Anthropometric outcomes, such as body weight, should be classified as General outcomes rather than Metabolism or nutrition outcomes. However, outcomes relating to weight may instead (or also be) a measure of impact (in other words, relating to one or more of the functioning domains). Further information may be required (for example, in terms of the measurement tool or exact wording of the questions) to determine whether the outcome relates to the physiological symptom or the impact of that symptom. For example, outcomes such as "diarrhoea" and "malabsorption" may relate to both/either Gastrointestinal and/or Physical functioning, depending on context.
Outcomes such as sleep may also be classified as either physiological or functioning, depending on focus. For example, outcomes relating to the impact of sleep deprivation would be classified within the relevant functioning domain:
"Physical exhaustion due to sleep deprivation" would be classified within Physical functioning.
"Impact of sleep deprivation on ability to work" would be classified within Role functioning.
"Impact of sleep deprivation on ability to socialise" would be classified within Social functioning.
"Inability to cope due to sleep deprivation" would be classified within Emotional functioning.
"Inability to concentrate due to sleep deprivation" would be classified within Cognitive functioning.
In contrast (and probably more commonly), sleep outcomes which relate to clinical signs, symptoms, lab measures, etc. would be classified under the relevant physiological domain, according to the MedDRA hierarchy. We would therefore recommend that researchers use a combination of their clinical knowledge and guidance by MedDRA to classify physiological sleep outcomes into the appropriate domain.
When in doubt, we would recommend classifying outcomes in all potentially relevant domains (for example, functioning and/or any of the potentially relevant physiological domains).
Note that the classification of outcomes does not depend on who (e.g. clinician versus patient) is recording the outcome: for example, a patient-reported measure of "response to treatment" would still be considered a physiological outcome, unless it was defined specifically in terms of impacting the patient’s life.