Veterinary clinical epidemiology / Ronald D. Smith.

CONTENTS

CHAPTER 1. INTRODUCTION
I. DEFINITIONS
II. EPIDEMIOLOGIC APPROACHES
A. QUANTITATIVE EPIDEMIOLOGY
B. ECOLOGICAL EPIDEMIOLOGY (MEDICAL ECOLOGY)
C. ETIOLOGIC EPIDEMIOLOGY
D. HERD HEALTH/PREVENTIVE MEDICINE
E. CLINICAL EPIDEMIOLOGY
III. APPLICATIONS OF EPIDEMIOLOGY IN VETERINARY PRACTICE
IV. OBJECTIVES
A. DEVELOPMENT OF MEDICAL DECISION-MAKING SKILLS
B. LEARN EPIDEMIOLOGIC METHODOLOGY
C. LEARN TO READ THE MEDICAL LITERATURE CRITICALLY
V. SUMMARY

CHAPTER 2. DEFINING THE LIMITS OF NORMALITY
I. INTRODUCTION
II. PROPERTIES OF CLINICAL MEASUREMENTS
A. SIGNS AND SYMPTOMS: OBJECTIVE VERSUS SUBJECTIVE DATA
B. SCALES
C. CLINICAL STAGING
D. VALIDITY AND RELIABILITY
E. VARIATION
1. Measurement Variation
2. Biological Variation
3. Reducing the Effects of Variation
III. DISTRIBUTIONS
A. BASIC PROPERTIES OF DISTRIBUTIONS
B. SHAPES OF NATURALLY OCCURRING DISTRIBUTIONS
1. Unimodal, Bimodal and Multimodal
2. Symmetry, Skewness and Kurtosis
3. Factors Influencing the Shape of Frequency Distributions
C. THE NORMAL DISTRIBUTION
IV. REFERENCE RANGES AND THE CRITERIA FOR ABNORMALITY
A. ABNORMAL AS UNUSUAL
B. ABNORMAL AS ASSOCIATED WITH DISEASE
C. ABNORMAL AS DETECTABLE OR TREATABLE
V. SUMMARY

CHAPTER 3. EVALUATION OF DIAGNOSTIC TESTS
I. INTRODUCTION
II. TEST ACCURACY
A. THE STANDARD OF VALIDITY (GOLD STANDARD)
B. POSTMORTEM EXAMINATION AS A DIAGNOSTIC TEST
III. PROPERTIES OF DIAGNOSTIC TESTS
A. SENSITIVITY AND SPECIFICITY (TRUE-POSITIVE AND -NEGATIVE RATES)
B. FALSE POSITIVE AND NEGATIVE RATES
C. PREDICTIVE VALUES
D. THE EFFECT OF PREVALENCE ON PREDICTIVE VALUES
E. LIKELIHOOD RATIOS
F. ACCURACY, REPRODUCIBILITY AND CONCORDANCE
IV. INTERPRETATION OF TESTS WHOSE RESULTS FALL ON A CONTINUUM
A. TRADE-OFFS BETWEEN SENSITIVITY AND SPECIFICITY
B. RECEIVER OPERATING CHARACTERISTIC (ROC) CURVE
C. TWO-GRAPH RECEIVER OPERATING CHARACTERISTIC (ROC) ANALYSIS
D. SELECTING A CUTOFF
V. COMPARISON OF DIAGNOSTIC TESTS
A. FOR TESTS WITH FIXED CUTOFFS
B. FOR TEST RESULTS THAT FALL ON A CONTINUUM
VI. SOURCES OF BIAS IN THE EVALUATION OF DIAGNOSTIC TESTS
A. RELATIVE VERSUS TRUE SENSITIVITY AND SPECIFICITY
B. THE SPECTRUM OF PATIENTS
C. BIAS IN ASSOCIATING TEST RESULTS WITH DISEASE
VII. STATISTICAL SIGNIFICANCE
VIII. SUMMARY

