Practical Clinical Epidemiology for the Veterinarian

CONTENTS

Cover

Title page

Preface

Acknowledgments

About the companion website

1 Describing health and disease

Case definition

Types of measurements

Specific measurements of disease

2 Basic epidemiology concepts

Outcome

Risk factor

Unit of analysis

Variables

Control groups

Sample size and P-value

Error and bias

Confounding

Interaction

3 Evidence-based medicine for the veterinarian

Evaluation of a research paper

Data presentation in the results

Interpretation of results

4 Study designs

Retrospective studies

Cross-sectional studies

Prospective studies

Sampling strategies

5 Causation versus association

Hill’s criteria to determine causation

Measures of association

6 Diagnostic tests

Test quality

Test performance

Screening

Gold standard

7 Outbreak investigations

Definitions

Steps in an outbreak investigation

Glossary

Formulas

Final word

References

Index

End User License Agreement

List of Tables

Chapter 02

Table 2.1 Graphic representation of the types of errors in statistical analyses.

Chapter 03

Table 3.1 Reported association strength of chloramphenicol-resistant Salmonella infections in humans with different studied risk factors.

Chapter 05

Table 5.1 Organization of a 2 × 2 table for analysis of risk factors.

Table 5.2 Simplified layout of a 2 × 2 table for analysis of risk factors.

Table 5.3 Organization of the 2 × 2 table for analysis of exposure to pasture as a risk factor for injuries in horses.

Table 5.4 Organization of the 2 × 2 table for analysis of exposure to pasture as a risk factor for injuries in horses (alternative coding).

Table 5.5 Organization of the 2 × 2 table for analysis of exposure to multiple pets as a risk factor for behavioral problems in dogs.

Table 5.6 Organization of the 2 × 2 table for analysis of exposure to multiple pets as a risk factor for behavioral problems in dogs (alternative coding).

Table 5.7 Visualization of the calculation of the odds ratio.

Table 5.8 Setup of the 2 × 2 table with information from a study on lame horses.

Table 5.9 Calculation of empty cells in a 2 × 2 table based on existing data on lame horses.

Table 5.10 Setup of the 2 × 2 table with information from a study on viremia in cats vaccinated against feline leukemia.

Table 5.11 Calculation of empty cells in a 2 × 2 table based on existing data on viremia in cats vaccinated against feline leukemia.

Table 5.12 Setup of the 2×2 table with information from a study on viremia in cats vaccinated against feline leukemia, assuming that vaccination against feline leukemia is protective.

Table 5.13 Organization of the 2 × 2 table for evaluation of vaccination against feline leukemia as a risk factor for fibrosarcoma in cats.

Table 5.14 Setup of the 2 × 2 table with information from a study on vaccine-associated tumor in cats vaccinated against feline leukemia.

Table 5.15 Setup of the 2 × 2 table with information from a study on the effect of spaying on the development of mammary cancer in dogs.

Table 5.16 Calculation of empty cells in a 2 × 2 table based on existing data on the effect of spaying on the development of mammary cancer in dogs.

Table 5.17 Alternate setup of the 2 × 2 table with information from a study on the effect of spaying on the development of mammary cancer in dogs.

Table 5.18 Alternate naming of the exposure variable in the 2 × 2 table with informationfrom a study on the effect of spaying on the development of mammary cancer in dogs.

Chapter 06

Table 6.1 Organization of a 2 × 2 table for diagnostic test evaluation.

Table 6.2 Visualization of test results within a 2 × 2 table.

Table 6.3 Visualization of cells included in the calculation of sensitivity of a diagnostic test in a 2 × 2 table.

Table 6.4 Visualization of cells included in the calculation of specificity of a diagnostic test in a 2 × 2 table.

Table 6.5 Visualization of cells included in the calculation of positive predictive value of a diagnostic test in a 2 × 2 table.

Table 6.6 Visualization of cells included in the calculation of negative predictive value of a diagnostic test in a 2 × 2 table.

Chapter 07

Table 7.1 Example table for analysis of outbreak investigation data to study potential exposure factors.

Table 7.2 Checklist to identify the most likely culprit among potential exposure factors in an outbreak.

Table 7.3 Table for analysis of outbreak investigation data to study potential exposure factors for cases of pulpy feces in a military dog kennel in Germany.

Table 7.4 Checklist to identify the most likely culprit of an outbreak of pulpy feces in a military dog kennel in Germany.

List of Illustrations

Chapter 01

Figure 1.1 Distribution (frequency [no.]) of subjective hip scores for dysplasia using two different definitions.

Figure 1.2 Distribution of isolation of staphylococcal species defined via phenotypic or genotypic methods.

Figure 1.3 Lesion severity score description for a study on gastric lesions in pleasure horses.

Figure 1.4 Epidemic curves: point-source (top) and propagated (bottom).

Figure 1.5 Proportion of whelpings by age group in a study on Boxers.

Figure 1.6 Description of denominators used for the calculation of incidence of vaccine-induced sarcomas in cats.

Figure 1.7 Graphic representation of prevalence calculation (Example A).

Figure 1.8 Graphic representation of prevalence calculation (Example B).

Figure 1.9 Graphic representation of incidence calculation (Example C, notice the altered colors).

Figure 1.10 Graphic representation of incidence calculation (Example D).

Figure 1.11 Venn diagram for the representation of specific disease measurements.

Chapter 02

Figure 2.1 Changes in pain signs in dogs with hip dysplasia after treatment with gold bead implantation.

Figure 2.2 Comparison of outcomes in a study of diet effect on reproduction.

Figure 2.3 Effect of number of intakes on improvement in live-release rate in US animal shelters

Figure 2.4 Comparison of risk of strongyle infection in three facility types and across three European countries.

