Week 5 Epidemiology Flashcards
What are case control studies and cohort studies designed to identify?
Two analytical epidemiological study designs that identify common causes of chronic disease such as smoking, ionizing radiation and hep b and high blood pressure (book)
What do randomized controlled studies look at? What are some examples?
They access the management, diagnosis, and prognosis of chronic diseases and either confirm or refute the the causes of disease identified in case controlled or cohort studies.
Examples- Polio vaccine, hormone replacement therapy prostate surface antigen screening
What are two major study design types?
What are some examples?
Interventional- accessing the efficacy of an intervention
Ex- randomized clinical studies and non randomized clinical trails usually longitudinal
Observational- intervention is not under study control, looks at a specific population to identify stuff -> Cross sectional studies, cohort studies, case control studies
What are 3 essential characteristics of epidemiological studies?
1) conducted in humans
2) have control group or comparison
3) clinically relevant endpoints are evaluated
Name an example of a study that would have a low level of clinical evidence and one that is high?
Low- Animal model
High- Systematic review of randomized controlled studies
What is prevalence? How does it range?
prevalence is the sum of all examined individuals or
sites that exhibit the condition or disease of interest divided by
the sum of the number of individuals or sites examined. The
prevalence can range from 0% (no one has the condition or disease
of interest) to 100% (everyone has the condition or disease of
interest).
What is risk?
risk is the probability that an individual or a site will develop
a particular condition or disease during follow-up. The risk for a
condition or a disease is a number that ranges between 0% and
100%. Should be accompanied by a specific period of time!
What is odds? How does it range?
odds for an event is the probability that an event occurred
divided by the probability that an event did not occur. Whereas
probability is a value that has to range between 0 and 1, odds values
range from 0 to infinity.
What is incidence rate? When would it be 0 and when infinity?
Incidence rates are an alternative measure to describe disease
occurrence. In clinical trials or epidemiology, the rate reflects
the number of disease occurrences per person-time or site-time. It implies an element of time-denominator is time!!
Zero if no new disease onsets during
the study period, the incidence rate is 0. When every person observed dies instantaneously at the start of the study (and thus the sum of the time periods is 0), then the incidence rate is infinity.
Whats the difference between prevalence and incidence?
prevalence is the proportion of a population which has
a condition at a given point in time (e.g., 9% of the US population had
severe periodontitis in the 2009-2010 NHANES survey), while incidence
is the probability that a disease will occur in a previously healthy population over a period of time (e.g., the incidence of peri-implantitis for patients with mandibular over-dentures is 17% after 5 years).
Two common measures of gingival inflammation? How are they different?
Gingival Index (GI) and bleeding on probing. gingival index is a categorical index that assesses the severity of gingival
inflammation on a scale from 0 to 3. On the other hand, BOP is a binary index (Yes/No) that determines whether a site is bleeding on probing
or not
What are 3 Commonly used measures of periodontal tissue destruction?
mean probing depth, mean attachment loss, and mean recession
level
Whats the difference between sensitivity and specificity? What are the “downsides” of each one?
Sensitivity is defined as the number of diseased patients who are correctly identified as having disease—that is, the diagnostic marker leads to a minimum number of false negative diagnoses.
Specificity is defined as the number of healthy persons who are correctly determined to not have the disease—that is, the diagnostic marker leads to a minimum number of false positive diagnoses.
What’s epidemiology?
What are Case–control studies? What kind of design are they? What is the primary goal of it? give an example of a case-control study?
Case–control studies are typically referred to as outcome-based study designs. Follow two groups: case and control and compare the difference. Randomized case control study is the gold standard.
The primary goal of a case–control study is to find out what past exposures or factors are different between patients with a disease versus those without the disease.
EG: Destructive periodontal disease, risk factor-Smoking
What is a Periodontal Index? Who developed it?
Russel, 1956. scored
the supporting tissues for each tooth in the mouth according to a
progressive scale that gives little weight to gingival inflammation
and relatively great weight to advanced periodontal disease
What does endemic mean?
What are the epidemiological measures of disease?
Prevalence and incidence. Incidence has a time in a denominator
What is epidemic?
What are the two main epidemiologic study designs?
Analytic and intervention studies
Which of the two cohort studies more powerful- retrospective or prospective?
Prospective. Can control the intervention. For rare disease or with funds limited can do retrospective
How do we calculate Sensitivity?
Probability that the test will indicate “disease” among those with the disease.
It equals to the True+/(true+ plus false-)
In this case true positive is 400, false negative is 100. The result is 400/(400+100)*100%=80%
How do we calculate specificity?
Specificity is the fraction of those without disease who will have a negative test result:
True negativeD/ (True-D plus False+B)100%= 450/(450+50)100%= 90%
What are odds ratio and how do we calculate it? How Do you interpret the odds ratio?
It’s ratio of the odds that cases were exposed to the odds that controls were expected. Used for cross-sectional studies. Odds ratio= ad/bc=3.33. Odds ratio: More than 1= harmful Effect Less than 1 = protective effect Equals 1 = no association
How is papillary marginal attachment index measured?
At first just a binary on the basis of presence of inflammation: inflammation=1, no inflammation=0.
Later- a scale: for papillary 0-5, for marginal and attachment : 0-3
What is periodontal index?
created by Russel, 1956. Not used anymore
What is a community periodontal index of treatment needs (CPITN)?
Created by WHO in 1977, used for developing countries.
What are the 6 risk factors of periodontal disease?
1) bacterial plaque
2) Smoking
3) systemic disease
4) Age
5) gender
6) race
