DRUG UTILIZATION 90-PERCENT - A SIMPLE METHOD FOR ASSESSING THE QUALITY OF DRUG PRESCRIBING

Objectives: To describe a simple method for assessing the quality of d rug prescribing. Methods: We tested the idea that the number of drugs accounting for 90% of drug use - drug utilization 90% (DU90%) - may se rve as an indicator of the quality of drug prescribing. We ranked the drugs by volume of defined daily doses (DDD) and determined how many d rugs accounted for the DU90% segment. We also compared this segment wi th the pharmacotherapeutic guidelines issued by the Regional (local) D rug Committee to determine the adherence to its recommendations (index of adherence). The cost per DDD within the DU90% segment and for the remaining 10% was also calculated. The utilization of drugs based on p rescriptions purchased during April 1995 was determined for 24 primary health care (PHC) centres in southwestern Stockholm. Results: The num ber of different products, defined as all products marketed under a si ngle brand name within an ATC (anatomic therapeutic chemical) category , in the DU90% segment varied twofold (81-164) between the 24 PHC cent res. Differences in the number of GPs per PHC centre accounted for a t hird of this variation. The compliance with the Drug Committee recomme ndations varied between 54% and 78%. There was no relationship between the number of products accounting for the DU90% segment and the adher ence to local prescription guidelines, i.e. prescribing more products did not increase the adherence. The costs for the DU90% drugs varied f rom 2.26 SEK/DDD in one PHC centre to 3.75 in another one, with an ave rage cost of 2.87 SEK/DDD, while for the remaining 10% it was the doub le (6:54 SEK/DDD). In all, the DU90% drugs made up 80.8% of the total cost as compared with 19.2% for the remaining 10%. In the DU90% segmen t, there was no clear relationship between adherence to the guidelines and the cost!DDD, i.e. following the evidence-based guidelines appear ed to provide a higher quality of prescribing rather than cheaper pres cribing. Conclusions: The DU90% is an inexpensive, flexible, and simpl e method for assessing the quality of drug prescribing in routine heal th care. The number of products in the DU90% segment and adherence to proscription guidelines may serve as general quality indicators. The m ethod may be adapted to provide comparative data between PHC centres, hospitals, regions etc. that may be cross-sectional and longitudinal. Other quality criteria, specific for each class of drugs, should compl ement these general indicators.