CHAPTER 4. USE OF DIAGNOSTIC TESTS
I. INTRODUCTION
II. CALCULATION OF THE PROBABILITY OF DISEASE
A. FROM A TWO-BY-TWO TABLE
B. USE OF BAYES' THEOREM
B. USE OF THE LIKELIHOOD RATIO TO CALCULATE POST-TEST PROBABILITIES
1. Conversion Between the Probability of Disease and the Odds of Disease
2. Calculation of the Post-Test Probability of Disease
3. A Nomogram for Applying Likelihood Ratios and Bayes' Theorem
4. Estimating Post-Test Probability of Disease from the Magnitude of a Test Result
D. USE OF POST-TEST PROBABILITIES IN MEDICAL DECISION-MAKING
III. MULTIPLE TESTS
A. PARALLEL TESTING
B. SERIAL TESTING
C. HERD RETEST
D. ASSUMPTION OF INDEPENDENCE OF MULTIPLE TEST RESULTS
IV. WORKING WITH DIFFERENTIAL LISTS
A. RULE-INS AND RULE-OUTS: THE CHOICE OF SENSITIVE OR SPECIFIC TESTS
V. SCREENING FOR DISEASE
A. DEFINITIONS
B. TEST CRITERIA
VI. INCREASING THE PREDICTIVE VALUE OF DIAGNOSTIC TESTS
VII. COMMUNICATIONOF DIAGNOSTIC TEST RESULTS
VIII. SUMMARY

CHAPTER 5. MEASURING THE COMMONNESS OF DISEASE
I. INTRODUCTION
II. EXPRESSING THE FREQUENCY OF CLINICAL EVENTS
A. PROPORTIONS, RATES AND RATIOS
B. PREVALENCE, INCIDENCE AND ATTACK RATE
III. MEASURING THE FREQUENCY OF CLINICAL EVENTS
A. PREVALENCE
B. INCIDENCE
IV. FACTORS AFFECTING THE INTERPRETATION OF INCIDENCE AND PREVALENCE
A. TEMPORAL SEQUENCE
B. DISEASE DURATION
C. RELATIONSHIP AMONG INCIDENCE, PREVALENCE AND DURATION OF DISEASE
D. TRUE VERSUS APPARENT PREVALENCE
E. CASE DEFINITION
F. DANGLING NUMERATORS
G. POPULATION AT RISK
H. CRUDE VERSUS ADJUSTED RATES
V. ADJUSTED RATES: THE DIRECT METHOD
A. AGE-ADJUSTED RATES
B. RATE ADJUSTMENT FOR OTHER FACTORS
C. THE CHOICE OF A STANDARD POPULATION
D. WHEN TO ADJUST RATES
E. THE USES OF INCIDENCE AND PREVALENCE
VI. SUMMARY

CHAPTER 6. RISK ASSESSMENT AND PREVENTION
I. RISK FACTORS AND THEIR IDENTIFICATION
II. FACTORS THAT INTERFERE WITH THE ASSESSMENT OF RISK
III. USES OF RISK
IV. COMPARISON OF RISKS
A. UNIVARIATE ANALYSIS
B. MULTIVARIATE ANALYSIS
1. Mantel-Haenszel Stratified Analysis
2. Multivariate Logistic Regression Analysis
V. COHORT STUDIES OF RISK
A. TRUE COHORT STUDY DESIGNS
1. Concurrent Cohort Studies
2. Historical Cohort Studies
B. SURVIVAL COHORTS
C. LIMITATIONS OF COHORT STUDIES
D. COMPARING RISKS IN COHORT STUDIES
1. Relative Risk
2. Attributable Risk
3. Population Attributable Risk
4. Population Attributable Fraction
VI. CASE CONTROL STUDIES OF RISK
A. ADVANTAGES OF CASE CONTROL STUDIES
B. COMPARING RISKS IN CASE CONTROL STUDIES
C. THE ODDS RATIO
D. BIAS IN CASE CONTROL STUDIES
1. Bias in Selecting Groups
2. Bias in Measuring Exposure
3. Presumed Temporal Relationships
VII. PREVALENCE SURVEYS OF RISK
A. COMPARING RISKS IN PREVALENCE SURVEYS
B. LIMITATIONS OF PREVALENCE SURVEYS
VIII. BIOLOGICAL PLAUSIBILITY AND CROSS-SECTIONAL STUDY DESIGNS
IX. SUMMARY

CHAPTER 7. MEASURING AND COMMUNICATING PROGNOSES
I. EXPRESSING PROGNOSES
II. NATURAL HISTORY VERSUS CLINICAL COURSE
III. PROGNOSIS AS A RATE
IV. SURVIVAL ANALYSIS
A. SURVIVAL OF A COHORT
1. Steady-State Population Models
2. Vital Statistics Data
3. Clinical Trials
B. LIFE TABLE ANALYSIS
C. INTERPRETING SURVIVAL CURVES
V. COMMUNICATION OF PROGNOSES
VI. SUMMARY

