James M. Hutchinson and Robert N. Foley have analysed data from the Newfoundland Drug and Medical Care plans and have concluded that factors other than medical indication, namely method of physician remuneration and patient volume, played a major role in determining antibiotic prescribing practices. [1] Unfortunately, their analysis is seriously flawed and cannot be used to make inferences about the rates of antiobiotic prescribing.
The main problem is that Hutchinson and Foley have chosen the wrong population for the denominator in calculating their rates. If one wishes to compute antibiotic prescribing rates in a practice, one should compute the number of prescriptions per patient visit or per patient attending the practice. Instead, they have computed the number of prescriptions per patient who received an antibiotic prescription. This statistic says very little about the overuse of antibiotics.
Consider an example: Suppose a colleague and I each have 100 patients in our practices, and 50 of them present each year with complaints of sore throat. I choose to prescribe an antibiotic to every patient who complains of a sore throat, writing 50 prescriptions in that year. According to the authors, my prescribing rate is thus 50 divided by 50 unique patients, which equals 1 per patient per year. My colleague diagnoses strep throat in 1 of the 50 patients visiting him and prescribes an antibiotic to him, but not to the other 49. That patient returns twice with recurrent strep throat and receives 2 more prescriptions. My colleague's prescribing rate is thus 3 prescriptions per unique patient per year. According to the authors' method, my prescribing rate is one-third of that of my colleague. Quite clearly, the authors' method does not lead to useful policy conclusions.
Murray M. Finkelstein, PhD, MD CM
Toronto, Ont.
References
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