First Aid Q&A for the USMLE Step 1, 3e.PDF

FIRST AID

™

Q&A FOR THE
USMLE
STEP 1
Second Edition
SENIOR EDITORS

EDITORS

Tao Le, MD, MHS

Karen A. Adler, MD

Assistant Clinical Professor
Chief, Section of Allergy and Clinical Immunology
Department of Medicine
University of Louisville

Resident
Department of Psychiatry
Massachusetts General Hospital

Seth K. Bechis, MS

Yale School of Medicine
Class of 2012

University of California, San Francisco
Class of 2010

Jacob S. Appelbaum
Carina H.G. Baird, MD
Resident
Department of Pediatrics
University of California, San Francisco

Xuemei Cai
Harvard Medical School
Class of 2009

Phillip J. Gray, Jr.
Johns Hopkins University School of Medicine
Class of 2009

Christopher R. Kinsella, Jr.
Drexel University College of Medicine
Class of 2009

Gabriel J. Martinez-Diaz
Stanford University School of Medicine
Class 2010

New York / Chicago / San Francisco / Lisbon / London / Madrid / Mexico City
Milan / New Delhi / San Juan / Seoul / Singapore / Sydney / Toronto


Copyright © 2009 by Tao Le. All rights reserved. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or

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D E D I C AT I O N
To the contributors to this and future editions, who took time to share their
knowledge, insight, and humor for the benefit of students, residents, and
clinicians.
and
To our families, friends, and loved ones, who supported us in the task of
assembling this guide.


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CONTENTS

Authors

vii

Associate Authors

ix

Faculty Reviewers

x

Preface

xiii

Acknowledgments

xv

How to Contribute

xvii

S EC T IO N I

G E N E RAL PRI NC I PLES

1

Chapter 1

Behavioral Science

Chapter 2

Biochemistry

17

Chapter 3

Embryology

49

Chapter 4

Microbiology

63

Chapter 5

Immunology

91

Chapter 6

Pathology

111

Chapter 7

Pharmacology

127

S EC T IO N I I

O R G A N SYST E M S

3

14 3

Chapter 8

Cardiovascular

145

Chapter 9

Endocrine

179

Chapter 10

Gastrointestinal

213

Chapter 11

Hematology-Oncology

247

Chapter 12

Musculoskeletal and Connective Tissue

279

Chapter 13

Neurology

309

Chapter 14

Psychiatry

331

Chapter 15

Renal

347

Chapter 16

Reproductive

381

Chapter 17

Respiratory

413

v


S EC T IO N I I I

F U LL-LE N G T H E X A M I NAT I O N S

445

Test Block 1

447

Test Block 2

481

Test Block 3

513

Test Block 4

547

Test Block 5

581

Test Block 6

613

Test Block 7

645

Appendix: Common Laboratory Values

675

About the Authors

681

vi


AUTHORS
REBECCA AHRENS

SHARIFEH (SHERI) FARASAT

Tri-Institutional MD/PhD Program
Weill Medical College of Cornell University

Johns Hopkins University School of Medicine
Class of 2009

SARA ALCORN

JAMES A. FEINSTEIN, MD

Harvard Medical School
Class of 2010

Resident
Department of Pediatrics
Seattle Children's Hospital and Regional Medical Center

VIJAY BABU, MD
Intern
Department of Internal Medicine
The Reading Hospital
Reading, Pa.

PAULA BORGES, MS
Stanford University Medical School
Class of 2009

RACHEL BORTNICK, MPhil
Medical Scientist Training Program, Year V
Harvard Medical School

STEVEN CHEN
Johns Hopkins University School of Medicine

Class of 2010

JOHN CHILDRESS III
University of Michigan Medical School
Class of 2010

RAGHU CHIVUKULA
Medical Scientist Training Program, Year IV
Johns Hopkins University School of Medicine

JUSTIN BRENT COHEN
Yale School of Medicine
Class of 2009

ANA COSTA, MD
Resident
Department of Anesthesiology
Weill Medical College of Cornell University

