Although hyperphagia (excessive appetite) is a hallmark of PWS, it's one of the most difficult features to accurately measure and characterize. Currently, the main tools in this area are questionnaires about food behavior and food interest. These can be answered by caregivers, or by the person with PWS. Although tremendously valuable, these measures are subjective, meaning they're influenced by the perception and opinion of the person filling them out.
To complement the information from these questionnaires, researchers are also working to develop objective biomarkers of food interest and hyperphagia in PWS. An objective biomarker is a reproducible and accurate measure, indicator or proxy.