Types of Research Studies Flashcards
1
Q
Why appraise?
A
- many poor quality studies get published even in reputable journals
- conclusions can be formulated based on weak or even non-existent data
- “publication pressure” has resulted in “predatory journals” which often publish w/ v weak peer review policies
2
Q
What is predatory publishing?
A
- open access publishing business model (not all open access journals are predatory)
- charges excessive publication fees to authors
- lack of peer review/ editorial oversight
- may mimic the journal name of a legitimate journal (hijacked journals)
- number of articles published by predatory journals spiked from 53,000 in 2010 to 420,000 in 2014 (8000 active journals)
3
Q
What was the Bohannon Experiment?
A
- Dr. John Bohannon, correspondent for Science, submitted a purposefully flawed scientific paper w/ meaningless results to 304 suspect journals
- responsible peer review process would have promptly rejected
- half of the journals accepted it
4
Q
What are 4 Qs to ask about papers you find related to your clinical Q?
A
- does the paper have the right study design to answer my clinical Q? (if it wasnt a randomized controlled clinical trial, should it have been?)
- which level of evidence does the paper provide?
- is the quality of the paper good enough to help me answer my particular question?
- is the paper relevant to my clinical Q, my population, or patient?
5
Q
What are primary research studies?
A
- case reports
- case series
- observational studies (cohort, case-control, cross-sectional)
diagnostic test validity studies - experimental studies
- clinical trials
6
Q
What are secondary research studies?
A
- reviews (narrative reviews, scoping reviews, evidence based practice guidelines, systematic reviews, meta-analysis)
- economic analyses (partial budgets, decision analysis)
7
Q
What is a case report?
A
- descriptive report of unique or interesting case (“story”)
- may ID a new or unique disease syndrome (“early warning system” - ex: Bo spongiform encephalopathy)
- cannot make any conclusions regarding efficacy of treatment
- “expert opinion” on how to handle this specific type of case
8
Q
What is a case series?
A
- description of the presentation, Dx, treatment, & outcome of a grp of animals w/ same disease
- there are no disease-free animals for comparison
- any differences in treatment or management have not been allocated (these may be due to O’s preferences or individ vet decisions)
- may allow for more description of manifestations of disease & prognosis
9
Q
What are surveys/observational studies?
A
- usually involves obtaining a random sample from a population to obtain an unbiased estimate of the variable of interest
- important application is often to determine prevalence of disease or if a disease is present @ all
- available study populations may not always be representative of true target population
- if all animals in a population are investigated, then the survey is a “census”
10
Q
Census vs survey?
A
A census includes all of a study population and the measurement is called a parameter (true value of characteristic being measured), while a survey looks at a randomized sample of the study population and its measurement is called a statistic (estimate of parameter)
11
Q
What are the benefits and downsides to observational studies?
A
- researcher can study a sp of interest in its natural environment
- can examine a number of hypotheses that might be difficult to examine in an experimental model
- can study rare events in large populations
- harder to control for confounding variables
- harder to make casual associations
12
Q
What are the goals of observational studies?
A
- measure disease frequency (quantify disease - prevalence/incidence)
- assess distribution of a disease (who is getting disease? where is it occurring? when is it occurring? (orienting disease by animal, space, & time))
- identify determinants of disease (risk factors; Are exposure & disease linked?)
13
Q
What are the 2 directions to data gathering?
A
- prospective studies
- retrospective studies
14
Q
What is a prospective study?
A
- looking forward & getting new data after the start of the study
- clinical trials, experiments, cohort studies must be prospective
15
Q
what is a retrospective study?
A
- looking backward & using data that had already been collected
- case-control studies are retrospective
16
Q
What are the types of observational studies?
A
- cross-sectional studies (longitudinal studies)
- case control studies
- cohort studies
17
Q
What is a cross-sectional study?