SHENNEN FLOY
Harvard Medical School
Class of 2009

ARIELLA FRIEDMAN
Weill Medical College of Cornell University
Class of 2008

ROBERT J. GIANOTTI, MD
Resident
Department of Internal Medicine

New York University

PHILIP HALL
Yale School of Medicine
Class of 2010

DANIEL M. HALPERIN
Weill Medical College of Cornell University
Class of 2009

COLLEEN M. HARRISON
Harvard Medical School
Class of 2009

CHLOE HILL
Weill Medical College of Cornell University
Class of 2010

SELENA LIAO
Harvard Medical School
Class of 2009

ANDRES E. CRUZ-INIGO

KEN LIN

Weill Medical College of Cornell University

MARTIN H. DOMINGUEZ

Medical Scientist Training Program, Year V
Harvard Medical School
Class of 2010

MD/PhD Program
Yale School of Medicine

SUSAN MATHAI

ALLEN OMID EGHRARI

Yale School of Medicine
Class of 2009

Johns Hopkins University School of Medicine
Class of 2009

vii


HEATHER MCGEE, MPhil

TOMEKA L. SUBER

Medical Scientist Training Program, Year IV
Yale School of Medicine

Medical Scientist Training Program
Johns Hopkins University School of Medicine

LEAH MCNALLY

CARLOS A. TORRE

Yale School of Medicine
Class of 2009

University of Puerto Rico, Medical Science Campus
Class of 2009

EMILY PFEIL

JONATHAN TZU

Johns Hopkins University School of Medicine
Class of 2009

Johns Hopkins University School of Medicine
Class of 2009

MICHELLE RIOS, MD

BRANT W. ULLERY, MD

Resident
Department of Internal Medicine
University of California, Los Angeles Medical Center

Resident
Department of General Surgery

Hospital of the University of Pennsylvania

MAYA ROBERTS

KELLY VRANAS, MD

Yale School of Medicine and Harvard School of Public Health
Class of 2009

Resident
Department of Internal Medicine
Hospital of the University of Pennsylvania

MARIANELI RODRIGUEZ
Medical Scientist Training Program
Johns Hopkins University School of Medicine

SEPIDEH SABER
Stanford University School of Medicine
Class of 2010

BENJAMIN SMITH
Harvard Medical School
Class of 2010

SARA STERN-NEZER
Stanford University School of Medicine and
University of California, Berkeley School of Public Health

viiiviii

FREDERICK WANG
Yale School of Medicine
Class of 2010

MARC WEIN
Medical Scientist Training Program, Year VI
Harvard Medical School

RASIKA WICKRAMASINGHE, PhD
Medical Scientist Training Program, Year VI
Johns Hopkins University School of Medicine


ASSOCIATE AUTHORS
JAN BROWN II

BENJAMIN SILVERBERG, MS

St. George’s University School of Medicine
Class of 2010

University of Connecticut School of Medicine
Class of 2009

PAUL D. DI CAPUA

HARRAS ZAID

Yale School of Medicine

Class of 2009

University of California, San Francisco School of Medicine
Class of 2010

LARS GRIMM
Yale School of Medicine
Class of 2009

NICOLE M. HSU
Second Lieutenant, United States Air Force Medical Service Corps
F. Edward Hébert School of Medicine
Uniformed Services University of the Health Sciences
Class of 2009

ix


FACULTY REVIEWERS
R. SHARON CHINTHRAJAH, MD

JOHN R. MCARDLE, MD

Chief Resident
Department of Internal Medicine
California Pacific Medical Center
San Francisco, Calif.

Assistant Professor of Medicine
Section of Pulmonary & Critical Care Medicine

Yale School of Medicine

RACHEL CHONG, MD, PhD

ANDREW MILLER, DO

Endocrinologist
Lakeridge Health Corporation
Ontario, Canada

Fellow
Division of Rheumatology & Immunology
Department of Medicine
Vanderbilt University Medical Center

RONALD D. COHN, MD

TRACEY A. MILLIGAN, MD, MS

Assistant Professor, Pediatrics and Neurology
McKusick-Nathans Institute of Genetic Medicine
Director, Medical Genetics Residency Program
Director, Johns Hopkins University Center for Hypotonia
Johns Hopkins University School of Medicine

