Table 1.

Summary of quantitative umbrella review findings and Grading of Strength of Evidence for Quantitative Research at the Level of an Umbrella Review evaluation of quantitative evidence.

Umbrella review domain and summary of quantitative findings statement (SRa source)		Strength of the evidence according to the GRADE-URb criteriac
Patient characteristics
	Patients with better controlled diabetes are more likely to enroll or use a portal as compared to other patients with diabetes [14,31,35].	Moderate
	Patients with private insurance in the US context are more likely to enroll or use a portal [14,15,31,34,35].	Moderate
	Patients with higher illness(es) burden or need are more likely to enroll or use a portal [14,15,31,34].	Moderate
	White people are more likely to enroll or use a portal [14,15,31,32,34].	Moderate
	Middle-aged people (≤65 years) are more likely to enroll or use a portal [14,17,31,32,34].	Moderate
	People who have a higher income are more likely to enroll or use a portal [14,15,31,35].	Moderate
	Males with diabetes are more likely to enroll or use portal as compared with females with diabetes [14,35].	Moderate
	Patients with higher health literacy are more likely to enroll or use a portal [14,17,30].	Low
	Females are more likely to access online information and use a portal [17,31,34].	Low
	People who have a higher education level are more likely to enroll in and use a patient portal [14,31,35].	Low
Patient-related facilitators
	Patients are more likely to register and use a portal after portal-related education and training [32].	Moderate
Patient satisfaction
	Patients who use patient portals report higher satisfaction with communication, treatment, medications, and care [16,31,34,35].	Moderate
Behavioral effects
	Use of patient portals can increase adherence, mostly medication adherence across different patient populations [16,17,31,33,34].	Moderate
	Use of patient portals can improve screening, vaccinations, examinations, and/or care across different patient populations [31,34,35].	Moderate
	Use of patient portals can improve visit preparation and communication and information sharing between patients and providers [14,16,31,34].	Low
Service utilization effects
	Health care provider’s workload related to contacts and messaging does not change with patient portal adoption [34].	Moderate
	Patients’ access to social support and mental health and testing services does not change with portal use [31,33].	Moderate
	Hospitalization rates do not change with patient portal use [16,31,34].	Low
	Emergency department visits do not change with patient portal use [16,31,34].	Low
	Phone or messaging volume received by health care providers does not change with patient portal use [16,17,31,34].	Low
	Patient portal use results in an increase in office, primary care, specialist, outpatient, or after-hour visits [15-17,31,34,35].	Low
	Patient portal use does not reduce no-show rates [17,34].	Low
Clinical outcomes
	There is improvement in HbA1cd levels for patients with diabetes who use patient portals [15-17,31].	Moderate
	There is improvement in LDLe, HDLf, cholesterol, or lipids for patients with diabetes who use patient portals [15,16,31,35].	Low
	There is no change in systolic and diastolic blood pressure for patients with diabetes or hypertension who use patient portals [16,31,35].	Low
	Psychosocial, cognitive function, BMI, symptom stability, and depression and anxiety status does not change across multiple patient populations who use patient portals [16,17,31].	Low
Patient-oriented outcomes
	Patient empowerment and self-efficacy scores do not change with portal use [16,31].	Low

^aSR: systematic review.

^bGRADE-UR: Grading of Recommendations, Assessment, Development, and Evaluations at the Level of an Umbrella Review.

^cIndicates the strength of the evidence and was calculated based on study limitations, directness, consistency, precision, and reporting of bias. The ratings are from high, moderate, and low. Any statements we evaluated as insufficient were moved to the supporting evidence tables in Multimedia Appendix 4.

^dHbA_1c: hemoglobin A_1c.

^eLDL: low-density lipoprotein.

^fHDL: high-density lipoprotein.