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Does Ascertainment Bias Affect Reports on the Incidence of Multidrug-Resistant, Community-Associated Methicillin-Resistant Staphylococcus aureus Infection?
- Kenneth A. Katz, MD, MSc, MSCE;
- Kyle T. Bernstein, PhD, ScM; and
- Jeffrey D. Klausner, MD, MPH
- From the Centers for Disease Control and Prevention, Atlanta, GA 30333, and San Francisco Department of Public Health, San Francisco, CA 94103.
TO THE EDITOR:
In their population-based survey (1), Diep and colleagues report a higher incidence of a multidrug-resistant, community-associated, methicillin-resistant Staphylococcus aureus (MRSA) clone USA300 infections in the San Francisco ZIP code that includes the Castro district, compared with San Francisco overall (170 vs. 26 cases per 100 000 persons, respectively) during 2004 to 2005. We are concerned that this finding reflects, at least in part, ascertainment bias rather than a true difference in disease incidence.
Diep and colleagues defined cases of infection as clinical cultures other than nasal swabs that were positive for multidrug-resistant, community-associated MRSA USA300. Clinical considerations determined whether cultures were performed. Because all …
