Prophylaxis in Lung Transplant Recipients on the Development of Positive Fungal Events

BACKGROUND: The utility and clinical impact of therapeutic drug monitoring (TDM) of prophylactic azole antifungals in lung transplant recipients is not well described. The objective of this study was to investigate the impact of TDM of azole prophylaxis in lung transplant recipients on the development of positive fungal events. METHODS: A retrospective analysis was performed on 47 lung transplant recipients between 2013 and 2018 at Northwestern Memorial Hospital. A positive fungal event was defined as fungal species on BAL culture and/or positive BAL Aspergillus galactomannan (GM) with an index value ≥1.0. Study groups were defined based on attainment of therapeutic trough levels after initiation of oral therapy (therapeutic if posaconazole level ≥0.7 μg/mL or voriconazole ≥1–5.5 μg/mL, subtherapeutic if ≥2 consecutive levels of posaconazole <0.7 μg/mL or voriconazole <1 μg/mL after initial dose increase). RESULTS: There were no differences in baseline characteristics (Figure 1). There were a total of 11 fungal events with 3 (12.0%) occurring in the therapeutic cohort and 8 (36.4%) in those subtherapeutic (P = 0.08). In the 5 patients with a positive GM, the mean index was 2.02 ± 0.95. 7/30 (23.3%) of patients on posaconazole had a fungal event, with 2/7 (28.6%) requiring treatment at the time of event. For patients on voriconazole, 4/17 (23.5%) had a fungal event, with 1/4 (25.0%) requiring treatment. Mean time to fungal event was 164.5 ± 8.9 days vs. 135.9 ± 13.7 days in the therapeutic and subtherapeutic group, respectively (P = 0.05). All patients on posaconazole suspension who experienced a fungal event were subtherapeutic (3/3, 100%) compared with the majority of patients on posaconazole delayed release (DR) tablets who achieved therapeutic levels (17/22, 77.3%). Mean posaconazole trough level observed in the patients receiving DR tablet was 2.15 ± 0.95 μg/mL. CONCLUSION: There was an association between two consecutive subtherapeutic azole prophylaxis levels and positive fungal events indicating a role for TDM in lung transplant recipients. Time to fungal event post-transplant was shorter in subtherapeutic patients. As anticipated, the use of posaconazole suspension resulted in subtherapeutic levels. This study presents an opportunity for further research of the impact of TDM on clinical outcomes to optimize patient care. [Image: see text] DISCLOSURES: All authors: No reported disclosures.