Below is an instruction from Human. Write a response.
    ### Instruction:
    How to diagnose Prader-Willi syndrome ?
    ### Response:
    How is Prader-Willi syndrome diagnosed? There are clinical diagnostic criteria for Prader-Willi syndrome (PWS) that were developed in the past that continue to be useful. These criteria can be viewed on the National Institute of Health's NICHD Web site. However, the current mainstay of a diagnosis when PWS is suspected is a form of genetic testing called DNA methylation testing.
    