Does the use of a speech interpreter affect neuropsychological assessment?

In the United States, 67.86 million people speak a language other than English at home. Many also speak English, but not all are fluent. About 25.70 million people (8% of the U.S. population) report speaking, reading, or writing English “less than well” or “not at all.” These people are described as having Limited English Proficiency (LEP) and often need interpreters when they receive health care or other services. Neuropsychologists often assess LEP patients with the help of a speech interpreter. However, most clinicians believe this is not the best way to assess a patient’s abilities. We test this by looking at LEP patient test scores and clinical judgments and comparing them to similar patients. We predicted that using an interpreter would make neuropsychological test results less accurate. We compared 132 Spanish-dominant LEP patients tested with interpreters to 264 matched English-speaking patients. We also compared 33 Spanish-dominant LEP patients tested directly by Spanish-speaking clinicians to 66 matched English-speaking patients. Results supported our predictions. LEP patients tested with interpreters scored lower on neuropsychological tests than matched English-speaking patients (p < .001) and clinicians were less certain in their written conclusions (p < 0.001). Patients also showed greater spread in their test scores (p < 0.001). In contrast, no meaningful differences appeared when LEP patients were tested directly by Spanish-speaking clinicians. Overall, these results suggest that using interpreters during neuropsychological testing can make results less clear and less reliable. When possible, LEP patients should be tested by clinicians who speak the patient’s preferred language.