Associate Neurologist
Brigham and Women’s Hospital
Instructor in Neurology
Harvard Medical School

ALEXIS DANG, MD
Resident
Department of Orthopedic Surgery
University of California, San Francisco

GWENDOLYN J. GODFREY, DO, MPH
Resident
Department of Pathology and Laboratory Medicine
University of Louisville School of Medicine

MICHAEL J. PARKER, MD
Assistant Professor of Medicine
Division of Pulmonary and Critical Care Medicine
Beth Israel Deaconess Medical Center
Senior Interactive Media Architect
Center for Educational Technology
Harvard Medical School

MICHAEL S. RAFII, MD, PhD

KURT E. JOHNSON, PhD

Assistant Professor
Department of Neurosciences
University of California, San Diego School of Medicine

Professor of Anatomy and Regenerative Biology
The George Washington University School of Medicine

GEORGE A. SAGI, MD

New York-Presbyterian Hospital

WILLIAM KONIGSBERG, MD
Professor
Department of Molecular Biophysics and Biochemistry
Yale University School of Medicine

NABIL KOTBI, MD
Assistant Professor of Psychiatry
Weill Medical College of Cornell University
New York-Presbyterian Hospital

NAHLA A. MAHGOUB, MD
Instructor
Department of Psychiatry
Weill Medical College of Cornell University

xxx

LAWRENCE SIEGEL, MD, MPH
Instructor
Division of International Medicine & Infectious Diseases
Department of Medicine
Weill Medical College of Cornell University

RICHARD S. STEIN, MD
Professor
Department of Medicine
Vanderbilt University School of Medicine

JANIS M. STOLL, MD

EUNICE S. WANG, MD

Resident
Departments of Internal Medicine and Pediatrics
The University of Chicago Hospitals

Assistant Professor
Leukemia Service, Department of Medicine
State University of New York at Stony Brook School of Medicine
Roswell Park Cancer Institute
Buffalo, N.Y.

ANTHONY STURZU, MD
Fellow
Division of Cardiology
Massachusetts General Hospital
Harvard Medical School

EDWARD TANNER, MD
Chief Resident
Department of Gynecology and Obstetrics
Johns Hopkins University School of Medicine

SCOTT WEISENBERG
Weill Medical College of Cornell University

MICHAEL WEST, MD, PhD

Departments of Endocrinology and Metabolism
Department of Medicine
Johns Hopkins University School of Medicine

MUTHUKUMAR THANGAMANI, MD
Resident
Division of Nephrology
Department of Medicine
Weill Medical College of Cornell University

xi


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PREFACE

With the second edition of First Aid Q&A for the USMLE Step 1, we continue
our commitment to providing students with the most useful and upto-date preparation guides for the USMLE Step 1. This new edition represents
an outstanding effort by a talented group of authors and includes the following:
Ⅲ
Ⅲ
Ⅲ
Ⅲ
Ⅲ
Ⅲ

Almost 1000 high-yield USMLE-style questions based on the top-rated
USMLERx Qmax Step 1 Test Bank (www.usmlerx.com).

Concise yet complete explanations to correct and incorrect answers
Questions organized by general principles and organ systems
Seven full-length test blocks simulate the actual exam experience
High-yield images, diagrams, and tables complement the questions and
answers
Organized as a perfect complement to First Aid for the USMLE Step 1

We invite you to share your thoughts and ideas to help us improve First Aid
Q&A for the USMLE Step 1. See How to Contribute, p. xvii.
Louisville
San Francisco

Tao Le
Seth K. Bechis

xiiixiii
xiii


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ACKNOWLEDGMENTS

This has been a collaborative project from the start. We gratefully acknowledge the thoughtful comments and advice of the medical students, international medical graduates, and faculty who have supported the authors in the
continuing development of First Aid Q&A for the USMLE Step 1.
Additional thanks to the following for reviewing manuscript: Rachel Glaser,
MD; Niccolò Della Penna, MD; and Nathan Stitzel, MD.
For support and encouragement throughout the project, we are grateful to
Thao Pham, Louise Petersen, Selina Franklin, Jonathan Kirsch, and Vikas

