Content validity of the illness perceptions questionnaire--revised among people with type 2 diabetes: a think-aloud study

Objectives: To access the cognitions of adults with type 2 diabetes whilst completing items on the Illness Perceptions Questionnaire – Revised (IPQ-R). To determine whether these cognitions are congruent with the meaning of items and subscales as interpreted by researchers and clinicians using the IPQ-R and to identify the nature and extent of problems that individuals experience when completing the IPQ-R.Design: Participants (n=36) were recruited from a primary care diabetes clinic and a hospital diabetes clinic. They were asked to complete the IPQ-R using a ‘think-aloud’ methodology.Main Outcome Measures: Transcripts were analysed to identify instances where participants expressed problems with item completion, or where there was inconsistency between verbal and written responses.Results: The most problematic subscales were those of ‘personal control’ and ‘consequences’. Conclusion: Generally, participants found the IPQ-R unproblematic. However, participants had problems with the concept of ‘cure’ and ‘symptoms’ in the context of type 2 diabetes, and with the negative phrasing used in some items. These findings have important implications for the interpretation of IPQ-R scores, particularly when the IPQ-R is used as the basis for individualised interventions among people with type 2 diabetes.