The development and validation of the Diagnosis Impact Scale (DIS)

: a self-report measure of the effect of psychiatric diagnoses on recipients

Abstract

Background: Despite the dominance of psychiatric diagnosis within mental healthcare systems, there is no validated measure of diagnosis impact on those who receive them. Consequently, there is also a paucity of statistically generalisable research on the experience of receiving and living with a diagnosis.
Aims: To develop a valid and reliable measure of the effect of psychiatric diagnosis on recipients, the Diagnosis Impact Scale (DIS), for clinical and research use. 
Method: Measure development protocols used included the generation of an item pool, expert rating of items, and Three Step Test Interviews. Psychometric properties of the DIS were investigated, including internal consistency, convergent validity, discriminant validity, and criterion validity. A principal components analysis was carried out on a sample of 248 people with psychiatric diagnoses, followed by a two-parameter IRT analysis.
Findings: The principal components analysis suggested that the 19-item DIS had two discrete subscales: Helpfulness of Diagnosis and Diagnosis-Related Self-Stigma. Each displayed excellent reliability in this sample, with Cronbach’s alphas of 0.93 (n=256) and 0.81 (n=263) for Helpfulness of Diagnosis and Diagnosis-Related Self-Stigma respectively. They were also found to have acceptable content and construct validity. Significant associations were found between both subscales and diagnosis type, perceived correct diagnosis, receipt of treatment due to diagnosis, and helpfulness of said treatment. Helpfulness of Diagnosis was significantly associated with age and time since diagnosis. Diagnosis-Related Self-Stigma was significantly associated with having multiple diagnoses, the number of these, and the type of healthcare professional who gave the diagnosis (e.g. GP or psychiatrist). The two-parameter IRT analysis showed that both subscales were within acceptable ranges for discrimination and differentiationbetween strength of attitude.

Date of Award	11 Dec 2020
Original language	English
Awarding Institution	University of Roehampton
Supervisor	Mick Cooper (Supervisor) & Gina Pauli-Jones (Supervisor)