Table 6. Quality Assessment of Selected Observational Studies on Non-ED Interventions to Reduce ED Utilization Using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Criteria.

Possible limits of observational studies Failure to develop and apply appropriate eligibility criteria (inclusion of control population) Flawed measurement of both exposure and outcome Failure to control confounders and to measure all known prognostic factors Imprecision of outcomes (i.e., wide CIs) Incomplete follow-up
First Author (Reference)	Existing Limitations	Overall Quality of Evidence
Patient education
Glavan (10)	1, 3, 4	Very low
McWilliams (11)	1, 3	Very low
Schonlau (13)	1, 3	Very low
Non-ED capacity increase
Chalder (22)	1, 2, 3	Very low
Hsu (24)	1, 3, 4	Very low
Hudec (15)	1, 3, 4	Very low
O'Kelly (16)	1, 2, 3, 4	Very low
Philips (23)	1, 2, 3	Very low
Rust (19)	1, 2, 3	Very low
Solberg (20)	1,2,3	Very low
Solberg (21)	1,2,3,4	Very low
van Uden (17)	1, 2, 3	Very low
Wang (18)	2, 3	Very low
Prehospital diversion
Schaefer (25)	1, 3, 5	Very low
Managed care
Badgett (27)	1, 3, 4	Very low
Catalano (28)	1, 3	Very low
Catalano (29)	1,3, 4	Very low
Dickey (30)	1, 3, 4	Very low
Franco (31)	1, 2, 3	Very low
Glazier (32)	1, 3	Very low
Hurley (33)	1, 2, 3, 4	Very low
Josephson (34)	1,3, 4	Very low
Murphy (35)	1, 3	Very low
Piehl (36)	3, 4	Very low
Price (37)	2, 4	Very low
Patient financial incentives
Hsu (39)	3	Very low
Lowe (47)	1, 2, 3	Very low
Lowe (40)	2, 3	Very low
Mortensen (48)	1, 2, 3, 5	Very low
Selby (42)	3	Very low
Wallace (43)	3	Very low
Waters (45)	2, 3,4	Very low
Wharam (44)	1,3,5	Very low
Wilson (46)	2, 3	Very low