Detection of Pediatric Respiratory and Diarrheal Outbreaks from Sales of Over-the-counter Electrolyte Products
- William R Hogan, MD,
- Fu-Chiang Tsui, PhD,
- Oleg Ivanov, MD, MPH,
- Per H Gesteland, MD,
- Shaun Grannis, MD,
- J Marc Overhage, MD, PhD,
- J Michael Robinson, MA,
- Michael M Wagner, MD, PhD for the Indiana–Pennsylvania–Utah Collaboration
- Affiliations of the authors: The RODS Laboratory, Center for Biomedical Informatics, University of Pittsburgh, Pittsburgh, Pennsylvania (WRH, F-CT, OI, MMW); University of Utah and Intermountain Health Care, Salt Lake City, Utah (PHG); Regenstrief Institute, Indianapolis, Indiana (SG, JMO); Global Strategic Solutions, LLC, Cincinnati, Ohio (JMR), USA
- Correspondence and reprints: William R. Hogan, MD, Suite 8084 Forbes Tower, 200 Lothrop Street, Pittsburgh, PA 15213; e-mail: <wrh{at}cbmi.pitt.edu>.
- Received 4 April 2003
- Accepted 27 May 2003
Objective
To determine whether sales of electrolyte products contain a signal of outbreaks of respiratory and diarrheal disease in children and, if so, how much earlier a signal relative to hospital diagnoses.
Design Retrospective analysis was conducted of sales of electrolyte products and hospital diagnoses for six urban regions in three states for the period 1998 through 2001.
Measurements Presence of signal was ascertained by measuring correlation between electrolyte sales and hospital diagnoses and the temporal relationship that maximized correlation. Earliness was the difference between the date that the exponentially weighted moving average (EWMA) method first detected an outbreak from sales and the date it first detected the outbreak from diagnoses. The coefficient of determination (r2) measured how much variance in earliness resulted from differences in sales' and diagnoses' signal strengths.
Results The correlation between electrolyte sales and hospital diagnoses was 0.90 (95% CI, 0.87–0.93) at a time offset of 1.7 weeks (95% CI, 0.50–2.9), meaning that sales preceded diagnoses by 1.7 weeks. EWMA with a nine-sigma threshold detected the 18 outbreaks on average 2.4 weeks (95% CI, 0.1–4.8 weeks) earlier from sales than from diagnoses. Twelve outbreaks were first detected from sales, four were first detected from diagnoses, and two were detected simultaneously. Only 26% of variance in earliness was explained by the relative strength of the sales and diagnoses signals (r2 = 0.26).
Conclusion Sales of electrolyte products contain a signal of outbreaks of respiratory and diarrheal diseases in children and usually are an earlier signal than hospital diagnoses.
Footnotes
-
The authors thank Judith Hutman and Information Resources, Inc., the commercial provider of the retail data, for assistance in obtaining retail electrolyte data. The authors thank the Pennsylvania Health Care Cost Containment Council for supplying discharge data for this study and Dr. Robert Rolfs, Utah's State Epidemiologist, and Carol Masheter and John Morgan from the Utah Center for Health Data for providing data from the Utah Hospital Discharge Database. This work was supported by grants 2 T 15 LM0-7117-06, T15 LM/DE07059 and 01-T15/LM0724 from the National Library of Medicine; contract 290-00-0009 from the Agency for Healthcare Research and Quality; Pennsylvania Department of Health Award number ME-01-737; and contract F30602-01-2-0550 sponsored by the Defense Advanced Research Projects Agency and managed by Rome Laboratory. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the Defense Advanced Research Projects Agency, Rome Laboratory, or the United States Government.
