HSC 404, Final Exam
What are the criteria for something to be a confounder?
-Be a risk factor for the disease. Be associated with the exposure. Not be an intermediate step in the causal path between exposure and disease.
What are the three types of prevention strategies for confounding?
-Randomization -Restriction (ex: trying to control age/sex by only allowing 21 y/o females as test subjects) -Matching
What factors comprise the epidemiological triangle?
-agent -host -environment
Examples of social incongruity include:
-discrepancy between parents in social status -discrepancy between generations, e.g., fathers and sons -changes from rural to urban residence
An epidemiological experiment is performed in which one group is exposed to a suspected factor and the other is not. All individuals with an odd hospital admission number are assigned to the second group. The main purpose of this procedure is to:
-improve the likelihood that the two groups will be comparable with regard to know and unknown confounding factors
A case-control study was conducted to determine if using antihistamines around the time of conception increased the risk of birth defects in the offspring. No personal interviews were conducted regarding the subjects' antihistamine use. Instead, women were considered exposed if computerized pharmacy records from their health maintenance organization indicated that they had filled at least one prescription for antihistamines within 500 days before the birth of the child. What type of information bias is this susceptible to?
-misclassification bias (non-differential)
When assessing a positive relationship between alcohol consumption and oral cancer using a case-control study, increasing the sample size of the study will result in: -a lower p value -a greater odds ratio -a smaller 95% confidence interval -a higher disease prevalence
-none of the above
What are the characteristics of a good screening test?
-simple -rapid -inexpensive -safe -acceptable
According to The Association of Schools of Public Health, competencies in epidemiology to be achieved by Master of Public Health degree candidates in public health include:
-socioeconomic stratification -social networks -discrimination -work demands
Sociocultural influences on health include:
-specific behaviors associated with daily living -mediation of stress exposure -health services utilization
The most important methodological problems in the measurement of life events are:
-subject's recall ability -reliability of measurement -memory biases
In a survey which uses lay interviewers to interview one person about his or her health and the health of household members, the sources of error include:
-the person with disease has had no symptoms and is not aware of the disease -the respondent provides the information but the interviewer doesn't record it or records it incorrectly -the interviewer doesn't ask the questions that he or she is instructed to ask, or asks them incorrectly -the person has had symptoms and has had medical attention but does not know the name of the disease
The population etiologic fraction is a measure of the proportion of the disease rate in a population attributable to the exposure of interest. This measure of effect is influenced by:
-the relative risk of the disease in exposed individuals versus unexposed individuals AND -the prevalence of the exposure in the population
Surgeons at hospital X report that the mortality rate at the end of a 1-year follow-up after new coronary bypass procedure is 15%. At hospital Y, the surgeons report a 1-year mortality rate of 8% after the same procedure. Before concluding that the surgeons of hospital Y are superior, what possible confounding factors should be examined?
-the severity (stage) of disease of the patients at the two hospitals at baseline -the start of the one-year follow-up at both hospitals (after operation vs after discharge) -differences in postoperative care at the two hospitals -equality of follow-up for mortality
Which is NOT a method for controlling the effects of confounding in epidemiological studies?
Blinding
POWERPOINTS/CLASSROOM ACTIVITIES TO REVIEW
CHAPTER 10 AND 11
What are some validity types?
Content Criterion-referenced (Predictive-how often it will correctly predict disease- or Concurrent-how much other measures agree with the result) Construct (how much it agrees with the theoretical concept being evaluated)
Which of the following statements describes the person-environment fit model?
Goodness of fit between the characteristics of the person and environment
A double-blind study of a vaccine is one in which:
Neither observers nor subjects know which subject receives the vaccine and which receives a placebo
A study of the relationship between exercise and heart attacks is conducted among men who do not smoke. Is gender a confounder in this study?
No because there is no variation
Cataracts of the eye may be difficult to diagnose, especially in the early stages. In a study of the reliability of their diagnoses, two physicians each examined the same 1000 eyes, without knowing the other's diagnoses. Each physician found 100 eyes with cataracts. Does this mean the diagnoses are reliable?
No, not unless it was the SAME 100 eyes that they diagnosed.
An attributable-risk percent of 80% was calculated for the association between smoking and lung cancer death. The best interpretation of this statistic would be:
Of those dying of lung cancer who smoke, 80% of those deaths are attributed to their smoking, assuming a causal association exists.
What best defines specificity?
Proportion of people without the disease who have a negative test
What are some reliability types?
Repeated measurements Internal consistency Interjudge
The strategy which is NOT aimed at reducing selection bias is:
Standardized protocol for structured interviews
What are the two types of analysis strategies for omitting confounders?
Stratification (analyses performed to evaluate the effect of an exposure within levels of the confounder) Multivariate techniques (use computers to construct mathematical models that describe simultaneously the influence of exposure and other factors)
What is publication bias?
Studies with positive results are more likely to be published than studies with negative results, and to be published more quickly.
You are planning a case-control study of lung cancer to test the hypothesis that vegetable consumption is protective against lung cancer. Would you match on smoking?
Yes, because it is a risk factor
A follow-up study was conducted on 3000 military troops deployed at an atomic test site in Nevada to detect the occurrence of leukemia. A total 1870 people were successfully traced by investigators, and 443 contacted the investigators on their own as a result of publicity about the study. 4 cases of leukemia occurred among the 1870 people traced, and an additional 4 occurred among those individuals who contacted investigators on their own. Could this be subject to bias?