CHAPTER 8. DESIGN AND EVALUATION OF CLINICAL TRIALS
I. INTRODUCTION
II. EFFICACY, EFFECTIVENESS AND COMPLIANCE
III. CLINICAL TRIALS: STRUCTURE AND EVALUATION
A. CASE DEFINITION
B. UNCONTROLLED CLINICAL TRIALS
C. COMPARISONS ACROSS TIME AND PLACE
D. ALLOCATING TREATMENT
E. REMAINING IN ASSIGNED TREATMENT GROUPS
F. ASSESSMENT OF OUTCOME
G. PLACEBO EFFECT
H. STATISTICAL ANALYSIS
IV. SUBGROUPS
V. CLINICAL TRIALS IN PRACTICE
VI. SUMMARY

CHAPTER 9. STATISTICAL SIGNIFICANCE
I. INTRODUCTION
II. HYPOTHESIS DEFINITION AND TESTING - AN OVERVIEW
III. INTERPRETATION OF STATISTICAL ANALYSES
A. CONCLUDING A DIFFERENCE EXISTS
1. The Null Hypothesis
2. Statistical Significance
3. Confidence Intervals
4. Confidence Interval for a Rate or Proportion
5. One-Tailed Versus Two-Tailed Tests of Significance
B. CONCLUDING A DIFFERENCE DOES NOT EXIST
1. Statistical Significance
2. Power
C. CONCLUDING AN ASSOCIATION EXISTS
1. Agreement Between Tests
2. Association Between Two Variables
IV. THE SELECTION OF AN APPROPRIATE STATISTICAL TEST
A. LEVEL OF MEASUREMENT
B. NUMBER OF GROUPS
C. NATURE OF GROUPS
D. NUMBER OF CATEGORIES
E. CATEGORY SIZE
F. DATA
V. PARAMETRIC AND NONPARAMETRIC TESTS
VI. SAMPLE SIZE
A. MINIMUM SAMPLE SIZE FOR DEMONSTRATING AN EXTREME OUTCOME
B. MINIMUM SAMPLE SIZE FOR ESTIMATING A RATE WITH A SPECIFIED DEGREE OF PRECISION
C. MINIMUM SAMPLE SIZE TO DETECT DIFFERENCES AMONG GROUPS
VII. SAMPLING STRATEGIES
A. PROBABILITY SAMPLING
1. Simple Random Sampling
2. Systematic Sampling
3. Stratified Random Sampling
4. Cluster Sampling
B. NONPROBABILITY SAMPLING
1. Consecutive Sampling
2. Convenience Sampling
3. Judgmental Sampling
VIII. MULTIPLE COMPARISONS
IX. SUMMARY

CHAPTER 10. MEDICAL ECOLOGY AND OUTBREAK INVESTIGATION
I. INTRODUCTION
II. ISSUES IN THE EPIDEMIOLOGY OF A DISEASE
A. OCCURRENCE
B. CAUSE
C. SUSCEPTIBILITY
D. SOURCE
E. TRANSMISSION
F. COST
G. CONTROL
III. OUTBREAK INVESTIGATION
A. DESCRIPTIVE PHASE (SUBJECTIVE, OBJECTIVE DATA)
B. ANALYTIC PHASE (ASSESSMENT)
C. INTERVENTION (PLAN)
IV. SUMMARY

CHAPTER 11. MEASURING AND EXPRESSING OCCURRENCE
I. INTRODUCTION
II. CASE DEFINITION
A. BASED ON DISEASE SIGNS, SYMPTOMS AND EPIDEMIOLOGY
B. BASED ON PERFORMANCE
III. REPORTING DISEASE OCCURRENCE
A. HOST DISTRIBUTION
1. Attack Rate
2. Crude Versus Adjusted Rates
B. TEMPORAL DISTRIBUTION
1. Sporadic Disease
2. Endemic Disease
3. Epidemic Disease (Outbreak)
C. TIME SERIES ANALYSIS
D. SPATIAL DISTRIBUTION
IV. CASE STUDY
A. THE EPIDEMIC OF WEST NILE VIRUS IN THE UNITED STATES, 2002
1. Introduction
2. Purpose of the Study
3. Epidemiologic Methodology
4. Assumptions Inherent in the Methodology
5. Basic Epidemiologic Findings
6. Conclusions and Measures Taken
V. SUMMARY

