Table Of ContentAppleton & Lange's Review of
EPIDEMIOLOGY
& BIOSTATISTICS
FOR THE USMLE
. MD
GANGADHAR MADUPU, MBBS, MS
=
APELBTON & LANGE
Norwalk, Conesticut
ISBN 0-9985-0046-8
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Libvary of Congress Cataloging-in-Publication Data
Flaneghan, Baward J
“Appleton & Lange's review of epidericlogy & biosatistis forthe
‘USRILE award Hanahan, Gangedhar Madu
ors
Inde nex,
IBN 0-6058-0246
1 Bpldimislogy—Beamlnatens, questions, 2 Bierclay
saminatlan, questions, et. 8. Siatistico—Uraminations,
queria ola. 4 Medial reatstioe—Ssminetins, ques.o08,
gE Meco, Gangedhar, 1, Title. IE. ite Aypltan and
Lange's roviow of opidemiolog & biostotitics fr the UEASLE,
By. Tier Epicelogy & blestatiotes fr the USE.
ONLM: 1. Rpidemicegy—snaminntion gestions, & Statitiee—
examination quctions, WA 1SH2460 1994],
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‘Production Bdtor Sondra Greenteld
Designer: TopDeek Pubichere Group
PRINTED IN THE UNITED STATES OF AMBRICA
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ui i
Contents
Preface.
Introduction
How ta Use This Book.
‘Acknowledgments
Essential Concepts.
Chapter 1. Epidemiological Terminology.
Chupler 2, Classifications of Epidemics.
Chapter &, The 2-by-2 Table and Its Concepts,
Chapter 4. Hypothesis Testing
Chapter 5. Minsures af Morbidity and Slortality
Chapter 6. Bpidamiotogial Study Neng and Measures
EBA cnn
Chapter 7. The N
Chapter 8. Statistical Teste...
Chapter 9. The Correlation Guclfsiont ant
Regression Aualysis,
Chapter 10, Practice Te
Answers and Explanations
Appendix A. Formula Summary.
‘Appendix B. Students t Distribution Table
‘Appendix C. Chi-square Distributiua Table..
‘Appendix D, Commonly Used Statistical Symbols.
Index
Practice Test Answer Sheet.
Anewers to Chapter Questions.
Preface
‘This bovk hus heen wrilien primarily for medical students and
{intamnational medical graduates preparing for the United States
Medical Liosnsing Examinations. Itz aim is to present the core
material that the modical etudent needs to euooesufully completa
the epidemiology and biostatistics sections of those examinations.
‘Thia hook is not designed to he a comsprehensive text but, rather,
an outline of the essentials thnt eau be xead and reviewed in a
limited amet of ima,
‘The authors feel that the essentials of epidemiology and bio-
statisties enn be mastered very quickly with the una of this ra-
‘view, and they sugzest that it be read from cover to cover,
Gongudhar Madupa, MBBS, MB
Introduction
In the contemporary arena of modical certification, board exami
nations administered hy the National Board of Medical Exemin-
erm (NTN) have become increasingly difficult. Madieul sudeats
‘and international medical graduates ara constantly on the look
‘out for a concisa book in every subject, including epidemiology
‘and biosLaListies, to facllitate preparation for thece examinations,
‘The right kind of review must he broad in scope to permit atten-
aa to the important aspects of each discipline, yet enncie
enough te facilitate lewrning within time cmetraints, The United
States Medical Licensing Examinations USWLR) Step 1, Slop 2,
and Step 3 hav been designed to measvre comprehensive knowl
edge and the ubilily to apply thot knowledge eliaically. the
NBME recammends that the most appropriaie preparation is 9
gencral and thorough review of the haste and clinical seienca.
‘Mast of the backs written on the topics of epidemiology and bio
statistice exceed 300 payes in length. ‘They lack the brevity Lat.
time constraints necossilatc in the burgeoning enrriculam of the
‘medical examinve. Beeause questions pertaining to epidemiology
and biostatistics appear in all three eteps of the USMLE, our on
eavor is to inLsidues a shot, eoncise review book that (1) clearly
(gets ta the paint on the essential material, (2) proscuts core mate-
ial clearly and succinctly in a medically relovant and clinically
‘understandable format, and (2) most important, teste the reader
swith hoard types of questions both within the topie discussions as
‘well aa in a eeparate timed examination.
‘The Baiors ond the Publisher
How to Use This Book
‘Thia back assiste your proparation for the USMLE by providing
aan aulline of etudy deaigns, statistion) methods, aad their clinieal
significance in oonlemporusy snvdical practice, It lustrates how
sthien may Int compared (ANOVA, chi-square, ¢ tes, correlie
‘Hon, and near recession analysis, and 90 on); hnss relative and
attribulable sisha aud odds ratiog characterize indapandent varie
fables as they relate to optcome (dependant variables), how a par~
ticular treatment regimen can be shown to he superior to another
bby using standard statistical melhodclogies; how primary preven-
tion atrategien revtucn the invidenco of disease, a9 Well as the mer-
Fhidity and mortality associated sith neenndary und Lertiary pre-
‘ventioa; and finally, how to view a sruph, table, or chiart to
Aclormine exactly what it eonvuys.
