Can I combine results from different modes of administration?
In some cases, data may be collected using different approaches within the same study. Three situations are not uncommon:
Regarding the equivalence of proxy and patient responses, research to date suggests that responses should probably not be directly aggregated, at least without further within-study analysis of responses patterns. Hounsome et al (2011) found that proxy versions had good reliability and validity for use in dementia patients but highlighted that it was important to select appropriate proxies and that different proxies (e.g., family carers, institutional carers, and health-care professionals) provide different ratings for patients’ health. They also noted that there was a lack of association between patient and proxy ratings. In a review of the use of EQ-5D in stroke patients, Oczkowski et al (2010) found that most studies reported that proxy respondents overestimated impairments compared with patient self-reports. Gabbe et al (2012) found that, in trauma patients 12 months after injury, agreement between patient and proxy respondents was substantial for the mobility and self-care items and moderate for the remaining 3 dimensions.Based on these considerations, in the case of a) and c), we recommend that when different modes of administration are used, a variable indicating mode of administration should be recorded in the data set. Data should always be analysed separately before aggregating, and researchers should report consent rates, data completeness and other potential sources of bias for the different modes of administration.Muehlhausen W et al. Equivalence of electronic and paper administration of patient-reported outcome measures: a systematic review and meta-analysis of studies conducted between 2007 and 2013. Health Qual Life Outcomes 2015;13:167.