CHAPTER 12. ESTABLISHING CAUSE
I. INTRODUCTION
II. MULTIPLE CAUSATION OF DISEASE
A. AGENT FACTORS
B. HOST FACTORS: SUSCEPTIBILITY
C. ENVIRONMENTAL (MANAGEMENT) FACTORS
III. SOURCES OF BIAS IN EVALUATING CAUSE-EFFECT RELATIONSHIPS
A. CONFOUNDING
B. INTERACTION OR EFFECT MODIFICATION
C. MULTICOLLINEARITY
D. PROCEDURE FOR EVALUATING INTERACTION AND CONFOUNDING
E. THE CHOICE OF MULTIVARIABLE VERSUS STRATIFIED ANALYSIS
IV. ESTABLISHING CAUSE
A. STRENGTH OF STUDY DESIGNS
B. TEMPORAL RELATIONSHIP BETWEEN CAUSE AND EFFECT
C. STRENGTH OF THE ASSOCIATION
D. DOSE-RESPONSE RELATIONSHIP
E. BIOLOGICAL PLAUSIBILITY
F. CONSISTENCY
G. ELIMINATION OF OTHER POSSIBILITIES (RULE OUT)
H. REVERSIBLE ASSOCIATIONS
V. CASE STUDY
A. CASE-CONTROL STUDY OF FACTORS ASSOCIATED WITH EXCESSIVE PROPORTIONS OF EARLY FETAL LOSSES ASSOCIATED WITH MARE REPRODUCTIVE LOSS SYNDROME IN CENTRAL KENTUCKY DURING 2001
1. Introduction
2. Purpose of the Study
3. Epidemiologic Methodology
4. Assumptions Inherent in the Methodology
5. Basic Epidemiologic Findings
6. Conclusions and Measures Taken
VI. SUMMARY

CHAPTER 13. SOURCE AND TRANSMISSION OF DISEASE AGENTS
I. SOURCES OF INFECTION
A. IATROGENIC INFECTIONS
B. ANIMAL RESERVOIRS
C. ENVIRONMENT
II. TRANSMISSION
A. MODE OF TRANSMISSION VERSUS ROUTE OF INFECTION
B. TRANSMISSIBLE VERSUS NONTRANSMISSIBLE DISEASES
III. MODES OF TRANSMISSION
A. HORIZONTAL TRANSMISSION
1. Direct Transmission
2. Indirect Transmission
3. Airborne Transmission
B. VERTICAL TRANSMISSION
IV. FACTORS AFFECTING COMMUNICABILITY
A. AGENT FACTORS
1. Life Cycle
2. Minimal Infective Dose
B. HOST FACTORS
1. Heterogeneity
2. Immunity
C. ENVIRONMENTAL FACTORS
1. Particle Diameter
2. Microclimate
V. CASE STUDY
A. AN OUTBREAK OF ESCHERICHIA COLI O157:H7 INFECTIONS AMONG VISITORS TO A DAIRY FARM
1. Introduction
2. Purpose of the Study
3. Epidemiologic Methodology
4. Assumptions Inherent in the Methodology
5. Basic Epidemiologic Findings
6. Conclusions and Measures Taken
VI. SUMMARY

CHAPTER 14. THE COST OF DISEASE
I. DEFINING DISEASE IN ECONOMIC TERMS
A. THE MEASURES OF EFFECT APPROACH TO ESTIMATING DISEASE IMPACT
B. PARTIAL BUDGETING AND COST-BENEFIT ANALYSIS
1. Partial Budgeting
2. Cost-Benefit Analysis
3. Discounting, Present and Future Value of Money
4. Decision Criteria in Cost-Benefit Analysis
II. DECISION ANALYSIS
A. STEPS IN BUILDING A DECISION TREE
1. Nodes
2. Utilities
3. Variables
B. ANALYSIS OF THE DECISION TREE
1. Fold Back
2. Sensitivity Analysis
3. Risk Profile Analysis
III. STRATEGIES TO REDUCE THE FREQUENCY OF DISEASE
A. DISEASE PREVENTION
B. DISEASE CONTROL
C. DISEASE ERADICATION
1. Test and Removal versus Herd Depopulation
2. Necessary Conditions for Eradication
IV. CASE STUDY
A. POTENTIAL REVENUE IMPACT OF AN OUTBREAK OF FOOT-AND-MOUTH DISEASE IN THE UNITED STATES
1. Introduction
1. Purpose of the Study
3. Epidemiologic Methodology
4. Assumptions Inherent in the Methodology
5. Basic Epidemiologic Findings
6. Conclusions and Measures Taken
V. SUMMARY

Includes bibliographical references (p. 243-249) and index.