Test–retest reliability of the Danish Adult Reading Test in patients with comorbid psychosis and cannabis-use disorder

Abstract

Background: The New Adult Reading Test is a common instrument for assessing pre-morbid IQ for patients with, for instance, schizophrenia. However, test–retest reliability has not been established for patients dually diagnosed with psychosis and substance use disorder. Furthermore, test–retest reliability of the Danish adaptation has never been established in any population. Aims: To determine the test–retest reliability of the Danish Adult Reading Test (DART) (adapted from the National Adult Reading Test, NART) for patients dually diagnosed with psychosis and cannabis-use disorder. Methods: This was a secondary analysis of the CapOpus randomized trial. As part of the trial, 103 patients were randomized, and completed the DART up to three times. Pearson's r and pairwise t-tests were calculated. Results: DART score was independent of randomization, cannabis-use frequency and psychopathology. Scores at the last interview were slightly higher than at the first two. Correlation over time was very strong (0.8 < r <0.9) for all pairwise comparisons of interviews. Variations in DART scores and estimated pre-morbid IQ over time were sometimes of borderline statistical significance but not of clinical relevance. Conclusions: DART and NART have high test–retest reliability, but apparently non-systematic, clinically irrelevant variation over time does occur. Clinical implication: The Danish adaptation of the New Adult Reading Test possesses good test–retest reliability, making it an appropriate choice for assessment of pre-morbid IQ, and in patients with dually diagnosed psychosis and cannabis-use disorder.

• Cannabis
• Danish Adult Reading Test
• dual diagnosis
• psychosis
• schizophrenia
• test–retest reliability

Acknowledgements and disclosure of interest—Funding for this study came from funds and grants supporting the CapOpus trial, specifically supplied by: The Lundbeck Foundation, The Municipality of Copenhagen, The Egmont Foundation, The Health Insurance Foundation, The Ministry of Social Welfare, Aase and Ejnar Danielsen’s Foundation, and the Wørzner Foundation. The authors have no conflicting interests, and the foundations etc. providing funds and grants were not involved in any manner in design and conduct of the study; collection, management, analysis and interpretation of the data; or preparation, review or approval of the manuscript. The authors would like to thank our colleagues at the Mental Health Center Copenhagen for invaluable insight and support in the conduct and analysis of the CapOpus trial. Finally, we thank the 103 participants of the CapOpus trial.

The authors alone are responsible for the content and writing of the paper.