PFO is used to frame research questions on prognosis in medicine and health.
Reference: Munn Z, Stern C, Aromataris E, Lockwood, C., & Jordan, Z. (2018). What kind of systematic review should I conduct? A proposed typology and guidance for systematic reviewers in the medical and health sciences. BMC Medical Research Methodology, 18, 5. doi: 10.1186/s12874-017-0468-4