Patient understanding of two commonly used patient reported outcome measures for primary care: a cognitive interview study

Mairead Murphy, Sandra Hollinghurst, Chris Salisbury

Standardised generic patient-reported outcome measures (PROMs) which measure health status are often unresponsive to change in primary care. Alternative formats, which have been used to increase responsiveness, include individualised PROMs (in which respondents specify the outcomes of interest in their own words) and transitional PROMs (in which respondents directly rate change over a period). The objective of this study was to test qualitatively, through cognitive interviews, two PROMs, one using each respective format. The individualised PROM selected was the Measure Yourself Medical Outcomes Profile (MYMOP). The transitional PROM was the Patient Enablement Instrument (PEI). Twenty patients who had recently attended the GP were interviewed while completing the questionnaires. Interview data was analysed using a modification of Tourangeau's model of cognitive processing: comprehension, response, recall and face validity. Patients found the PEI simple to complete, but for some it lacked face validity. The transitional scale was sometimes confused with a status scale and was problematic in situations when the relevant GP appointment was part of a longer episode of care. Some patients reported a high enablement score despite verbally reporting low enablement but high regard for their GP, which suggested hypothesis-guessing. The interpretation of the PEI items was inconsistent between patients. MYMOP was more difficult for patients to complete, but had greater face validity than the PEI. The scale used was open to response-shift: some patients suggested they would recalibrate their definition of the scale endpoints as their illness and expectations changed. The study provides information for both users of PEI/MYMOP and developers of individualised and transitional questionnaires. Users should heed the recommendation that MYMOP should be interview-administered, and this is likely to apply to other individualised scales. The PEI is open to hypothesis-guessing and may lack face-validity for a longer episode of care (e.g. in patients with chronic conditions). Developers should be cognisant that transitional scales can be inconsistently completed: some patients forget during completion that they are measuring change from baseline. Although generic questionnaires require the content to be more general than do disease-specific questionnaires, developers should avoid questions which allow broad and varied interpretations.