A
- sample population is selected randomly or sometimes by convenience WITH NO PRIOR KNOWLEDGE ABOUT EXPOSURE OR DISEASE STATUS
- sample population is examined @ 1 point in time (usually)
- each sampling unit is assessed for the factor(s) of interest & the outcome of interest during a “snapshot in time” (best used for chronic diseases or diseases w/ permanent outcomes)
18
Q
What is a longitudinal study?
A
simply cross-sectional studies that follow the sample population over time to assess for various outcomes (allows us to calculate incidence)
19
Q
What are the disadvantages of cross-sectional studies?
A
- weakest observational design (it measures only prevalence, not incidence of disease)
- the temporal sequence of exposure & effect may be difficult or impossible to determine
- usually dont know when disease occurred
- rare events are a problem
- quickly emerging diseases are difficult to study in this fashion
20
Q
What are the subsets in a population in a cross-sectional study?
A
- risk factor & disease; risk factor & no disease; no risk factor & disease; and no risk factor & no disease
- dont know which grp sample belongs to when picking it, but then will ask these Qs
21
Q
What are some sample Qs answered by cross-sectional studies & surveys?
A
- what is the prevalence of Johnes disease in beef cows in Canada?
- what biosecurity practices do poultry operations in the Fraser Valley employ?
- what % of Ca are tested for heartworm in SK?
- do sheep w/ titres to maedi-visna tend to weigh less?
22
Q
What is a case-control study?
A
- separate samples of animals/hers w/ & w/o outcome of interest (often a disease) are selected & these 2 grps are then assessed for exposure to the factor of interest & compared (sour gas ex: select farms w/ & w/o repro failure & then assess these herds for exposure to sour gas)
- easy to perform but prone to more biases
- usually retrospective in nature
- good for rare or acute diseases
23
Q
What are the strengths of case-control studies?
A
- less expensive & time consuming
- efficient for studying rare diseases
24
Q
What are the limits of case-control studies?
A
- inappropriate when disease outcome for a specific exposure is not known @ start of study
- exposure measurements taken after disease occurrence
- disease status can influence selection of subjects
25
Q
What biases are there in case control studies?
A
- sampling bias (bias in selection of cases & controls)
- measurement bias (retrospective nature of ID of exposure to risk factors)
- recall bias
- avoid using data recorded prior to outcome occurring
- use of blinding so that observers & study subjects dont know the case-control status & risk factors being studied
26
Q
What are 4 strategies for control selection?
A
- hospital/clinic based control
- matching
- population based sample of controls
- 2 or more control grps
27
Q
What are examples of Qs answered by case control studies?
A
- are Ca w/ Cryptococcus more likely to have spent lots of time outdoors?
- environmental tobacco smoke & risk of malignant lymphoma in pet cats
- associations of viral & mycoplasmal antibody titres w/ respiratory disease & weight gain in feedlot calves
28
Q
What is a cohort study?
A
- 2 samples of subjects are selected on basis of their exposure to some risk factor
- the subjects are then followed through time for a predetermined period to determine the outcome of interest (the disease)
- less prone to biases
- important to ensure validity of exposure, have equal follow-up, & accurate disease diagnosis
- an observational study design comparing individuals w/ a known risk factor or exposure w/ others w/o the risk factor or exposure
- looking for a difference in the risk (incidence) of a disease over time
- best observational design
- date usually collected prospectively
29
Q
Strengths of a cohort study?
A
- exposure status determined before disease detection
- subjects selected before disease detection
- can study several outcomes for each exposure
30
Q
What are the limitations of a cohort study?
A
- expensive & time consuming
- inefficient for rare diseases or diseases w/ long latency
- loss to follow up can be a major prob
31
Q
Which kinds of Qs are answered by cohort studies?
A
- are farms next to sour gas wells more likely to see higher rates of reproductive failure in their cow herds?
- does smoking cause lung cancer?
- does annual vaccinations of Fe cause fibrosarcoma?
32
Q
What is an experimental study?
A
- study in which a maneuver is performed on an animal in a controlled & artificial surrounding
- often disease is artificially created or induced
- may use lab sp as a model for another sp
- similar to clinical trials in that 2 or more interventions are usually compared
33
Q
What is a clinical trial?
