The fourth subcategory of studies related to the level of experience of residents includes 43 studies comparing faculty to residents. Thirty-eight of these studies focused on surgical disciplines (aesthetic surgery, general surgery, thoracic surgery, orthopedics, urology, ophthalmology and obstetrics and gynecology) [
52‐
89]. The remaining five studies were conducted in radiology [
90,
91], family medicine [
92,
93] and anesthesiology [
94]. Thirty-one studies reported no statistically significant differences between faculty and residents on a wide variety of outcomes including mortality, morbidity and length of stay [
52,
54,
56‐
58,
61,
63,
67‐
69,
73‐
90,
92‐
94]. Although patient outcomes were similar, 12 of these 31 studies did report a significantly longer operation time for residents [
61,
67,
69,
74,
77,
78,
81,
83,
84,
87‐
89]. Nine studies reported negative outcomes of residents' involvement in patient care [
53,
55,
59,
60,
62,
65,
66,
71,
91]. Of these nine studies, five studies found significant differences between faculty and residents [
53,
55,
59,
60,
91]. Residents' cases resulted in a modestly elevated blood loss during surgery without clinical consequences [
53], radiographic or clinical leaks after esophagectomies without a higher take-back rate [
55], a small but significantly higher take-back rate after cardiac operations [
59], a discrepancy rate of 13.6% for residents' preliminary interpretations of radiology reports [
91], and higher morbidity rates and length of stay for patients cared for by residents working without supervision [
60]. Of the other four studies, two compared their outcomes to results in the literature [
62,
65], one did not formally train their residents [
71] and another study reported the negative impact of residents' assistance in laparoscopic gastric bypass surgery compared with fellow or attending level assistance [
66]. Three studies reported negative outcomes for faculty cases, likely caused by selection bias [
64,
70,
72].
Sixteen studies highlight the need for supervision by showing similar patient outcomes for supervised residents [
52,
54,
56‐
58,
68,
73,
75,
76,
79,
80,
85,
86,
90,
94] or worse patient outcomes for unsupervised residents [
60,
84]. Many studies compared faculty with residents in small settings with small sample sizes. However, two studies reported patient sample sizes > 5,000 patients with similar patient outcomes for both faculty and supervised residents after adjusting for case-mix [
56,
85].