Is There Selection Bias among Senior Medical
Students Who Choose to Participate in a
Surgery Internship Preparation Course?
EMILY W. ZANTOW, BSE, DOROTHY A. ANDRIOLE, MD,
DONNA B. JEFFE, PHD, JULIE WOODHOUSE, RN, L.
MICHAEL BRUNT, MD
WASHINGTON UNIVERSITY SCHOOL OF MEDICINE
ST. LOUIS, MO
Disclosures
 Emily W. Zantow – no disclosures
 L. Michael Brunt – no disclosures
Background
 Medical schools are increasingly offering surgery
internship preparation courses (SIPC) to senior
medical students planning to enter surgical
specialties
 SIPC are optional and may vary in student
participation level
 Characteristics of students who participate vs those
who do not have not been described
 In 2006 we initiated a senior skills
preparation course open to students
in any surgical specialty
 Students planning to enter a surgical
internship are invited via an email
announcement
 Enrollment on a first-come, first-
served basis
JACS 2008; 206:897-907.
SIPC Course Structure at WUSM
 3-hour sessions once per week
for 7 weeks

Curriculum includes:
Basic suturing and knot-tying
 Emergent procedural skills
 On call problems
 Energy devices and staplers
 Basic laparoscopic skills
 Animate lab
 Final assessment

SIPC Course Structure at WUSM
 Sessions consist of a short didactic followed by
hands-on instruction and practice
 Instruments and materials for independent practice
Hypothesis
 Students who participate in a SIPC might differ in
background or other areas of performance than
those who choose not to participate
Methods
 Database of individualized records was constructed
for all graduates in the 2006-2011 classes who
entered surgical residencies (IRB approval)

183 graduates total matched in surgical specialty

88 (48.1%) participated in the SIPC
Methods
 Independent associations between SIPC
participation and the following were explored:
First-attempt USMLE Step 1 score
 Third-year required clinical clerkships’ GPA
 3rd Year Surgical-skills score (self-reported, end of 3rd
year)
 Surgical specialty
 Gender

3rd Year Surgical-Skills Score
 Survey given at the end of the third year
 6 skills were analyzed:
 Peripheral IV placement (adult)
 Incision and drainage of a superficial
abscess
 Suture a superficial laceration
 Tie a two-handed knot
 Debride a superficial wound
 Orotracheal intubation (adult)
 Scored on a 1-5 scale: 1 = I have never been instructed in this; 5 = I
can do this independently
 Mean surgical-skills score calculated for the analysis
Methods
 Database was analyzed using ANOVA, chi-square
tests, and a logistic regression model
 p-values of < 0.05 were considered significant
Results
Mean GPA
Mean Step 1 Score
4
3.5
265
3.54
3.5
241.5
237.9
225
205
3
2.5
245
185
165
p = 0.171
2
145
p = 0.431
125
Participant
Non-participant
Participant
Non-participant
 In ANOVAs, participation was not associated with
Step 1 score or GPA
Results
Mean Surgical-Skills Score
4.25
4.2
4.15
4.1
4.05
4
3.95
3.9
3.85
4.2
p = 0.017
3.97
Participant
Non-participant
 SIPC participation was associated with higher mean
3rd year surgical-skills score
Results
Surgical Specialty
100
90
80
56
60
40
20
Participant
32
Non-participant
5
p < 0.001
0
General Surgery
Other Surgical Specialties
 In chi-square tests, SIPC participation was associated
with surgery specialty choice
Results
Surgical Specialty
100
90
80
56
60
Participant
40
32
20
86%
38%
5
p < 0.001
0
General Surgery
Non-participant
Other Surgical Specialties
 In chi-square tests, SIPC participation was associated
with surgery specialty choice
Results
Gender
60
50
50
55
38
40
40
30
Participant
20
Non-participant
10
p = 0.883
0
Male
Female
 Participation was not associated with gender
Results
 In the logistic regression model, independent
predictors of SIPC participation included:

Higher surgical-skills score
[aOR] = 1.80
 95% CI = 1.05-3.07
 p = 0.032


General surgery specialty choice
[aOR] = 11.00
 95% CI = 3.89-31.15
 p < 0.001

Summary
 SIPC participants comprised a higher-performing
group on the basis of self-assessed surgical-skills
scores
 SIPC participants consisted of a greater percentage
of students entering general surgery, indicating some
selection bias among participants
 No differences were seen on other objective pre-4th
year performance measures
Conclusion
 Our results have implications for whether SIPCs
should be offered as optional or required courses and
for the design of evaluations of the impact of SIPC
participation on surgical-intern preparedness