Test 1 (EBVM 1-12) Flashcards
What is involved in a PICO?
patient, intervention, comparison, outcome
definition of EBVM
the conscientious and judicious use of the current best evidence in the health care of individuals and populations; integrating individual clinical expertise with the best available external clinical evidence from systematic research
what does EBVM help us do
helps determine which is the BEST approach for the CASE/SITUATION
three main steps of EBVM
-diagnostic process
-treatment alternatives
-disease prevention
what is included in the diagnostic process
diagnostic decisions such as tests and their performance
what is included in treatment alternatives
treatment decisions, interventions and strength of evidence associated with them
what is included in disease prevention
preventative health decisions, herd health and wellness, and causation
what are the 6 steps in the diagnostic process
- presenting complaint
- history
- general inspection
- routine physical exam
- clinical or other tests
- diagnosis!
four LDA treatment options
-right paramedian abomasopexy
-omentopexy
-bar suture (toggle pin) abomasopexy
-roll and treat medically
what are the two highest pieces of evidence
systematic reviews and meta-analysis
three types of observational studies
cross sectional, case control and cohort studies
two type sof experimental studies
experiements and clinical trials (RCTs)
both observational studies and experimental studies are ____ _____ studies
hypothesis testing
what two study types have temporal sequence established
RCTs and cohort studies
what two study types have unknown temporal relationships
cross sectional and case control
advantages of cohort studies (3)
-generally preferred over case control studies bc the are statistically more reliable
-compared to case-control they can establish the timing and sequence of events
-in prospective studies, data collection can be standardized, as opposed to retrospective studies which use historical records
disadvantages of cohort studies (4)
-blinding within the studies is difficult. identifying a matched control group to minimize other variables can also be difficult
-cohort studies arent as reliable as RCTs as the two groups of animals may differ in ways other than simply in respect of the variable under study
-can take a long time to complete and there might be a loss of participants
-not useful for rare diseases as it would be difficult to recruit sufficient patients
what happens in a cohort study
animals exposed to a causal factor are followed over time and compared with another group of animals which are not exposed to that factor.
what are results normally expressed as in a cohort study
risk ratio
can absolute risk be determined in a cohort study
yes
what happens in a case control study
animals which have developed a disease or condition are identified, and their exposure to suspected causal or risk factors is compared with that of a control group which do not have that disease/condition. information regarding exposure is historical
what are results normally expressed as in a case control study
odds ratios
can absolute risk be determined in a case control study
no
advantages of a case control study (4)
-quick to perform and dont require special methods to conduct
-generally inexpensive and may be the only way in which rare conditions or those with a protracted incubation period can realistically be studied
-can be used to evaluate interventions as well as associations
-useful for formulating hypotheses that can be tested using study designs higher up in the hierarchy such as cohorts and RCTs
disadvantages of a case control study (3)
-less reliable than RCTs or cohort studies as it is difficult to match the control group and eliminate confounding variables
-not possible to calculate true incidence/prevalence and relative risk
-data is collected retrospectively and elements may be missing or of poor quality
what happens in a RCT
study design of choice for answering questions about the effectiveness of different treatments. a search for evidence from studies of this design should be a priority when asking questions about therapies
advantages of RCT (3)
-random allocation of animals into study groups reduces the risk of bias and is the most powerful method of eliminating known and unknown confounding variables
-the RCT is the most powerful study design for data collection
-the study design increases the probability that the differences between the study groups can be attributed to the treatment
disadvantages of RCT (2)
-its sometimes not possible to allow for an untreated control group due to the severity of the effects of witholding an effective treatment
-expensive to conduct and relatively rare it vet med
what is “random”
same chance of getting A or B treatment. cant have a sequence
WHAT KIND OF STUDY IS THIS
Cows were blocked by parity and randomly assigned to receive an oral bolus of Ca (42 g of Ca) within 12 h
after calving and a second bolus 12 h later (TRT; n = 51), or no Ca
supplementation (CON; n = 49).
Concentrations in serum of total Ca (tCa), haptoglobin (Hp), and albumin (ALB) were assessed at d 0 (within
12 h postpartum), 0.5 (12 h later), 1, 2, 4, 6, and 8 postpartum; ionized calcium was assessed at d 0, 0.5, 2, and 4, and lipopolysaccharide binding protein (LBP) and serum amyloid A (SAA) were assessed at d 0, 2, and 4.
