Laboratory testing of urine, stool, and blood is important for keeping track of infectious diseases as they spread throughout the country. Since 1996, the Food borne Disease Active Surveillance Network (FoodNet) has been tracking lab tests, and especially stool samples, which is where disease-causing bacteria are often found. They conducted a study several years ago to determine whether regional variations in disease prevalence were due to actual variations or just differences in the quality of testing done in labs.

What the researchers wanted to know: How consistent are the laboratories testing for food-borne illnesses?

What they did: FoodNet collected information on the lab practices of labs in 10 states and the rate of food-borne disease from those labs. They also sent a questionnaire asking about testing practices for six harmful bacteria to all of the labs in those states that participated in the surveillance, and about 90 percent, 388 labs, were used in the analysis.

What they found: Most labs routinely test for common food-borne pathogens such as salmonella, shigella, and campylobacter. However, much fewer, only 57 percent, routinely test for one harmful strain of E. coli (E coli 0157:H7) and the proportion of samples tested has declined since the survey was first done in 1995. The FoodNet researchers speculate that declines seen in the rate of campylobacter and shigella cases represent a true decline in illnesses but that the apparent decline in the cases of E. coli is because many labs don't test for it.

What it means to you: The authors recommend making a test for E. coli part of routine screening, or at the very least, testing patients with other symptoms.

Caveats: This study relied heavily on the labs' own reports, which could be flawed because labs may not keep detailed records.

Find out more: The Food and Drug Administration has a very colorful website with information about food safety and food-borne illnesses.

Information about FoodNet is available through the Centers for Disease Control and Prevention.

Read the article: Voetsch, A.C. et al. "Laboratory Practices for Stool-Specimen Culture and Bacterial Pathogens, Including Escherichia Coli 0157:H7, in the FoodNet Sites, 1995–2000." Clinical Infectious Diseases. April 15, 2004, Vol. 38, Supplement 3, pp. S190–S197.

Abstract online: www.journals.uchicago.edu