Bhushan. Thanks to our publisher, McGraw-Hill, for the valuable assistance
of their staff. For enthusiasm, support, and commitment to this challenging
project, thanks to our editor, Catherine Johnson. For outstanding editorial
work, we thank Steve Freedkin, Isabel Nogueira, Mike Shelton, and Emma
D. Underdown. A special thanks to Rainbow Graphics for remarkable production work.
For contributions, correction, and surveys we thank Utkarsh Acharya, Achal
Achrol, Mohamad Alsabbagh, Mahyar Badrei, Judith Bellamy, Fernando Bolaños, Mohit Chaudhary, Alice Ching, Elizabeth Chisholm, Jenny ChuaTuan, Horacio Contreras, Navid Eghbalieh, Felix Geissler, George Ghobrial,
Aaron Goldsmith, Ruben Gonzalez, Leo Han, Scott Herd, Alex Hunter, Atul
Jain, Katherine Kline, Michael R. Krainock, Ella Leung, Kelvin Li, Milay
Luis, Elizabeth Lynn, Adrienne Ma, Eiyu Matsumoto, Francois Merle, Andrew Nakamoto, Jessica Newbury, Jacqueline Ng, Stephanie Nguyen, Ismari
Ortiz, Puneet Panda, Gia Patel, Charles Pearlman, Laura Petrillo, Jason L.
Pirga, Jessica Rabbitt, Joseph Richards, Oliver Rothschild, Abhit Singh, Stephen Squires, Hugo Torres y Torres, Jennifer Turley, Ben Watters, Ben Weinberg, Jed Wolpaw, Vincent Yang, and Jun Yin.
Louisville
San Francisco

Tao Le
Seth K. Bechis

xv


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HOW TO CONTRIBUTE

This edition of First Aid Q&A for the USMLE Step 1 incorporates hundreds of contributions and
changes suggested by faculty and student reviewers. We invite you to participate in this process. We also
offer paid internships in medical education and publishing ranging from three months to one year (see
next page for details). Please send us your suggestions for

Ⅲ
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Corrections or enhancements to existing questions and explanations
New high-yield questions
Low-yield questions to remove

For each entry incorporated into the next edition, you will receive a $10 gift certificate, as well as personal acknowledgment in the next edition. Diagrams, tables, partial entries, updates, corrections, and
study hints are also appreciated, and significant contributions will be compensated at the discretion of
the authors.
The preferred way to submit entries, suggestions, or corrections is via our blog:
www.firstaidteam.com
Otherwise, please send entries, neatly written or typed or on disk (Microsoft Word), to:
First Aid Q&A for the USMLE Step 1, Second Edition
914 North Dixie Avenue, Suite 100
Elizabethtown, KY 42701
All entries become property of the authors and are subject to editing and reviewing. Please verify all data
and spellings carefully. In the event that similar or duplicate entries are received, only the first entry received will be used. Include a reference to a standard textbook to facilitate verification of the fact. Please
follow the style, punctuation, and format of this edition if possible.

I N T E R N S H I P O P P O RT U N I T I E S

The First Aid Team is pleased to offer part-time and full-time paid internships in medical education and
publishing to motivated medical students and physicians. Internships may range from three months (e.g.,
a summer) up to a full year. Participants will have an opportunity to author, edit, and earn academic
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xvii


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SECTION I

General Principles

᭤ Behavioral Science
᭤ Biochemistry
᭤ Embryology
᭤ Microbiology
᭤ Immunology
᭤ Pathology
᭤ Pharmacology