RCT
WHAT KIND OF STUDY IS THIS
The condition of 640 male dairy calves was recorded and their health deterioration, morbidity, and
mortality evaluated after long-distance transport. Assessments included a health examination, weight estimation, and measure of failed transfer of passive immunity (FTPI). A McNemar Test and logistic regression analysis were used to evaluate the effects of pre-transport condition on subsequent health.
cohort
WHAT KIND OF STUDY IS THIS
The objective of this study was to investigate the relationship between management practices and
antimicrobial use in heifer calves on Canadian dairy farms. Questionnaires on calf management practices, herd characteristics, and calf treatment records were administered on 147 dairy farms in 5 provinces during annual farm visits. Antimicrobial treatment records were collected on each farm from either an electronic herd management system or paper-based records.
cross sectional
WHAT KIND OF STUDY IS THIS
A study was performed to assess risk factors associated with feline ureteral obstruction (UO). Cases were defined as cats with either of the following: (1) ureteral obstruction (ureteroliths: 13/18; unknown: 5/18) confirmed with pyelography; or (2) a creatinine concentration >140 μmol/l with both UO (ureteroliths: 6/10; blood clots: 3/10; pyonephrosis: 1/10) and pyelectasia ⩾5 mm on abdominal ultra sonography. Controls were defined as cats without evidence of UO on history, physical examination and abdominal ultrasound. Age, sex,
breed (domestic shorthair/longhair), diet (predominantly dry, mixed or predominantly moist food), housing
(indoors or mixed) and plasma total calcium were evaluated for their association with UO using multivariable logistic regression.
case control
what are the 14 pieces of information/questions you need answered to be able to trust a study?
- Are you able to define the type of study?
- Clearly stated objectives | Relevance check
- External validity - extrapolation
- Inclusions and exclusions
- Group definition & allocation
- Procedures appropriately defined & applied
- Equal scrutiny of ALL groups (“blinding”)
- Outcomes defined & appropriate
- Biases / confounders dealt with
- Statistical Analysis – appropriate tools
- Statistical Analysis – proper interpretation (what’s a P value and 95% Confidence intervals)
- Sample Size determinations based on the outcome of interest
- Clear and Complete Results
- Conclusions appropriate and complete
three types of clinical questions
diagnostic, treatment, preventive
“What is the accuracy of rectal palpation for identifying functional
CL’s in dairy cows?”
what type of clinical question is this
diagnostic
“Is surgical repair superior to confinement & rest in resolving
lameness due to anterior cruciate rupture in large breed dogs?”
what type of clinical question is this
treatment
“How much reduction in morbidity should I expect in beef calves vaccinated with Triangle 9 at arrival in a large feedlot? “
what type of clinical question is this
preventive
“In canines with osteoarthritis does fish oil supplementation improve quality of life parameters?”
whats missing from this clinical question
Population: try to define your
population to reflect any characteristics that might influence
development of OA or response to
treatment. ex. age, comorbidities
Intervention-Comparison: you list fish
oil supplements, but there’ no
comparison Additionally, define your
treatment (dosage, route of administration, frequency, etc)
Outcome: how will you define quality of life? Find an objective measure to help make your clinical decision.
“Which surgical intervention (tibial-plateau-leveling osteotomy (TPLO) vs. lateral fabellar suture stabilization (LFSS) leads to a reduced osteoarthritis (OA) score in active, young dogs with cranial cruciate ligament rupture?”
whats missing from this clinical question
Outcome: osteoarthritis development is a relevant outcome, but defining a time frame would be more specific. Follow up period: Are we wanting to know if the dog develops OA in 3 months? 8 years?
