The Use of Single-Item Ratings Versus Traditional Multiple-Item Questionnaires to Assess Mood and Health.

Collecting real-world evidence via 'at home' assessments in ambulatory patients or healthy volunteers is becoming increasingly important, both for research purposes and in clinical practice. However, given the mobile technology that is frequently used for these assessments, concise assessments are preferred. The current study compared single-item ratings with multiple-item subscale scores of the same construct, by calculating the corresponding Bland and Altman 95% limits of agreement interval. The analysis showed that single-item ratings are usually in good agreement with assessments of their corresponding subscale. In the case of more complex multimodal constructs, single-item assessments were much less often in agreement with multiple-item questionnaire outcomes. The use of single-item assessments is advocated as they more often incorporate assessments of all aspects of a certain construct (including the presence, severity, and impact of the construct under investigation) compared to composite symptom scores.