 Despite their plausibility, these tests are not methodologically innocuous. Content validity, for instance, is assessed on the basis of qualitative research in the form of patient interviews, focus groups, and qualitative cognitive interviewing (the latter refers to a method that asks respondents to think aloud and describe their thought processes as they answer the instrument questions and involves follow-up questions in a field test interview to gain a better understanding of how patients interpret questions). This qualitative research aims to develop questions with standardized meanings that are shared between patients and clinicians. Arguably, however, there will always be differences in interpreting phrases such as “bodily pain” or “difficulty in lifting one”s arm’ because they refer to a patient’s experiences, and these will differ from patient to patient and, in a given patient, from time to time (Rapkin and Schwartz 2004). Moreover, there may be good philosophical reasons to allow for the expression of a sufficient array of legitimate perspectives on health and quality of life instead of insisting on a standardization of meaning across patients and contexts (McClimans 2010). Similarly, internal consistency can be desirable only to the extent that the concept is a relatively simple one and different questions really do address the same concept. It is of less relevance when the disorder is heterogeneous (McClimans and Browne 2011). These kinds of worries can be raised with respect to each of the measurement tests. Finally, there is an issue when several PROMs that address a given disorder or treatment exist. Different PROMs will score differently with respect to the different tests, and there is no universally valid schema to weigh their relative importance (ibid.).