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Assessment of Antimicrobial Utilization Metrics: Days of Therapy Versus Defined Daily Doses and Pharmacy Dispensing Records Versus Nursing Administration Data

  • Bruce R. Dalton (a1) (a2), Deana M. Sabuda (a1), Lauren C. Bresee (a1) (a3) and John M. Conly (a2) (a4) (a5) (a6) (a7)



To compare antimicrobial utilization data derived from pharmacy dispensing records and nursing administration record data by 2 commonly used units of measure.


Data from nursing administration records and pharmacy dispensing records were obtained for 32 medical wards. From nursing and pharmacy data, defined daily doses (DDD) were calculated, and from the nursing data, days of therapy were derived. Direct comparison of total antimicrobial use was performed by graphical analysis and linear regression. Slope of trend line was used to quantify the difference between pairs of measures. Bland-Altman plots were constructed to determine constant and proportional bias. At the level of individual agents, difference between pairs of measures was calculated and presented graphically and the average (95% CI) for the difference between measures was determined.


Nursing administration record–derived DDD were on average 23% lower than corresponding rates of pharmacy dispensing record–derived DDD. The difference between rates of utilization by days of therapy vs DDD from the same source (nursing) was relatively small. Results from analysis of different individual agents were highly variable with wide 95% CIs.


In our setting, we found clinically relevant differences in antimicrobial utilization associated with data from different sources. This outweighed the importance of the metric (DDD or days of therapy). However, measurement of use of individual agents was highly variable and sensitive to both metric unit and data sources.

Infect Control Hosp Epidemiol 2015;00(0): 1–7


Corresponding author

Address correspondence to Bruce R. Dalton, PharmD, Clinical Pharmacy Office, Rm 1080, Foothills Medical Centre, 1403 29th St NW, Calgary, Alberta, Canada, T2N 2T9 (


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