Investigators can correlate the sale of a particular kind of drug (over the counter or prescription) with the prevalence of an underlying condition.
In this study, researchers wanted to determine whether oral vancomycin sales were a useful marker for Clostridium Difficile Infection (CDI). CDI bacterium can cause potentially fatal infection that often affects older individuals in nursing homes and people in hospitals, many of whom have been treated with other antibiotics.
The researchers used population data on 88 Ohio counties and prescription data from retail pharmacy transactions from January 1999 to September 2007. They found an upward trend in CDI cases followed by a similar upward trend in vancomycin, beginning in 2002.
They acknowledge that vancomycin is not the only drug used to treat CDI, and that new drugs and intravenous vancomycin were not considered in their study. However, they conclude that prescription sales of vancomycin are a “reasonable proxy” for Clostridium Difficile Infection, and a relatively inexpensive form of surveillance for a disease that is of increasing importance to public health.