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.