Content validation using Aiken methodology through expert judgment of the first Spanish version of the Eppendorf...

The main objective of this study was the validation through the expert judgment of the first Spanish version of the Eppendorf Schizophrenia Inventory (ESI-Sp).

A translation and cultural adaptation procedure as a first stage was carried out, which was evaluated by four psychiatrists with clinical experience. In a second stage, we recruited a group of clinical psychiatrists to evaluate the translated instrument by judging the items' clarity and relevance. Content validity was performed using the Aiken methodology (Aiken's V).

For the first stage, we did not find any items that needed alteration during translation and adaptation. Concerning the raters' stage, 30 clinical psychiatrists (47.07±13.62 years) completed the rating of the ESI-Sp. Of them, the majority worked in an institute (10/30; 33.33%) and had "15 or more" years of experience (12/30; 40.00%). The null hypothesis was rejected for all items and demonstrated the content validity of each item. Similar results were found for the factors of the ESI. Finally, the total Aiken's V for the ESI did not include the values of the null hypothesis in the confidence intervals (V=0.78; CI95 [0.70; 0.85]), demonstrating content validity.

ESI-Sp is a valid and representative instrument to determine subjective experiences in patients with a high risk of schizophrenia. The construct validation of the ESI-Sp is pending, which our research group will carry out after this first step.