Medicine Expert Q&A

In 1999 the army of country Z started to collect data from all their recruits.As part of the process,they conducted a full physical examination in which audition was measured and reported as normal hearing,low hearing loss,and severe hearing loss.Unfortunately,5 years later country Z went into a war with country Y.In 2018 a researcher from University U decided to conduct a study in which she investigated the association between hearing loss and suffering a war injury.What type of study design is being illustrated in this example?

A) Case-control study
B) Cross-sectional study
C) Ecologic study
D) Prospective cohort study
E) Retrospective cohort study

What is the most important assumption in this type of analysis? Use the following table to answer the question. Survival of Patients With Metastatic Cancer Z Following Diagnosis
$\begin{array}{llllllll}\begin{array}{l}\text{ Interval }\\ \text{ since }\\ \text{ beginning }\\ \text{ treatment }\\ \text{ (months) }\end{array}& \begin{array}{l}\text{ Alive at }\\ \text{ beginning }\\ \text{ interval }\end{array}& \begin{array}{l}\text{ Died }\\ \text{ during }\\ \text{ interva }\\ 1\end{array}& \begin{array}{l}\text{ Withdre }\\ \text{ whterval }\end{array}& \begin{array}{l}\text{ Effective }\\ \text{ number }\\ \text{ exposed }\\ \text{ to risk of }\\ \text{ dying }\end{array}& \begin{array}{l}\text{ Proporti }\\ \text{ on who }\\ \text{ died }\\ \text{ during }\\ \text{ interval }\end{array}& \begin{array}{l}\text{ Proportion }\\ \text{ who did not }\\ \text{ die during }\\ \text{ interval }\end{array}& \begin{array}{l}\text{ Cumulative }\\ \text{ proportion }\\ \text{ who }\\ \text{ survived }\\ \text{ from }\\ \text{ enrollment }\\ \text{ to end of }\\ \text{ interval }\end{array}\\ x& I_x& d_x& W_x& I_x^{\prime }& q_x& p_x& P_x\\ 1-12& 200& 10& 40& & & & \\ 13-24& 150& 20& 30& & & & \\ 25-36& 100& 30& 20& & & & \\ 37-48& 50& 40& 10& & & & \end{array}$


A) There has been no secular (temporal) change in the effectiveness of treatment or in survivorship over calendar time.
B) The effect of treatment has improved during the period of the study.
C) The survival experience of people who are lost to follow-up is better than the experience of those who are followed up.
D) The survival experience of people who are lost to follow-up is worse than the experience of those who are followed up.
E) An equal number of men and women enrolled each year.

Mr.Patient tested positive for disease X.He went to see Dr.Gordis and asked him what was the probability of truly being sick given the results of the test.To answer that question,Dr.Gordis must know what about the test?

A) Sensitivity
B) Specificity
C) Prevalence
D) Positive predictive value
E) Negative predictive value

Two similar drugs (drug A and drug B) to alleviate back pain were released simultaneously.An investigator decides to test which of the drugs works better.He decides to conduct a trial in which randomly,half of the participants receive drug A for a month while the other half received drug B.After 2 weeks without any medication,participants switch the drug they were receiving (those who received A start taking B,and those who received B start taking A) .What type of study design was illustrated in this example?

A) Cross-sectional study
B) Factorial randomized clinical trial
C) Crossover randomized clinical trial
D) Crossover cohort study
E) Phase II clinical trial

There was a food poisoning outbreak on April 1,2018,at the City Z Food Safety Conference.There were 1,000 people registered for the conference with luncheon,100 volunteers to host attendees,and 50 people who served the luncheon during the conference.Except for 50 people who served the food,all of the participants and volunteers ate the food from the luncheon at the conference on April 1,2018.After an initial outbreak of food poisoning is reported,an epidemiologist sends surveys to all people at risk to investigate the cause.However,only 900 people among those at risk answer the survey.After analysis of 900 survey results,the epidemiologist concludes that the most suspected foods in the outbreak are pepperoni pizza and meatball spaghetti.What is the most suspected food for food poisoning after cross-tabulation? Use the following table to answer the question. Summary of Survey Responses
$$\begin{array}{lll}& \begin{array}{l}\text{ Number of people who }\\ \text{ developed the case definition }\\ \text{ symptoms }\end{array}& \begin{array}{l}\text{ Number of people who ate the }\\ \text{ food }\end{array}\\ \text{ Pepperoni pizza only }& 113& 275\\ \text{ Meatball spaghetti only }& 62& 375\\ \begin{array}{l}\text{ Both pepperoni pizza and }\\ \text{ meatball spaghetti }\end{array}& 57& 150\\ \begin{array}{l}\text{ Neither of pepperoni pizza or }\\ \text{ meatball spaghetti }\end{array}& 10& 100\end{array}$$


