Is There Selection Bias among Senior Medical
Students Who Choose to Participate in a
Surgery Internship Preparation Course?
E M I L Y W . Z A N T O W , B S E , D O R O T H Y A . A N D R I O L E , M D ,
D O N N A B . J E F F E , P H D , J U L I E W O O D H O U S E , R N , L .
M I C H A E L B R U N T , M D
W A S H I N G T O N U N I V E R S I T Y S C H O O L O F M E D I C I N E
S T . L O U I S , M O

 Emily W. Zantow – no disclosures
 L. Michael Brunt – no disclosures

 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, firstserved basis
JACS 2008; 206:897-907.

 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

 Sessions consist of a short didactic followed by hands-on instruction and practice
 Instruments and materials for independent practice

 Students who participate in a SIPC might differ in background or other areas of performance than those who choose not to participate

 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

 Independent associations between SIPC participation and the following were explored:

First-attempt USMLE Step 1 score

Third-year required clinical clerkships’ GPA

3 rd Year Surgical-skills score (self-reported, end of 3 rd year)

Surgical specialty

Gender

rd
 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

 Database was analyzed using ANOVA, chi-square tests, and a logistic regression model
 p-values of < 0.05 were considered significant

4
3,5
3
2,5
2
Mean GPA
3,5 3,54 p = 0.171
Participant Non-participant
265
245
225
205
185
165
145
125
Mean Step 1 Score
237,9
241,5 p = 0.431
Participant Non-participant
 In ANOVAs, participation was not associated with
Step 1 score or GPA

4,25
4,2
4,15
4,1
4,05
4
3,95
3,9
3,85
Mean Surgical-Skills Score
4,2
3,97 p = 0.017
Participant Non-participant
 SIPC participation was associated with higher mean
3 rd year surgical-skills score

100
80
60
40
20
0
32
5
General Surgery
Surgical Specialty
90
56
Participant
Non-participant p < 0.001
Other Surgical Specialties
 In chi-square tests, SIPC participation was associated with surgery specialty choice

100
80
60
40
20
0
32
86%
5
General Surgery
Surgical Specialty
90
56
38%
Participant
Non-participant p < 0.001
Other Surgical Specialties
 In chi-square tests, SIPC participation was associated with surgery specialty choice

Gender
60
50
40
30
20
10
0
50
55
38
40
Participant
Non-participant p = 0.883
Male Female
 Participation was not associated with gender

 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

 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

 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