L-Tryptophan and Eosinophilia-Myalgia Syndrome ("EMS")

Leslie Swygert and Richard Dicker
Date published
Jan, 2011
Last updated
21 Jan 2020


National epidemic of new syndrome in 1989 quickly traced to a commercial product. Case study addresses surveillance, bias, criteria for causation.


  • Discuss issues related to rapid establishment of national surveillance for a newly recognized and little understood disorder
  • Discuss development of case definitions
  • Describe the elements of design and the advantages and disadvantages of case‑control versus cohort studies
  • Discuss some of the biases that might have affected these studies
  • Calculate and interpret a relative risk, odds ratio, and attributable risk percent
  • List and evaluate the criteria for causation