Discovering the hidden benefits of cognitive interviewing in two languages: The first phase of a validation study of the Integrated Palliative care Outcome Scale

Background: The Integrated Palliative care Outcome Scale is a newly developed advancement of the Palliative care Outcome Scale. It assesses patient-reported symptoms and other concerns. Cognitive interviewing is recommended for questionnaire refinement but not adopted widely in palliative care research.

Aim: To explore German- and English-speaking patients' views on the Integrated Palliative care Outcome Scale with a focus on comprehensibility and acceptability, and subsequently refine the questionnaire.

Methods: Bi-national (United Kingdom/Germany) cognitive interview study using 'think aloud' and verbal probing techniques. Interviews were audio-recorded, transcribed verbatim and analysed using thematic analysis and pre-defined categories. Results from both countries were collated and discussed. The Integrated Palliative care Outcome Scale was then refined by consensus.

Setting/participants: Purposely sampled patients from four palliative care teams in palliative care units, general hospital wards and in the community.

Results: A total of 15 German and 10 UK interviews were conducted. Overall, comprehension and acceptability of the Integrated Palliative care Outcome Scale were good. Identified difficulties comprised the following: (1) comprehension problems with specific terms (e.g. 'mouth problems') and length of answer options; (2) judgement difficulties, for example, due to the 3-day recall for questions; and (3) layout problems. Combining the results from both countries (e.g. regarding 'felt good about yourself') and discussing them from both languages' perspectives resulted in wider consideration of the items' meaning, enabling more detailed refinement.

Conclusion: Cognitive interviewing proved valuable to increase face and content validity of the questionnaire. The concurrent approach in two languages - to our knowledge the first such approach in palliative care - benefited the refinement. Psychometric validation of the refined Integrated Palliative care Outcome Scale is now underway.