Unit of measurement: (defined daily dose, DDD)
The World Health Organization Collaborating Center of Drug Statistics Methodology defined the DDD as the assumed average maintenance dose per day for a drug used in ist main indication in adults . It is a theoretical dose, a compromise between the dosage recommendations of various indications, fixed and regularly updated by the WHO. The DDD system measures the quantity of used drugs, independently of the dosage and the package size, which facilitates the comparisons of consumption between hospitals or countries .
The quantities in grams of antibiotics were converted in DDD and then expressed in DDD per 100 beddays (density of use). They are recommended by the WHO as the unit of measurement for drug utilization studies in the hospital care setting [3, 4]. According to the Federal Statistical Office, the beddays correspond to the number of days during which a person is hospitalized.
Data collection and results
Pharmacists were mainly recruited among members of the Swiss Society of Public Health Administration and Hospital Pharmacists (GSASA) because of their easy access to the data concerning the quantities of antibiotics delivered to the hospital units, setting up a sentinel network of acute care hospitals.
Data were provided for 50 hospitals (8 of which were grouped in 2 hospital networks) in 2004, 51 (8 were grouped in 2 hospital networks) in 2005 and 55 in 2006. Sentinel hospitals were stratified in 3 categories of size : less than 200 beds, between 200 to 500 beds and more than 500 beds. The density of use did not vary significantly between similar size hospitals (Figure 1).
Figure 1 : Global density of antibiotic use stratified by hospital size from 2004 to 2006, expressed in DDD per 100 beddays. The line in the box indicates the median value of the data set. The upper and the lower edges of the box represent the 75th and the 25th percentiles. The minimum and maximum data values are shown as capped bars.
* the hospital with the highest density of use in 2004 and 2005 changed the category in 2006, passing from < 200 beds' to 200 ' 500 beds' category.
The implementation of a sentinel network allowed to compare the use of the Swiss hospitals with the European countries . The present study showed that the global antibiotic use in the Swiss hospitals was close to the European median.
A detailled publication is in preparation.
 World Health Organization Collaboration Center for Drug Statistics Methodology. ATC index with DDDs. Oslo : World Health Organization, 2005.
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 Dukes MN. Drug utilization studies. Methods and uses. WHO Reg Publ Eur Ser 1993 ; 45 :1-4.
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