A
- interventions ex: drug treatments or surgical techniques, etc. are given to grps of patients & they are followed up to see what happens to them
- comparison or control grp is used in parallel (parallel arm trial)
- treatments are randomly allocated
- patients used are not in a controlled environment (disease occurs naturally, not induced)
34
Q
what is the experimental design of a laboratory experiment?
A
- comparing 2 or more different interventions
- under carefully controlled environmental conditions
- often involve “artificial infectious challenge”
- may utilize a lab animal sp
35
Q
what is the experimental design of a clinical trial?
A
- any planned experiment involving human or animal subjects designed to assess the effectiveness of 1 or more treatments or preventative measures
36
Q
What is a RCCT?
A
- randomized controlled clinical trial
- controlled means that the experimental subjects receive a new treatment & are compared against other subjects (controls) who receive either a placebo or a standard treatment
- randomized refers to the method of assignment of subjects to treatment & control grps to minimize “bias”
37
Q
what kind of Qs answered by clinical trials?
A
- is Nuflor more effective than Micotil in treating Bo resp disease?
- are omega 3 FAs beneficial in the treatment of pruritis in Ca?
- which of 2 surgical techniques gives a better rate of recovery?
38
Q
what are the advantages of clinical trials?
A
- can have a v specific hypothesis to examine in a precise patient grp
- easier to control confounding variables (eliminates bias if done well)
- more likely to determine causality (prospective design allows this)
- can still assess sp in natural environment in field trials
- allows for meta-analysis @ a later date
39
Q
what are the disadvantages of clinical trials?
A
- expensive & time consuming (many trials never get done b/c of expense; difficult to perform on rare diseases or events; controlled by lrg pharmaceutical companies, get done in a “cheaper” way by using surrogate end pts)
- possible to introduce hidden “bias” however this is rare if trial is carried out correctly
40
Q
Compare narrative & opinion reviews:
A
- traditional review papers
- aim is to review the literature & give advice
- if no explicit mention of an organized literature search, then paper is probably an “opinion article”
- if the literature search is not comprehensive or systematic, then this would be considered a “narrative review”
41
Q
What is a narrative review?
A
- tend to cover a subset of studies based on availability or author selection
- can introduce an element of “selection bias”
- can be informative but not as robust as systemic reviews
42
Q
What is a scoping review?
A
- used to describe the available literature on a topic
- “charting or mapping”
- describes the volume & nature of the existing literature on a topic
- determine the feasibility of conducting a systematic review
- research question for a scoping review is often broader in nature
43
Q
What is a systematic review?
A
- standardized & rigorous methodologies to review all scientific literature for a particular clinical Q (PICO)
- attempts to minimize bias
- comprehensive & systematic literature search
- identify, appraise, & synthesize all relevant studies on a particular topic
- no combining of data btwn studies
- formally reports search strategies on all sources including “grey literature”
44
Q
What is grey literature?
A
- document types produced on all lvls of gov, academics, business, & industry in print & electronic formats that are protected by intellectual property rights, of sufficient quality to be collected & preserved by libraries & institutional repositories, but not controlled by commercial publishers (where publishing is not the primary activity of the producing body)
ex: conference abstracts, presentations, proceedings, regulatory data, unpublished trial data, gov publications, reports (ex: white papers, working papers, internal documentation), dissertations/theses, patents, & policies & procedures
45
Q
What is a meta-analysis?
A
- applying stats to a systematic review of all clinical trial data
- gives a quantitative summary of the info obtained
- focuses on a COMBINED MEASURE OF TREATMENT EFFECT giving a more precise estimate
- can be useful for estimating relative importance of different factors affecting the outcome of interest
46
Q
Rank the types of studies from strongest to weakest clinical evidence:
A
- meta-analysis/systematic review
- RCCT
- cohort study
- case-control study
- cross-sectional study
- case series
- case report
