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Purpose: The objective of this study is to assess the psychometric properties and reliability of the Swedish Patient-Reported Outcomes Measurement Information System (PROMIS) item banks for anxiety and depressive symptoms with item response theory analysis and post-hoc computerized adaptive testing in a combined Swedish Child and Adolescent Psychiatry (CAP) and school sample.

Methods: Participants (n = 928, age 12–20) were recruited from junior and high schools and Child and Adolescent Psychiatry Clinics in the region of Västerbotten. Unidimensionality, local independence, and monotonicity was tested. We fitted a graded response model to the data and tested differential item functioning (DIF) for sex, age group, sample type, and language (Swedish vs. U.S.). Moreover, a post-hoc computer adaptive testing (CAT) simulation was performed. All analysis were made in R.

Results: Unidimensionality, local independence, and monotonicity were acceptable. The graded response model yielded acceptable item fit, discriminative, and threshold values for all items in both item banks. DIF for language (Swedish vs. U.S.) was found for two items from the anxiety and one item from the depressive symptoms item banks. A Stocking-lord transformation was used for the items displaying language DIF, and post-hoc CAT simulations were performed. The post-hoc CAT simulation showed reliability around 0.9 for both Swedish and official U.S. item parameters T-scores calibration from within normal limits to severe anxiety and depressive symptoms.

Conclusion: The Swedish pediatric PROMIS item banks of anxiety and depressive symptoms are appropriate to assess mild to severe symptoms of anxiety and depressive symptoms in Swedish school- and CAP samples.