Figure 2.5 Abstract of a study on the effect of acupuncture on wound healing in dogs

Figure 2.6 Summary of a study on survival in foals with septic arthritis

Figure 2.7 Summary of a study about treatment regimen options against Cheyletiella infestation in rabbits.

Figure 2.8 Example of the use of survival analysis to compare time to a negative event that is not death. In this example, the event is hernia formation after colic surgery in horses that had wound suppuration or not

Figure 2.9 Example of the use of survival analysis to compare time to a positive event. In this example, the event is wound healing after 3 different treatment options: LHP©, cream (1% hydrogen peroxide); P, petrolatum; or U, untreated

Figure 2.10 Graphic representation of the decision flow for determining the appropriate statistical comparison of common veterinary studied variables

Figure 2.11 Abstract of a study on tylosin-responsive diarrhea in dogs

Figure 2.12 Diagram of the udder of a dairy cow (ventral view).

Figure 2.13 Risk factors for postoperative complications in 311 horses recovering from colic surgery. EFE, epiploic foramen entrapment; LCT, large colon torsion, PCV, packed cell volume.

Figure 2.14 Sample size (n), prevalence (% and 95% CI), and intensity of parasitation (average and 90% CI) among wild boars in Spain. CI, confidence interval

Figure 2.15 Meta-analysis of the association of serum alkaline phosphatase and survival time in dogs with appendicular cancer

Figure 2.16 Comparison of pain perception changes after gold bead implantation during a blinded study and when owners were not blinded

Figure 2.17 Univariate analysis of the effect of different factors on the efficacy of rabies vaccination in dogs

Figure 2.18 Multivariate analysis of the effect of different factors on the efficacy of rabies vaccination in dogs

Chapter 03

Figure 3.1 Summary of a review paper.

Figure 3.2 Summary of an original study.

Figure 3.3 Summary of a case report paper

Figure 3.4 Summary of an opinion paper.

Figure 3.5 Summary of a white paper.

Figure 3.6 Table of a review paper on feline epilepsy showing the references used for proving the validity of specific statements, in this case possible adverse effects of oral antiepileptic treatments for cats.

Figure 3.7 Summary of an original study.

Figure 3.8 Summary of an original study (nonstructured abstract).

Figure 3.9 Misrepresented data.

Figure 3.10 Appropriate data presentation.

Figure 3.11 Effect of color on data presentation leading to possible misinterpretation.

Figure 3.12 Effect of color on data presentation helping toward correct interpretation.

Figure 3.13 Nominal data presentation.

Figure 3.14 Proportional data presentation.

Figure 3.15 Use of error bars for the representation of the standard error of the mean.

Figure 3.16 Behavioral conditions associated with early gonadectomy in 1659 dogs.

Chapter 04

Figure 4.1 Types of study designs according to different characteristics.

Figure 4.2 Comparison of flow of information in prospective and retrospective studies.

Figure 4.3 Comparison of diets in cats with diabetes mellitus and age-matched controls

Figure 4.4 Extract of a survey on dystocia in Boxers

Figure 4.5 Experimental protocol for a study of gastric ulcers in race horses

Figure 4.6 Incidence risk of vomiting in dogs in different observational periods in a cohort study

Figure 4.7 Schematic representation of the study design of a clinical trial of the effect of tylosin on diarrhea in dogs

Figure 4.8 Schematic representation of the study design and timeline of a clinical trial of the effect of topical adelmidrol on skin health in dogs

Chapter 05

Figure 5.1 Age distribution of 70 whelping Boxers that needed veterinary treatment

Figure 5.2 Change in risk of vaccine-associated tumors in cats according to the number of vaccines received

Figure 5.3 Comparison of viremia observed in cats vaccinated against feline leukemia and control cats

Figure 5.4 Comparison of tumors observed in vaccination sites versus other locations in cats

Figure 5.5 Effects of sexual maturity (number of estrous cycles) prior to spaying on the risk of developing mammary cancer in dogs.

Chapter 06

Figure 6.1 Graphical representation of accuracy and precision of a diagnostic test.

Figure 6.2 Partial chemistry panel of a 13-year-old intact male dog.

Figure 6.3 Results of a study on variability of laboratory results on serum creatinine concentrations in dogs.

Figure 6.4 Comparison of discrimination ability between two diagnostic tests: one with good discrimination (top) and one with not so good discrimination (bottom).

Figure 6.5 Identification of data needed to calculate the sensitivity of a new rapid test developed for the diagnosis of rabies in dog saliva.

Figure 6.6 Identification of data needed to calculate the specificity of a new rapid test developed for the diagnosis of rabies in dog saliva.

Figure 6.7 Identification of data needed to calculate the positive predictive value of a new rapid test developed for the diagnosis of rabies in dog saliva.

Figure 6.8 Identification of data needed to calculate the negative predictive value of a new rapid test developed for the diagnosis of rabies in dog saliva.

Chapter 07

Figure 7.1 Sketch of the layout of a horse farm that experienced an outbreak of equine herpes virus-1.

Figure 7.2 Sketch of the layout of a horse farm that experienced an outbreak of equine herpes virus-1 (EHV-1), marking the barns in which EHV-1 cases were identified.

Figure 7.3 Epidemic curves: point-source (top) and propagated (bottom).

Figure 7.4 Histogram of cases in an outbreak on a dairy farm. On the graph on the top, the case definition was a dead cow, while on the graph on the bottom, the case definition was a cow that went down, did not respond to treatment, and died.

Figure 7.5 Characteristics of dogs from a German military base from which Salmonella Montevideo (M) and Salmonella Give (G) were isolated during an outbreak.

Practical Clinical Epidemiology for the Veterinarian

Aurora Villarroel

This edition first published 2015 © 2015 by John Wiley & Sons, Inc

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