Table 1. Search strategy for identifying studies that align with our four topics: 21st Century Cures Act, COVID-19, disparities in portal adoption and use, and proxy access to portals.

Topic	PubMed search strategy	Other identified	Search results
21st Century Cures Act	• Title and abstract  • Search limited: 2020–2022  • Search string: (((“patient portal”) OR (“personal health record”)) AND ((“opennotes”) OR (“open notes”) OR (“open result”) OR (“open results”) OR (“21st century cures act”)))	2	• Total number of results: 26  • Total included: 18
COVID-19	• All fields  • Search limited: 2020–2022  • Search string: (((“patient portal”) OR (“personal health record”)) AND (“covid”))	0	• Total number of results: 55  • Total included: 28
Disparities in adoption and use	• All fields  • Search limited: 2020–2022  • Search string: (((“patient portal”) OR (“personal health record”)) AND ((“healthcare disparities”) OR (“health care disparities”) OR (“health disparities”) OR (“health equity”)))	2	• Total number of results: 27  • Total included: 12
Proxy access	• All fields  • Search limited: 2017–2022  • Search string: (((patient portal) OR (personal health record)) AND (“proxy”))	1	• Total number of results: 78  • Total included: 16