A tutorial on aphasia test development in any language: Key substantive and psychometric considerations.

BACKGROUND: There are a limited number of aphasia language tests in the majority of the world's commonly spoken languages. Furthermore, few aphasia tests in languages other than English have been standardized and normed, and few have supportive psychometric data pertaining to reliability and validity. The lack of standardized assessment tools across many of the world's languages poses serious challenges to clinical practice and research in aphasia. AIMS: The current review addresses this lack of assessment tools by providing conceptual and statistical guidance for the development of aphasia assessment tools and establishment of their psychometric properties. MAIN CONTRIBUTION: A list of aphasia tests in the 20 most widely spoken languages is included. The pitfalls of translating an existing test into a new language versus creating a new test are outlined. Factors to consider in determining test content are discussed. Further, a description of test items corresponding to different language functions is provided, with special emphasis on implementing important controls in test design. Next, a broad review of principal psychometric properties relevant to aphasia tests is presented, with specific statistical guidance for establishing psychometric properties of standardized assessment tools.
CONCLUSIONS: This article may be used to help guide future work on developing, standardizing and validating aphasia language tests. The considerations discussed are also applicable to the development of standardized tests of other cognitive functions.