Population: define a breed size, as things like weight/weight bearing
might impact your treatment decisions and outcome
In dogs experiencing dystocia and requiring a C-section, does performing a c-section as opposed to a csection spay affect the survival rate of the puppies?
whats missing from this clinical question
Other maternal factors that might play a role here? [age? Brachiocephalic phenotype? ]
You may wish to define the period of survival in the puppies. (immediate neonatal period, or further along?)
what are some sources of evidence in practice (5)
-Personal Experience
-Colleagues
-Textbooks, Reviews, CPD meetings
-Practice Records
-Journals (namely peer-reviewed papers)
what are some practice record issues (4)
-Quality
-Completeness
-Case definition
-Follow-up (outcomes & complications)
most practice records were not designed to do what?
evaluate outcomes of procedures
what are three things we need to consider if we are using practice records
-incidence/prevalence of a disease = need a case definition
-probability of success = need follow up and outcomes
-complications = need to be recorded
how do we define a new case? (4)
-distinct case? is this the 1st vs new vs recurrent
-who is at risk? (parity, DIM, etc)
-how long are they at risk?
-how do we define a cure (outcome)?
what are the biggest issues in practice around finding the answer?
access and ability to find the right articles
what are three databases for animal health
CAB direct, pubmed/medline, agricola
three types of descriptive papers
case report, case series, review papers
what is different between descriptive papers and explanatory papers
descriptive papers do not have controls or comparisons
features of descriptive papers (6)
-detailed descrption of uncommon diseases
-biased in case selection
-no controls or comparison group
-raise awareness
-generate great questions for future research
-not very useful for decision making
what do we mean by association vs causation
Just because a risk factor and an outcome occur together more commonly than one would expect by chance alone, doesn’t mean that the risk factor CAUSES the outcome!
hills criteria for causation (7)
– Temporal Relationship (Exposure → Outcome)
– Strength of Association (RR or OR)
– Dose-Response
– Biological Plausibility
– Consistency or Repetition
– Rule Out other potential causes
– Reversal
the more of the hills criteria you can include in your search = the stronger the ______ argument
causal
what is the best type of study for rare diseases
case control
what is the best type of study for rare risk factors
cohort
two measures of association
relative risk and odds ratio
what is a measure of association
-measure the magnitude/strength of the relationship between an exposure (E) and outcome (O) as a relative effect
-it is A RATIO of two estimates of disease frequency
what type of studies can be use risk ratio in
cross sectional or cohort studies
what type of studies can be use odds ratio in
all studies
what is the chi square test of independence used for
used to test whether two categorical variables are related to each other
what does a RR = 1 tell us?
there is no association between factor and disease
what does a OR = 1 tell us?
there is no association between factor and disease
what does an OR of less than 1 tell us
strong negative (protective) association
what does an OR of more than1 tell us
strong positive (causal?) association
7 features on the controlled trial checklist that we should apply when reading papers
- Objective and Hypothesis
- Sample size calculation performed for all outcomes of interest
- Random allocation
- Check if randomization worked
- Blinding and placebos
- Effect size of differences between groups
- Survival bias? Other Limitations stated?
what is true prevalence
pre-test probability of disease
what is the positive predictive value
If the test (or clinician) says “Positive”, what’s the probability of that result to be actually positive?”
what is the negative predictive value
If the test (or clinician) says “Negative”, what’s the probability of that result to be actually negative?”
what is a false negative
If the test (or clinician) says “Negative”, but, in reality, the result is “Positive”?”