All these concepts are tusted Lupies on Step 1 and Step 2 of the
USNILE smd are presented here for your review in a rapid read
ing format. The fuudusneutal goal of this book is to deliver a con
‘oeptuitizalion that can be ready aasimited and lu equip you
swith the ability to quickly answer questions on opidemiology and
‘ioutatistis,
‘Hor those of you with a strong proficicney in these two areas of
mmediicine, go straight to Appendix A, review the formulus, and
proceed diruelly lo Lhe imed examination at the end of the buck.
‘After completing the test, check your angwery uid review the ap-
propriate sections for the quertiona that ware answered incor
eelly.
For a more comprehensive reviews begin with the frst chapter
and review ench lopic before taking the prectice examination,
‘Qnuw you samplete the subject review, take the praclice examina
tion. Chock your answere, and review the weolions (a second time)
that are appropriate for the incorrectly answered questions.
‘The authors wish to express their confidence thet the time
taken by USMLE candidates to master this sbudy guide will be
time wisely spent.
Edward J. Hanrahan, MD
a
Acknowledgments
I would Jike to express: my indebtedness to Elizabeth Storm,
‘PhD, MS, chairperson of the Department of Epidemivlugy and
Biostatistics at Rose Univeraiy School of Medicine, without whose
distinguished lectures my interest in epidemiologic and hiostatis
tical methodologies in medicine might nevor have materialized.
‘To my closest frierd, Bill Beach, Til bo clernally grateful for all,
his PC exportive and personal sacrifices that made this book a re-
ality. And alchough it is impossible ever to adequately thunk. ny
family for sll the support and encouragement that they have
siven me throughout the years, Mom. . . Hove you,
Rawerd J. Hanrahan, MD
Tam deeply indebted to the fueulty of the Department of Social
and Preventative Medicine (Epidemiology) of the State Univer-
pity of New York at Buifalo, Special thanks to Tim E. Byera,
MD, MPH, a distinguished cancer epidemiclogist, and Maria
ulvang, PhD, biostatistician, an outstanding toncher whose de-
partmaental lectures for mavter'r-level graduule studies at the
State University of New York at Bullalo served as the knowledge
base for thie hook. Yam also thankful to my family members, e-
pecially my brother Murali for his financial agsistance during my
years of schooling at Duffalo, Finally, [would dike te thank all the
‘students to whom I have taught epidemiology and biostatistics
{nr providing me with the necessary experience Lo make this hook
possible.
Gangadhar Madupv, MEBS, MS,
at
CHAPTER t
Epidemiological Terminology
11 Epidomiotogy
Epidemiology refers to the inventiqution of factors that determine
the frequency and distribution aT disease or other health-related
conditions within s defined human population during a specified
period.
12 Epidemics
‘An epidemic is an inereace in the incidence of disouses, condi-
tions, or othar hoolih-related events in a defined human popula
tion that fe eloorly in excoss of that which waa expected during a
specified periud. Although the presence of the disuse or event is
typically occasional in a particular eummmunity, ils opidemicity is
alwaya rolative to ite penal frequency ia terms of time, place, and
population, Outhreska thet affee. lange numbers of animals are
referred to as epizootic.
18 Endemies
Endomis are diseases, conditions, or health-velated behaviors
‘that are convtantly present in a human papolation. An endemic
‘may he referred to as the usual prevalence of an event ar ooeur-
anes in a defined community, Endemies that oecasionally or sear
sonally bocome epidemic are refurred to a8 endemoepidemécs, and
those that are present at a high rate of incidence and affect all
ages equally are called Ayperendemics.
44 Pandomics
Pandemies are widesproad epidemics that achieve large geo-
‘graphic proportions,
Example
During the influenza pandemic of the 19th cankury, millions of
‘people neross the continents were uffevied. Today, AIDS is consid
‘ered lo be the most alarming pandemic of the century.
ec Sg at Sts
1.8 Primary Prevention
Primary prevention is a reduction in the incidence of disease
through immunization, sanitation, education, or other means of
‘liniuating pathogenic contamination in the humen environ
mont.
Examples
Preschool diphtheriv/pertuscivlctanus (DPT) immunization of
childzen, polio and in uenza vaccinations, and so gn.
QL. All the fillowing activities meot (ho criteria for primary
prevention except
(A) telanus vaccination for taenayers
(B) measles/mornpefrubella (MALE) vaccination for fist
time-pregnant mothers
(©) duerifiestion of water
) pap pmuene norcening
(B) sax education
16 Secondary Prevontion
‘Secondary prevention is the early detection and treatment of dise
Example
Pap smears for the early detection of cervical emneer and surgical
interventinn i necessary.
1.7 Tertiary Prevention
‘Tertiary prevention ip tha reduction of the complications of dis-
eases and the improvemant in the patient's Ievel of funelion
‘through palliative treatment and rehabilitation therapy.
Example
Shortly after the occurrence of hemiplegia secondary ta stroke,
‘bed care and physiotherapy are employed to prevent the develop
‘ment of decubitus ulecrs and flexion contractures,
1.8 Spectrum of an Infectious Disense
"The sequence of events baginning with the exposure of a suscepti-
le individu lo an pathogenic agent and ending with a patient's
recovery or death is illustrated in the following diagram.
