"Angaben" needs to be read here as "answers" (by the patient to the test questions).
cf. Wikipedia:
Social desirability bias is a social science research term that describes the tendency of survey respondents to answer questions in a manner that will be viewed favorably by others. It can take the form of over-reporting "good behavior" or under-reporting "bad", or undesirable behavior. The tendency poses a serious problem with conducting research with self-reports, especially questionnaires. This bias interferes with the interpretation of average tendencies as well as individual differences.
https://en.wikipedia.org/wiki/Social_desirability_bias