what makes a good gold standard
Perfectly classifies individuals as Responsive/Diseased or not
why is palpating for a functional CL a common practice (4)
-Palpation alone FOR THIS PURPOSE is not a very good test
-Use all available information to help make the diagnosis
-Palpation is still a very important skill and test
-For other applications can be a very good test
do sensitivity and specificity tend to change when prevalence of disease changes
nope
what changes with the prevalence of disease
-Probability of disease if test positive (PPV)
-Probability of disease if test negative
-Probability of NO disease if test negative (NPV)
10 steps in assessing vaccine efficacy
- has the vaccine been lab and field tested in RCT
- were the control groups concurrent or historical
- how were the trial animals challenged
- was he measure of outcome meaningful
- were the biology and epidemiology of the disease considered
- was the vaccine randomly assigned
- were blinding techniques used to reduce bias
- what other potentially important biases are evident
- how likely was the result a chance finding
- what are the differences between the trial animals and animals in your practice
what is the purpose of vaccines
To prime the immune system so that the animal can better ‘defend’ itself against infection with the agent when it is ‘challenged
what are vaccines
A substance used to stimulate the production of antibodies and provide immunity against one or several diseases, prepared from the AGENT of a disease, its products, or a synthetic substitute, treated to act as an antigen without inducing the disease
what are some desirable outcomes of vaccines
-Fewer animals get sick
-Animals don’t get as sick
-Animals aren’t sick for as long
-Fewer animals die
-The vaccinated animal produces protective antibodies
what type of study is this
Comparison of past histories of animals that have a disease with those in a comparable groups undiseased animals
case control
what type of study is this
Simultaneous classification of a group of animals according to the disease status and a study factor to determine if an association exists
cross sectional
what type of study is this
Most useful for rare outcomes
case control
what type of study is this
Is it not possible to calculate true Incidence/Prevalence and Relative Risk
case control
what type of study is this
Identification of two groups of animals (one group with the factor being studied and one without) and
subsequent follow-up of the groups throughout time to determine if disease develops
cohort
four types of bias to be aware of during critical appraisal
response bias, confounding bias, selection bias, recall bias (information bias)
what are narrative reviews and what questions do we need to ask surrounding them (4)
-Usually written by content experts
-Is there selection bias in identifying and including original research?
(conscious or unconscious?)
-Is there a possibility for information bias? (scientific quality of the primary studies)
-Is there potential for publication bias? (unpublished results?)
-How do we evaluate their utility? Same as for a primary research study!
~~Are the results replicable?
~~Are the conclusions valid?
what are systematic reviews
-A review of a clearly formulated question that uses systematic and explicit methods to identify, select, critically appraise, and summarize relevant research
* Defined steps that are structured and documented, multiple reviewers at each stage
* Risk of bias in primary research studies is assessed to identify any methodological issues to aid in interpretation of results
* Conducted by a review team: should include both content experts and methodological experts
what is the answer to a systematic review question
its a number
what are systematic review methods well described for
-Intervention studies (RCTs)
-Prevalence/incidence/proportion studies
-Diagnostic test accuracy studies
- +/- observational studies
-Methods are well describe
what is a scoping review
-Used to determine the size and nature of an evidence base for a particular topic area
-Differ from standard systematic reviews in that they do not attempt to synthesize the evidence
uses of a scoping review (5)
-Identify gaps in the literature and make recommendations for future research
-Planning primary research or systematic reviews
-Assessing the feasibility of a full systematic review
-NOT appropriate for answering a clinical question
-May be a good first step in determining whether there is enough evidence to justify a full systematic review (or, what interventions for a
topic have specific evidence)
what is the answer to scoping review questions
a list
9 steps for systematic reviews
1.) Define the review question
2.) Develop a review protocol (plan for steps 3-9)
3.) Comprehensive search for studies
4.) Select relevant studies from the search
5.) Collect data from relevant studies
6.) Assess risk of bias in relevant studies
7.) Synthesize the results
8.) Present the results
9.) Interpret the results
what is the most important step in a systematic review
developing the review question
four types of review questions
-prevalence/incidence
-diagnostic test accuracy
-etiology
-intervention
what needs to happen in order to select relevant studies (3)
-Standardized screening forms are made, and each citation is screened independently in duplicate by two
reviewers
-First, titles and abstracts are screened (more rapid)
-Then, full text articles are screened
what is the aim of collecting data from relevant studies
-Aim is to extract data from study results, and characteristics that influence the external validity, internal validity, and limitations of the study
what needs to happen to assess risk of bias in relevant studies
-Specific criteria related to risk of bias will vary by type of review question (eg/ controlled trials, observational studies, prevalence studies, diagnostic test accuracy studies)
-Templates are available for different types of review questions
-Completed independently in duplicate by two reviewers
what are some examples of design features relaed to risk of bias in controlled trials
-Allocation concealment
-Randomization
-Blinding of participants, caregivers, outcome assessors
-Loss to follow up
‘Intention to treat’ vs. ‘per protocol’ analysis
what is a narrative synthesis
a summary of quantitative data when meta-analysis is not feasible or advisable
what is a meta analysis
a statistical combination of data from multiple studies
what is a pairwise meta analysis
a comparison of two treatments (eg/ treatment and control), directly
compared in studies
what is a network meta analysis
a comparison of multiple treatments, compared both directly and indirectly
in studies
what do pairwise meta analysis allow for
Allows for an overall treatment effect, as well as an indication of how much between study variation there
interpretation of I2 in pair wise meta analysis
I2 indicates the amount of heterogeneity - general rule of thumb is 30-50% is moderate, 50-80% is
substantial, >80% is considerable
Heterogeneity can be explored by subgroup analysis and meta-regression, if we captured relevant variables
advantages of systematic reviews and meta analysis (5)
-Answers a targeted question
-Much faster to read one review compared to sifting through thousands of articles
-When conducted well, high level of
reproducibility
-Quality of evidence can be high, when conducted well and evidence included is of high value (low risk of bias)
-Not yet in vet med – but ‘living reviews’ are becoming more common in human health care
limitations of systematic reviews and meta analysis (4)
-Can only be done when there is a body of evidence to synthesize!
