Design of a national retail data monitor for public health surveillance
The National Retail Data Monitor receives data daily from 10,000 stores, including pharmacies, that sell health care products. These stores belong to national chains that process sales data centrally and utilize Universal Product Codes and scanners to collect sales information at the cash register. The high degree of retail sales data automation enables the monitor to collect information from thousands of store locations in near to real time for use in public health surveillance. The monitor provides user interfaces that display summary sales data on timelines and maps. Algorithms monitor the data automatically on a daily basis to detect unusual patterns of sales. The project provides the resulting data and analyses, free of charge, to health departments nationwide. Future plans include continued enrollment and support of health departments, developing methods to make the service financially self-supporting, and further refinement of the data collection system to reduce the time latency of data receipt and analysis.
The rapid, early detection of disease outbreaks has become a national priority and an emerging field of research.1 Kaufmann et al.,2 after analyzing several bioterrorism scenarios, concluded that “delay in starting a prophylaxis program is the single most important factor leading to increased loss of life and health.” The urgency of the problem is reflected in an explosion of research on new computer-based disease surveillance systems.3,4,5,6,7,8,9,10,11,12
Wagner et al.1 recently discussed four possible ways to improve the earliness of outbreak detection. Prominent among them is the use of new types of surveillance data that track sales of over-the-counter (OTC) health care products such as cough syrup that are purchased early in the course of illness by sick individuals for the symptomatic treatment of illness. For common syndromes such as upper respiratory illness (“flu”) and asthma, the sick are more likely to self-treat with OTC health care products than to see a physician. In a random digit dialing survey of 1,505 individuals conducted by the Consumer Healthcare Products Association in 2001, 72% (505 of 701) of those with cough, cold, “flu,” or sore throat in the previous six months treated themselves with an OTC health care product. Importantly, in 42%, purchase or use of OTC preparations was their first action, and in 34%, self-observation was the first action.13 In less than 9% was seeking professional medical care the first action. For the symptom of headache, the findings were even stronger (81% self-medication and 52% self-observation, respectively, with 4% seeking a physician as the first action).13 In a population-based survey of 42,333 adults in the province of Ontario, Canada, only 14% of adults with upper respiratory tract infections visited a doctor, whereas 76% engaged in self-care with OTC medications.14 Sales of OTC health care products have attractive characteristics for outbreak detection. In the United States, use of scanners and Universal Product Codes at checkout counters in retail industry stores facilitates routine collection of such data in real time. A small number of national companies own the majority of retail outlets that sell such products, and these corporations integrate their sales data at the national level in near to real time. For these reasons, the technical effort and cost to obtain these data for public health surveillance are comparatively low.
Preliminary studies suggest that sales of OTC health care products can be used for the early detection of outbreaks,15,16,17 yet research progress has been slow due to the difficulty in obtaining data to adequately test the hypothesis in a sufficiently large number of sizable outbreaks. The first such study, reported in 1979, showed an association between influenza B activity and purchases of cold remedies for a single outbreak.17 A recent study of 18 seasonal outbreaks in children showed that sales of pediatric electrolyte solutions correlated strongly with hospitalizations of children for gastrointestinal and respiratory illnesses and usually preceded the hospitalizations by more than two weeks.15 Unpublished research shows increases in sales of OTC “flu” and cough preparations preceding increases in influenza activity as measured by outpatient billing diagnoses.16 Other research (conducted by our laboratory and others) simulates the effects of outbreaks of different magnitudes and time courses on sales of OTC health care products (and other types of data) to understand the smallest increase in sales that would be detectable above background levels of sales.18,19
A rationale for not monitoring nonspecific data such as sales of OTC health care products as a means of alerting has been presented by Broome et al.,20 who raise concerns that data with low specificity will require an increment of hundreds of units over baseline levels before detection would occur, and that the cost of investigating false alarms may be too high.
Because of the threat of bioterrorism, the relative ease and low cost of monitoring sales of OTC health care products, and the accumulating evidence in favor of monitoring sales of OTC health care products, the Real-time Outbreak and Disease Surveillance (RODS) laboratory worked with the retail industry to build a retail data monitor for the Commonwealth of Pennsylvania. The authors quickly realized that the same effort could create a National Retail Data Monitor. This report describes the design and current status of the National Retail Data Monitor.