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Cognitive tests predict real-world errors: the relationship between drug name confusion rates in laboratory-based memory and perception tests and corresponding error rates in large pharmacy chains
  1. Scott R Schroeder1,
  2. Meghan M Salomon2,
  3. William L Galanter3,
  4. Gordon D Schiff4,
  5. Allen J Vaida5,
  6. Michael J Gaunt5,
  7. Michelle L Bryson6,
  8. Christine Rash6,
  9. Suzanne Falck3,
  10. Bruce L Lambert1
  1. 1Center for Communication and Health, Department of Communication Studies, Northwestern University, Chicago, Illinois, USA
  2. 2Department of Psychology, Northwestern University, Evanston, Illinois, USA
  3. 3Department of Medicine, University of Illinois, Chicago, USA
  4. 4Department of General Medicine, Brigham and Women's Hospital, Boston, Massachusetts, USA
  5. 5Institute for Safe Medication Practices, Horsham, Pennsylvania, USA
  6. 6Department of Pharmacy Practice, University of Illinois at Chicago, Chicago, Illinois, USA
  1. Correspondence to Dr Scott R Schroeder, Northwestern University, 710 North Lake Shore Drive, Chicago IL 60611, USA; schroeder{at}


Background Drug name confusion is a common type of medication error and a persistent threat to patient safety. In the USA, roughly one per thousand prescriptions results in the wrong drug being filled, and most of these errors involve drug names that look or sound alike. Prior to approval, drug names undergo a variety of tests to assess their potential for confusability, but none of these preapproval tests has been shown to predict real-world error rates.

Objectives We conducted a study to assess the association between error rates in laboratory-based tests of drug name memory and perception and real-world drug name confusion error rates.

Methods Eighty participants, comprising doctors, nurses, pharmacists, technicians and lay people, completed a battery of laboratory tests assessing visual perception, auditory perception and short-term memory of look-alike and sound-alike drug name pairs (eg, hydroxyzine/hydralazine).

Results Laboratory test error rates (and other metrics) significantly predicted real-world error rates obtained from a large, outpatient pharmacy chain, with the best-fitting model accounting for 37% of the variance in real-world error rates. Cross-validation analyses confirmed these results, showing that the laboratory tests also predicted errors from a second pharmacy chain, with 45% of the variance being explained by the laboratory test data.

Conclusions Across two distinct pharmacy chains, there is a strong and significant association between drug name confusion error rates observed in the real world and those observed in laboratory-based tests of memory and perception. Regulators and drug companies seeking a validated preapproval method for identifying confusing drug names ought to consider using these simple tests. By using a standard battery of memory and perception tests, it should be possible to reduce the number of confusing look-alike and sound-alike drug name pairs that reach the market, which will help protect patients from potentially harmful medication errors.

  • Patient safety
  • Medication safety
  • Human factors
  • Human error

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:

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