1


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CHAPTER 1

Behavioral Science

3

HIGH-YIELD PRINCIPLES
Behavioral Science

4

Section I: General Principles • Questions

Q U E ST I O N S

1. A group of researchers conducted a large double-blind, randomized trial comparing the efficacy of a new antibiotic with penicillin in treating streptococcal pneumonia. The results
showed that 95% of the patients taking the new
antibiotic cleared their pneumonia, while 90%
of those taking penicillin cleared their pneumonia. A large sample size was chosen in order
to generate a statistical power of 80% with a P
value of .21. Which of the following represents
the probability that there is a difference between the two treatment groups despite the
study’s failure to show this difference?
(A) 0.05
(B) 0.20
(C) 0.21
(D) 0.80
(E) 0.90
(F) 0.95
2. A 16-year-old boy is brought to the pediatrician
by his mother because of excessive daytime
sleepiness. She states that over the past 6
months she has received numerous phone calls
from the boy’s school informing her that her
son sleeps throughout all of his afternoon

classes and is often difficult to arouse at the
end of class. The patient reports that occasionally when he wakes up in the morning he cannot move for extended periods. He says that
sometimes when he laughs at jokes or becomes
nervous before a test, he feels as if he cannot
move his legs. He admits that he has even
fallen to the floor because of leg weakness
while laughing. Which of the following is the
best choice for treating this patient?
(A) Chloral hydrate
(B) Hydroxyzine
(C) Modafinil
(D) Prochlorperazine maleate
(E) Zolpidem
3. A 52-year-old woman is being treated by a male
psychiatrist for depression stemming from her

recent divorce. Recently, the patient has been
coming to her appointments dressed up and
wearing expensive perfumes. She has also
started to flirt with the doctor. The patient’s demeanor and appearance had initially reminded
the psychiatrist of his aunt. He is uncomfortable with the patient’s new behavior patterns
and tells her so. She becomes very angry and
storms out of the office, canceling all remaining appointments on her way out. Which of
the following behaviors is an example of negative transference?
(A) The doctor seeing the patient as his aunt
(B) The doctor telling the patient he is uncomfortable
(C) The patient being angry with the doctor
(D) The patient dressing up for appointments
(E) The patient flirting with the doctor
4. A 24-year-old woman presents to her primary

care physician because of depression and insomnia for the past 6 months. The patient
states that she feels bad about herself almost all
of the time. A review of the patient’s history
shows that she has had frequent physician visits
with complaints of stomachaches, headaches,
and fatigue for the past 2 years. Which of the
following characteristics would support a diagnosis of major depressive disorder rather than
dysthymic disorder in this patient?
(A) Changes in appetite
(B) Changes in sleep patterns
(C) Depressed mood
(D) Fatigue/lack of energy
(E) Remittance and recurrence
(F) Two-year duration of symptoms
5. An infant presents to the pediatrician for a routine check-up. His mother reports that he plays
peek-a-boo at home, waves bye-bye, and will say
“dada.” He cannot yet drink from a cup. He
seemed somewhat apprehensive when the physician entered the room. He can lift his head
when lying on his stomach, sit unassisted, and


stand with help. He has a positive Babinski’s reflex. If this infant has met all his developmental
milestones appropriately, how old is he?
(A) 4–5 months
(B) 7–11 months
(C) 12–15 months
(D) 18 months
(E) 24 months

(A) Alcohol

(B) Amphetamines
(C) Cocaine
(D) Lysergic acid diethylamide
(E) Nicotine
(F) Phencyclidine
7. The image below is a common representation
used in studying the characteristics of a test’s
results. Using the letters in the figure, which of
the following accurately describes the prevalence of the disease?

Disease
–

+

W

X

–

Y

Z

Test

+

Reproduced, with permission, from USMLERx.com.

(A) W / (W + X + Y + Z)
(B) (W + X) / (W + X + Y + Z)
(C) W / (X + Y + Z)
(D) W / (X + Z)
(E) (W + Y) / (W + X + Y + Z)
8. A third-year medical resident is driving home
after being on call and witnesses a car accident.
He sees one person leave the car and collapse
at the side of the road. He pulls over to help.
The person appears to be a female in her 30s
with a large laceration across her forehead. She
is barely conscious. Which of the following is
required and/or implied under the Good Samaritan Law?
(A) Compensation for actions
(B) Continued care until emergency services
are contacted
(C) Freedom from legal action
(D) Implied consent of patient in situations in
which patient cannot give voluntary consent
(E) Use of standard procedure
9. A battery of tests is used to evaluate a 13-yearold child’s readiness to skip from seventh to
ninth grade. Both her mother, who has requested the grade change, and many of her
teachers express the belief that she functions
on the intellectual level of most adults. As part
of the battery, she is given an IQ test. Which of
the following is an appropriate IQ test to use?
(A) Iowa Test of Educational Development
(B) Vineland Social Maturity Scale
(C) Wechsler Adult Intelligence Scale-Revised

