p
`DICTIONARY
`i
`Oi
`' Epidemiology
`Sitett
`
`Miquel Porta
`
`Edited by
`
`CELGENE 2107
`APOTEX v. CELGENE
`IPR2023-00512
`
`

`

`A Dictionary of Epidemiology
`
`

`

`a A
`a"
`Dictionary
`of
`Epidemiology
`
`Fifth Edition
`
`Edited for the
`International Epidemiological Association
`by
`Miquel Porta
`Professor of Preventive Medicine & Public Health
`School of Medicine, Universitat Autonoma de Barcelona
`Senior Scientist, Institut Municipal d’Investigacié Médica
`Barcelona, Spain
`Adjunct Professor of Epidemiology, School ofPublic Health
`University of North Carolina at Chapel Hill
`
`Associate Editors
`Sander Greenland
`John M. Last
`
`OXFORD
`UNIVERSITY PRESS
`
`2008
`
`

`

`fhe Te
`ces
`
`“OXFORD
`|. |: UUNVERSITY PRESS
`
`Oxford University Press, Inc.,publishes works that further
`Oxford University’s objective excellence
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`Copyright © 1983, 1988, 1995, 2001, 2008 International Epidemiological Association,Inc.
`
`Published by Oxford University Press, Inc.
`198 Madison Avenue, New York, New York 10016
`www.oup-usa.org
`
`All rights reserved. No part of this publication may be reproduced,
`stored in a retrieval system, or transmitted, in any form or by any means,
`electronic, mechanical, photocopying, recording, or otherwise,
`.
`without the prior permission of Oxford University Press.
`
`This edition was prepared with support from -
`Esteve Foundation (Barcelona, Catalonia, Spain)
`(http://www.esteve.org)
`
`Library of Congress Cataloging-in-Publication Data
`A dictionary of epidemiology /
`edited for the International Epidemiological Association
`by Miquel Porta;
`associate editors, John M. Last .. . [et al.].—5th ed.
`p.cm.
`Includes bibliographical references and index.
`ISBN 978—0-19-531449—6 ISBN 978—0-19-531450—2 (pbk.)
`1. Epidemiology—Dictionaries.
`I. Porta, Miquel—
`IL. International Epidemiological Association.
`RA651.D553 2000
`
`614.4’03—dc21 00—-037504
`
`246897531
`
`Printed in the United States of America
`
`on acid-free paper
`
`RZetle3a$}yF/3
`
`

`

`Semi-individual design
`226
`aims and design. Examples of potential reasons for selection bias include surveys
`limited to volunteers or to persons present in a particular place at a particular time,
`studies based on disease survivors; hospital-based studies that cannot include patients
`whodie before hospital admission due to acute illness or that do not include persons
`with mild conditions, which seldom require hospital care; case-control studies in
`which selection of cases and controls is differentially influenced by cost, distance,
`concomitantillnesses, access to diagnostic procedures, or other factors.'°!™ Selection
`biases may be related to CONFOUNDING and INFORMATIONBIASES.*! In CLINICAL TRIALS,
`two kinds of selection bias are especially relevant: sample selection bias or SAMPLING
`BIAS (systematic differences among participants and nonparticipants in trials) and
`ATTRITION BIAS (systematic differences due to selective loss of subjects, also known as
`follow-up bias).
`Selection bias can virtually never be corrected bystatistical analysis. It is a common and
`commonly overlooked problem,not just in epidemiological studies but also in clinical
`and basic biological studies. See also BERKSON’S BIAS; CONSENT BIAS; CONTROLS, HOSPITAL,
`INCEPTION COHORT.
`SEMI-INDIVIDUAL DESIGN Individual-level studies (e.g., COHORT STUDIES, CROSS-SECTIONAL
`STUDIES, CASE-CONTROL STUDIES) in which outcome and covariates are measured at the
`individual level while exposure is characterized on the aggregate (or ecological) level.
`Used either because groups share the same exposure or because individual-level expo-
`sure ‘measures are not available. Frequently used in environmental epidemiology to
`describe exposure to air, water, or soil pollutants. Not to be confused with ECOLOGICAL
`STUDIES. 107358
`SEMIOLOGY (Syn: symptomatology)
`1. In medicine, the study of signs and symptoms of disease. Their relevance to the
`practice of clinical medicine has long been recognized. They are important also
`to epidemiology--related activities like HEALTH SERVICES RESEARCH (e.g., when
`quality assurance programs monitor intervals from first symptom of disease to
`first consultation, diagnosis, and treatment). Symptoms and signs are also relevant
`to etiological research because they often reflect underlying pathophysiological
`processes that may alter levels of the exposures understudy (e.g., when disease
`progression entails metabolic changes that alter exposure biomarkers). The analysis
`of the attribution of meaning to signs and symptomsis essential to understand the
`SICKNESS “CAREER’’?!24128 and hence to PREVENTIVE MEDICINE, EARLY CLINICAL DETECTION,
`and clinical care. See also SYNDROME.
`2. The study of signs, signals, and symbols, especially the relationship between written
`and spoken language.**?
`SENSITIVE PERIOD (Syn:critical period) A time during the developmentofa tissue,
`organ, or system when it can be permanently changed by harmful influences (e.g.,
`undernutrition, hypoxia, stress). It often coincides with a period of rapid cell division
`and, for many tissues and systems, occurs before birth. The brain andliver are the main
`organs that remain plastic after birth.** The adverse (or protective) effects,on health of
`exposures during a sensitive period may be apparent manyyearslater. See also DEVELOP-
`MENTAL ORIGINS HYPOTHESIS; PLASTICITY; PROGRAMMING; VULNERABILITY.
`SENSITIVITY ANALYSIS A method to determine the ROBUSTNESS of an assessment:
`by examining the extent to which results are affected by changes in methods, models,
`values of unmeasured variables, or assumptions.* The aim is to identify results that
`
`