-Subject to quality of the included studies (although can identify where this is lacking)
-Some are conducted poorly! (Check
what the question is, did they follow the general framework?)
-Answers a targeted question - may not directly apply to your clinical question
what is control of a disease based on
is based on management/ manipulation of risk factors
infectious vs contagious
Caused by or capable of being communicated by a microorganisms in body tissues – is about the agent
Capable of being transmitted from individual to individual. Communicable – is about the transmission
example of infectious vs contagious agents
Coliform Mastitis vs. Staph aureus Mastitis
how are contagious diseases spread
-Contagious diseases are spread by contact, while infectious diseases are spread by infectious agents
-Contagious is also infectious (contact exposed the host to the infectious agent)
is infectious always contagious
naur
definition of pandemic
a global epidemic
definition of endemic
-Predictable long- term balance between agent & host
-Stability of balance influenced by
environmental & host factors
definition of epidemic
-Gross imbalance between agent & host
-Usually occurs during initial exposure
definition of sporadic
-Agent is present but disease occurs
infrequently and not is readily predictable
necessary vs sufficient
necessary
-must be present to cause disease
-always a component of a sufficient cause
sufficient
-ALWAYS produces disease
-Rarely one single determinant; generally a group of host, agent, and environment factors
-One disease can have several sets of component causes that combine to produce sufficient cause
three approaches to infectious disease control
eliminate
prevent
control
what is the reed frost model
The factors affecting the introduction, survival and/or spread of an agent in a population
three options for eradication of infected animals when eliminating disease
-depopulate = remove all animals
-selective = test and slaughter (requires good screening tests)
-treatment =
scopes of eradication
-Global
-National
-Regional
-Farm
three ways to approach elimination of disease
- Eradication of infected animals
- Immunization of animals at risk
- (A+B) Test & Slaughter and Vaccination –> Disease will ‘die out’
examples when a combination of eradication and vaccination was used to eradicate a disease
-Brucellosis and Foot-and-mouth disease (FMD) eradication regionally
-Rinderpest eradication globally
three ways to approach prevention in infectious disease control
-reduce exposure to agent
-reduce stress on host
-enhance resistance (immune system)
ways to reduce exposure to an agent
- Reduce Animal Contact (contagious)
-BIOSECURITY: Closed vs. Open herds
-No exposure to animals of the same species from outside the herd
-Quarantine additions?
-Is there a downside? yeah, welfare and Naïve Populations
ways to enhance resistance
-Genetics - long term!
-Nutrition – vitamin E and selenium
-Immunization – protective antibodies (Passive or Active)
ways to control infectious disease
-Strategic or Routine Medication
~~A: Metaphylaxis (not prophylaxis)
~~B: Medicated feed
~~C: Fleas
~~D: Heartworm
what is metaphylaxis (control) treatment
Therapeutic levels of antibiotics to treat subclinically diseased animals
what is prophylaxis (prevention) treatment
give to everyone without reason =
Administration of antibiotics to animals at high risk of infectious disease (but without current disease and where there is no known disease in the herd or flock). Prophylaxis is commonly used when environmental conditions or changes portend
increased risk for infection. Examples of such conditions include transport of animals and confining animals to small, crowded spaces
is elimination, prevention or control the best approach to infectious disease control?