(D) Wechsler Intelligence Scale for ChildrenRevised
(E) Wide-Range Achievement Test

Behavioral Science

6. A 20-year-old man became very agitated at a
party, and as a result was brought to the emergency department, where he is belligerent and
uncooperative. A physical examination reveals
fever, tachycardia, horizontal nystagmus, and
hyperacusis. Which of the following substances
may cause the behavioral changes and physical
findings exhibited by this patient?

5

HIGH-YIELD PRINCIPLES

Chapter 1: Behavioral Science • Questions


HIGH-YIELD PRINCIPLES
Behavioral Science

6

Section I: General Principles • Questions

10. A 43-year-old woman comes to her physician’s
office extremely nervous because she just
tested positive for HIV according to a newly

designed serum test. Of the 1,000 patients
tested, 200 patients had HIV; the test came
back positive for 180 of them, while the remaining 20 tested negative. Eight hundred of
the patients did not have HIV; however, the
test was positive for 40 of them. The remaining
760 patients tested negative for HIV. Given this
patient’s positive test, which of the following is
the probability that she does have HIV?
(A) 20%
(B) 24%
(C) 82%
(D) 90%
(E) 97%
11. A 56-year-old man presents to his family doctor
for a regular check-up visit. His past medical
history is significant for long-standing hypertension and coronary artery disease. He had a
myocardial infarction and percutaneous angioplasty 1 year ago. The patient initially reports
no complaints, but as his physician is heading
toward the door, the patient states with some
embarrassment that he has had problems
achieving erections since he was released from
the hospital last year. He says that he has morning erections. His current medications include
simvastatin and lisinopril. Which of the following is a likely cause for this man’s acquired
erectile dysfunction?
(A) Decreased interest in sexual activity
(B) Fear of another myocardial infarction
(C) Increasing age of the patient
(D) Medication side effects
(E) Physical inability after the heart attack
12. A 17-year-old girl presents to her primary care

physician with a complaint of missed menses.
Tests reveal she is pregnant. She returns to the
office 2 weeks later asking for recommendations on obtaining an abortion. She explains
that she works, lives with her husband, and is
not ready for a child. She decides that she does
not want to notify anyone, and says she has
chosen not to talk with her parents for many
months. Her doctor understands that he must

abide by her wishes because she is emancipated. Which of the following makes this patient emancipated?
(A) Age 17 years is considered an adult
(B) Full-time work
(C) High school diploma
(D) Living separately from her parents
(E) Marriage
13. A group of oncologists is interested in determining whether a relationship exists between
alcohol use and pancreatic cancer. The researchers enroll 1,000 patients, and subjects
are placed into different groups depending on
their level of alcohol consumption. The subjects are followed for 10 years; the data show
no statistical difference in the number of pancreatic cancers between the groups. The above
research is an example of which of the following kind of study?
(A) Case-control study
(B) Clinical treatment trial
(C) Cross-sectional study
(D) Prospective cohort study
(E) Retrospective cohort study
14. An 11-year-old girl is brought to the pediatrician with complaints of back pain. On physical
examination, a right thoracic scoliotic curve is
noted. An x-ray film indicates that the curve is
25 degrees. Girls with scoliosis need to be especially carefully watched during peak height

velocity, during which the curvature can dramatically worsen. Given that peak height velocity occurs during a particular Tanner stage,
what other physical attributes would one expect to occur in the girl at the same time?
(A) Elevation of the breast papilla only and no
pubic hair
(B) Enlargement of the breast and areola with
a single contour and darker, coarse curled
pubic hair
(C) Mature breast adult quantity and pattern of
pubic hair that extends to the thighs
(D) Projection of the areola and papilla with
separate contours and adult-type pubic
hair limited to the genital area
(E) Small breast buds with elevation of breast