Sales of Popular Meds Early Indicator of Disease Outbreaks

Daniel M. Keller, PhD

July 05, 2012

July 5, 2012 (Bangkok, Thailand) — From sales data of a large pool of popular pharmacy medications, Chinese researchers narrowed down the list to a select subset that were an early indicator of outbreaks of infectious disease, notably influenzalike and gastrointestinal illnesses.

Presenting a poster here at the 15th International Congress on Infectious Diseases (ICID), lead investigator Yu Miao, a master's degree student in biostatistics and epidemiology in the School of Public Health of Fudan University in Shanghai, China, said sales of medications in pharmacies have been used as an early indicator of outbreaks of infectious diseases. In pharmacies with electronic sales and inventory systems, monitoring sales is fairly simple. But in pharmacies in less developed rural areas, collecting such data is most often done by hand and is a huge burden on staff. Therefore, the researchers set out to determine whether a manageable subset of medications could correlate with the larger set and predict outbreaks.

From August 1, 2011, through January 2012, the researchers tracked sales of 119 medications in 5 categories in 2 county pharmacies and 7 township pharmacies in a rural province in southeastern China. In pharmacies without electronic sales systems, pharmacy staff, mainly sales assistants, recorded sales figures by hand and entered them into a Web-based platform each day.

The medications comprised 39 compound cold medications, 39 cough suppressants, 18 antibiotics, 8 antipyretics, and 15 antidiarrheals. Data were compiled in 3 groups — 1 for each of the 2 county pharmacies and 1 for all of the township pharmacies together because of their lower sales volumes. The researchers ranked the medications by sales volume in descending order in each category until the rankings accounted for 70% of the sales volume for that category.

One Fifth of Medications Were Representative of Total Sales

Of the 119 medications, 26 (21.8%) accounted for two thirds (66.2%) of the total sales volume of all the pharmacies. The 26 medications included 7 of the 39 compound cold medications, 9 of the 39 cough suppressants, 3 of the 18 antibiotics, 3 of the 8 antipyretics, and 4 of the 15 antidiarrheals. Compared with the complete set in each category, the Pearson correlation coefficients were all greater than 0.84, and 4 of the 5 were greater than 0.90 (all P < .001).

The authors concluded that 26 medications could represent the original set of 119 medications with a high degree of correlation. Therefore, this smaller set of the most popular and representative medications makes it feasible for pharmacies in less developed rural areas to provide surveillance for outbreaks of flulike and gastrointestinal illnesses.

Importantly, Yu told Medscape Medical News, when data from pharmaceutical sales were compared with hospital data on symptoms of fever or cough, the researchers found a good correlation. "So we can combine these 2 data sources into a live picture and compare the relationship between the data from the pharmacy and the data from the hospitals," she said. Yu added that the pharmacy data appear to give about a 3-day advance signal of a disease outbreak.

Testing of the surveillance system in rural areas of China will continue into next year, and if the system continues to pan out, the researchers then plan to introduce it into practice.

Agnes Tomayao, a public health specialist and epidemiology coordinator in the Philippine Armed Forces Research Institute of Medical Sciences in Cebu City, the Philippines, observed the poster and wondered whether a similar system could be employed in her country.

"I think for one thing it depends on the context. For example, in my country, it would be difficult for us to get data on over-the-counter drug sales" directly from retail pharmacies, she commented to Medscape Medical News. "Maybe you can concentrate on some sentinel [pharmacies] — all these big companies — and then you can track them and get a sort of an idea of how the drugs are being distributed by them."

Tomayao said local and regional pharmaceutical distributors in the Philippines have computer systems to track inventories, so although they are one step removed from the retail pharmacies, they may be a good source of sales data for over-the-counter medications.

The study did not receive commercial support. Yu and Tomayao have disclosed no relevant financial relationships. Future Position X, a cluster organization, provided Geographic Information System services.

15th International Congress on Infectious Diseases (ICID). Abstract # 41.062. Presented June 14, 2012.

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