it depends on what the risk is
what are the two components that determine risk
probability and magnitude
what three aspects do you need to consider with magnitude
-Magnitude of the problem (distribution)
-Magnitude of the economic impact
-Zoonotic potential
how to determine the magnitude of economic impact
-decreased performance
-treatment costs (drugs and labour)
-unsaleable product (carcass condemnation, drug residues)
-death
-export markets (e.g., consider BSE (rare) vs JD (endemic))
what is biosecurity
Biosecurity is the protection of people, animals and ecological systems against disease and other biological threats.
how is biosecurity achieved
Biosecurity is achieved through systems that aim to protect public health, animal and plant industries, and the environment, from the entry, establishment and spread of unwanted pests and diseases.
what is biocontainment
export of the disease agents beyond the farm that may have an adverse effect on the economy, environment and human health
5 approaches to biosecurity
-increased awareness
-increased risk of disease spread
-increased quantification of disease
-increased public scrutiny
-increased benefit/cost to producers
what is foreign animal disease
A range of biological threats to livestock, poultry, and wildlife that are not normally found in Canada.
Examples: foot-and-mouth disease (FMD) and Schmallenberg virus
why do we care about tracking foreign diseases globally?
-prevent disease from coming
-so we know whats going on
-anything can be brought here
definition of disease surveillance
The continuous investigation of a given population to detect the occurrence of disease for control purposes, which may involve testing a part of the population
what is active surveillance
Initiate an active data collection mechanism
Examples: Testing all down cows for BSE; collecting samples for antimicrobial testing at abattoirs
what is passive surveillance
Use data derived from other sources (Secondary Data)
Examples: Accessing samples/data coming in through diagnostic labs,
public health units, human & veterinary practices
what is the mission of the ontario animal health network
Coordinated preparedness, early detection, and response to animal disease, through sustainable cross-sector networks.
what are the targets of biosecurity
-Introduction of Foreign Animal Diseases (Exotic to country or continent)
– Herd-to-Herd Transmission (Endemic to country or region)
– Animal-to-Animal Transmission (Endemic to the herd)
– Animal-to-Human Transmission (Public Health & Food Safety)
all perils vs targeted biosecurity
all perils biosecurity
-is difficult, not defined
-likely not cost-effective
-may not be maintained
targeted biosecurity
-is possible - focused
-can be cost-effective
-can be maintained
6 steps in a targeted approach
- Identify disease(s) of concern
- Determine current prevalence of disease
- Limit animal movement within and between farms - if necessary test before
- Implement a disease prevention program
- Monitor compliance with program
- Review program annually
5 reasons to control johnes disease
- JD is a production limiting disease
- JD is an infectious disease
- Diagnostic tests for JD are good
- Cost-effective JD control programs work
- Johne’s is probably a zoonotic disease
what is RAMP
Risk Assessment & Management Plan
recommendations from RAMP in terms of johnes disease (10)
- Don’t buy cows…or buy from low risk herds
- Remove calves QUICKLY from maternity area
- Feed MORE colostrum to newborn calves and feed it on time
- Don’t walk through feed bunk or calf pens with dirty boots
- Collect and feed low risk colostrum to calves from high risk cows
- SEPARATE newborn calf from cow
- Don’t feed non-saleable milk to calves
- Don’t use calving pen as the hospital pen
- Re-test herd annually
- Feed low risk milk to calves
what is one health
An approach that recognizes that the health of people is closely connected to the health of animals and our shared environment
what are some challenges of biosecurity related to zoonosis
-Some pathogens cause disease in both animals and humans
-Pathogens that pose greatest risk to people may not cause disease in animals
-Pathogens that make cows sick may or may not be zoonotic or easily transmissible/detectable
steps for managing zoonotic risk
-Prevent infectious disease
-Limit disease spread on & between farms
-Treat or cull sick animals
-Collect meat and milk hygienically
-Pasteurize all dairy products
-Maintain potable water
-Wash hands
what type of study is this
Among the observational studies is the best to argue causation
cohort
what can histophilus somni cause
Can cause an acute, often fatal, septicemic disease involving the respiratory, cardiovascular, musculoskeletal and/or nervous systems
