An article published by the American College of Pediatrics listed certain types of errors interpreters make:

  • Omission: not interpreting a word or phrase
  • Addition: adding a word or phrase not uttered
  • Substitution: substituting a word or phrase for a different word or phrase
  • Editorialization: providing ones own views as the interpretation of a word or phrase
  • False fluency: using a word or phrase that does not exist in the language or is incorrect and substantially alters the meaning.

In this study, there was an average of 31 errors per interpreting encounter.  18% of the errors had potential clinical consequences overall. However, the percentage of errors with potential clinical consequences varied significantly.

Another study, published in the Annals of emergency Medicine, study noted that the years of experience made no difference. Only training made a difference.

  • Ad hoc interpreter: 22%
  • No interpreter: 20%
  • Professional interpreter with 40 to 99 hours of training: 12%
  • Professional interpreter with at least 100 hours of training: 2%. For interpreters with over 100 hours of training, 0% of the false-fluency, substitution or editorialization errors had potential clinical consequences.

Another study by the University of Massachusetts Medical School has found that professional interpreting services at both admission and discharge reduced a patient’s length of stay by 0.75 to 1.45 days. These patients were also less likely to be readmitted within 30 days.

The savings in misdiagnosis, length of stay and readmission rates are significant. In Oregon, the average cost per inpatient day is approximately $2500. Working with an interpreter, from this perspective, is very cost-effective.