Yes, because people had motive to come forward
What is validity?
accuracy
Lead time bias is best described as:
an apparently longer survival time among persons identified during a screening program because they were identified at an earlier stage of their disease
What is a good description of a stressful life event?
an occurrence that might cause readjustments in people's activities
If it is accepted than an observed association is a causal one, an estimate of the impact that a successful preventative program might have, can be derived from:
attributable risk
Several studies have found that approximately 85% of cases of lung cancer are due to cigarette smoking. This is an example of:
attributable risk
The purpose of a double-blind study is to:
avoid observer and interviewee bias
Selection bias is most likely to occur in:
both retrospective cohort studies and case control studies
A person with an inaparent infection:
can transmit the infection to others
Recall bias is most likely to occur in:
case control studies
What study design is most likely to suffer from bias due to recall, interviewer?
case-control
What study design is most likely to suffer from bias due to healthy worker effect?
cohort studies
What study design is most likely to suffer from bias due to loss to follow-up?
cohort studies
The type A behavior pattern is hypothesized to be a risk factor for:
coronary heart disease
A test that determines whether disease is actually present is a:
diagnostic test
The CDC published an article concerning the high rate of foot fungal disease in New Orleans. The article explains that there has been a high rate of foot fungal disease in New Orleans for decades. Foot fungal disease in New Orleans is best described as:
endemic
Selective screening involves applying the screening test to:
high-risk groups
How can one reduce bias due to loss to follow-up?
incentives
The degree of agreement among several trained experts refers to:
inter-judge reliability
You are investigating the role of physical activity in heart disease and suggest that physical activity protects against having a heart attack. While presenting these data to your colleagues, someone asks if you could have thought about confounders such as factor X. This factor X could have confounded your interpretation of the data if it:
is a factor associated with physical activity and heart disease
What type of bias? Difference in time between the date of diagnosis with screening and the date of diagnosis without screening, which, if counted in the survival time of patients, will give a misleading picture of the benefits of treatment.
lead time bias
What type of bias? Slow-progressing cases of disease with a better prognosis are more likely to be identified than faster-progressing cases of disease with a poorer prognosis. Thus, cases diagnosed through screening tend to have a better prognosis than the average of all cases.
length bias
A new blood test has been developed to screen for disease Z. Researchers establish 50 units as cut point above which a test is considered positive and thereby indicative of disease. The test manufacturers determine that the test's sensitivity is unacceptably low. However, the manufacturers are not concerned with the specificity and do not want the cost of the test to rise. How can they improve the sensitivity of the test?
lower the cut point below 50 units
Dr.s Poke and Jab (2014) conducted an employee health program that used 5 screening tests at the same time to detect diseases among workers. Which type of program is this?
multiphasic screening
A cohort study of the risk of liver cirrhosis among female alcoholics is done. Incidence rates of cirrhosis among alcoholic women are compared with those among nonalcoholic women. Nonalcoholics are individually matched to alcoholics on month and year basis. Is age a confounder?
no
How can one reduce bias due to healthy worker effect?
obtain controls from the same work environment as cases
What type of bias? Screening identifies an illness that would not have shown clinical signs before death from other causes.
over-diagnosis bias (won't affect their life until death, so it doesn't matter or benefit them to be diagnosed)
The site where a disease agent enters the body is the:
portal of entry
What is reliability?
precision
What measure is conditioned on having a positive test?
predictive value positive
How can one reduce bias due to recall, interviewer?
refer to medical records containing exposure information if they exist
Screening for a disease involves which type of prevention?
secondary
In a study to determine the incidence of a chronic disease, 150 people were examined at the end of a 3-year period. Twelve cases were found, giving an incidence rate of 8%. Fifty other members of the initial cohort could not be examined; 20 of these 50 could not be examined because they died. What is the source of bias?
selection bias
What type of bias? The screening test looks better than it actually is, because younger, healthier people are more likely to get the test
selection bias
In a study to determine the incidence of chronic disease, 150 people were examined at the end of a three-year period. Twelve cases were found, giving a cumulative risk of 8%. Fifty other members of the initial cohort could not be examined; 20 of these 50 could not be examined because they died. Which source of bias may have affected the study?
selection bias: survival bias
Personal behavior and lifestyle factors in health do NOT include:
social support
Selye's concept of the general adaptation syndrome did NOT include:
stage of recovery
What is sensitivity?
the ability of the test to identify correctly all screened individuals who actually have the disease
What is specificity?
the ability of the test to identify only non-diseased individuals who actually do not have the disease
The public health officer from Long Beach complains to you about the dreaded Pacific Pox. The health officer says, "If people catch the Pox, they suddenly get the urge to dance in the sand and fall dead on the beach within the hour." There are no survivors to interview, so you deduce:
the case fatality rate of the Pox must be high
In a RATIO...
the numerator is NOT part of the denominator
A new antibody test detects serum antibodies against virus X (sensitivity 99%, specificity 90%). When applied in a group of hospitalized patients diagnosed as having virus X infections, the test is found to have a positive predictive value of 30%. What best explains this difference between the positive predictive values?
the prevalence of virus X infection is higher among the hospital patients than among blood donors
What is negative predictive value?
the proportion of individuals screened negative by the test who do not have the disease
What is positive predictive value?
the proportion of individuals screened positive by the test who actually have the disease
Screening measures CANNOT be: (reliability & validity)
unreliable but valid
With respect to a hypothetical rabies investigation conducted among veterinary workers (Dr. Spot, 2003) researchers found that rabies was almost always fatal. This finding refers to:
virulence
What is misclassification bias?
when information is not collected or database-d accurately (ex: exposed logged as not exposed)
A case-control study of the relationship between cigarette smoking and pancreatic cancer is done. Coffee drinking is associated with smoking and is a risk factor for pancreatic cancer among both smokers and nonsmokers. Is coffee drinking a confounder?
yes
A study of the relationship between contact lens use and the risk of eye ulcers is done. The crude relative risk is 3.0 and the age-adjusted relative risk is 1.5. Is age a confounder?
yes