`

`227
`
`Sentinel physician, sentinel practice
`
`are most dependent on questionable or unsupported assumptions. See also INFLUENCE
`ANALYSIS; OUTLIERS.
`SENSITIVITY AND SPECIFICITY (of a screening test, of a diagnostic test):
`1. Sensitivity is the probability that a diseased person (case) in the population tested
`will be identified as diseased by the test (syn: true positive probability). Sensitivity is
`thus the probability of correctly diagnosing a case or the probability that any given
`case will be identified by the test (syn: true-positive rate).
`2. Specificity is the probability that a person without the disease (noncase) will be
`correctly identified as nondiseased by thetest. It is thus the probability of correctly
`identifying a nondiseased person with a test (syn: true-negative probability).
`The relationships are shownin the following fourfold table, in which the letters a, b, c, and
`d represent the numbersin the table below.
`
`Screening test results
`
`True status
`Diseased
`Not diseased
`
`Total
`
`Positive
`Negative
`Total
`
`a
`c
`ate
`
`b
`d
`b+d
`
`a+b
`c+d
`at+t+b+ce+d
`
`a. Diseased individuals detected by the test (true positives)
`b. Nondiseased individuals positive by the test (false positives)
`c. Diseased individuals not detectable by the test (false negatives)
`d. Nondiseased individuals negative by the test (true negatives)
`
`Sensitivity =
`
`
`
`atc
`
`Specificity =
`
`
`
`b+d
`
`Predictive value of a positive test result =
`
`5at
`
`Predictive value of a negative test result =
`
`=c+
`
`at+d
`Accuracy = ———---_____-
`a+b+c+d
`
`The predictive value of a positive test result may be called the yield. See also LIKELIHOOD
`RATIO; PREDICTIVE VALUE.
`SENSITIVITY TESTING A study of how the final outcome of an analysis changes as a
`function of varying one or more of the input parameters in a prescribed manner. See
`also SENSITIVITY ANALYSIS.
`SENTINEL HEALTH EVENT A condition that can be used to assess the stability
`or change in health levels of a population, usually by monitoring mortality statistics.
`Thus, death due to acute head injury is a sentinel event for a class of severe traffic
`injury that may be reduced by such preventive measures as use of seat belts and crash
`helmets.
`SENTINEL PHYSICIAN, SENTINEL PRACTICE In family medicine, a physician or
`practice that undertakes to maintain surveillance for and to report certain specific
`
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`A “AWNi
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