Well, a subjective test, in a quiet room, with test tones for references is satisfactory for most purposes - if the system determines that it is unable to assess the situation, it can be escalated to an MD.
And there is more that is taken in to account when setting the hearing aids, such as: Age Speech comprehension issues Loudness thresholds cognitive issues
As well there are a handfull of "red flags" that are looked for, some of which can only be done with a visual examination, and others by more involved audiometric testing.