Comparison of the defined daily dose and days of treatment methods for evaluating the consumption of antibiotics and antifungals in the intensive care unit

Objective: To compare the measurement of antimicrobial consumption by defined daily dose (DDD) versus by days of therapy (DOT). Design: Retrospective analysis of clinical and administrative data from patients admitted to a polyvalent ICU. Setting: ICU at a University Hospital in Spain. Patients: All patients admitted to the ICU. Interventions: None. Main variables of interest: For the DDD method, the World Health Organization (WHO)-assigned DDD was determined for the all the prescribed antimicrobials. For the DOT method, one DOT represented the administration of a single agent on a given day regardless of the number of doses administered. To express aggregate use, total DDDs and total DOTs were normalized to 100 patient-days. Results: During the study period, 2393 adult patients were admitted to the ICU. Total median antimicrobial drugs measured by DDDs was 535.3 (IQR 319.8-845.5) vs. 344.0 (IQR 117.2-544.5) when measured by DOTs, p < 0.001. When antimicrobial consumption was normalized to 100 patient-days, median antimicrobial consumption was also higher when measured by DDDs [2.98/100 patient-days (IQR 1.76-5.25) vs. 1.89/100 patient-days (IQR 0.64-3.0) when measured by DOTs, p < 0.001]. Conclusions: For most antibacterial and antifungal drugs used in critically ill patients, estimates of aggregate antibiotic use by DDDs per 100 patient-days and DOTs per 100 patient-days are discordant because the administered dose is dissimilar from the WHO-assigned DDD. DOT methods should be recommended to avoid the overestimation that occurs with DDDs in adult critically ill patients. (C) 2019 Elsevier Espana, S.L.U. y SEMICYUC. All rights reserved.