A) Pepperoni pizza only
B) Meatball spaghetti only
C) Both pepperoni pizza and meatball spaghetti
D) Neither pepperoni pizza nor meatball spaghetti
E) We cannot determine the cause of food based on this information

An epidemiologist decides to investigate the incidence of diabetes in a population of 300 older adults who live in a nursing home.She visits the nursing home in January 1,2017 and later in December 31 of the same year.She looks into the records of these patients and learns that in her first visit,25 patients had diabetes and 35 in her second visit.What number should be included in the denominator for her calculation of incidence?

A) 10
B) 25
C) 35
D) 300
E) 275

Which of the following statements about specificity is the most accurate?

A) The probability that a diseased person (case) in the population tested will be identified as diseased by the test.
B) The probability that a person without the disease (noncase) in the population tested will be identified as nondiseased by the test.
C) The probability that a person identified as diseased by the test will be a diseased person (case) in the population.
D) The probability that a person identified as nondiseased by the test will be a person without the disease (noncase) in the population.
E) The probability that a diseased person (case) in the population tested will be identified as nondiseased by the test.

The main difference between a cohort study and a randomized trial is that

A) cohort studies are longitudinal and randomized trials are cross-sectional.
B) only clinical trials can evaluate the effect of a drug.
C) randomized trials are experimental and cohort studies are observational.
D) clinical trials are observational and cohort studies are experimental.
E) at the beginning of a clinical trial, participants are free of disease, and cohort studies start with patients with a disease.

In a clinical trial,sometimes patients agree to receive an intervention but later decide to stop taking the medication.Moreover,some patients who were assigned to placebo decide to stop taking the placebo pill and buy the drug on their own (even when they do not know that they are taking a placebo pill) .When this happens,researchers typically do the analysis according to the original assignment of the treatment regardless of the actual treatment received.What is the name of this procedure to analyze the data?

A) Randomization
B) Intention-to-treat analysis
C) Concealment of random allocation
D) Analysis as treated
E) Mediation analysis

What is the attack rate (case-fatality rate) from influenza during the 2016 season in the young age group at Minas Tirith? Use the following table to answer the question. Number of Residents,Diagnosed Cases,and Deaths From Influenza by Age
$$\begin{array}{llll}\text{ Age group }& \begin{array}{l}\text{ No. of residents }\\ \text{ during }2016\text{ season }\end{array}& \begin{array}{l}\text{ No. of diagnosed }\\ \text{ cases from influenza }\\ \text{ during }2016\text{ season }\end{array}& \begin{array}{l}\text{ No. of deaths from }\\ \text{ influenza during }2016\\ \text{ season }\end{array}\\ \text{ Young }& 20,000& 3,000& 300\\ \text{ Old }& 10,000& 1,000& 500\end{array}$$


A) 15%
B) 5%
C) 1.5%
D) 10%
E) 50%

For a disease such as seasonal influenza,which is less fatal and of short duration?

A) Incidence rates and mortality rates will be similar.
B) Mortality rates will be much higher than incidence rates.
C) Incidence rates will be much higher than mortality rates.
D) Incidence rates will be unrelated to mortality rates.
E) None of the above.

During the conquest of Mexico,outbreaks played an important role that favored the Spaniards.There were several outbreaks of smallpox that killed thousands of natives.Smallpox was introduced into America by the Europeans.Why were the natives particularly afflicted by smallpox outbreaks?

A) Among natives, the proportion of susceptibles was higher.
B) Among Spaniards, the proportion of immunes was extremely low.
C) Spaniards had the cure for smallpox.
D) Natives had a gene that made them more prone to die from smallpox.
E) Spaniards were protected from smallpox because they had armors.

What is the best measure of association to explain what percentage of the new diagnoses of disease X are explained by exposure to Y among those exposed to Y?

A) Relative risk
B) Risk ratio
C) Odds ratio
D) Attributable risk
E) Incidence rate ratio

The following are problems generated when a patient is given a false-positive diagnosis,except:

A) Generate unnecessary expenses, as those labeled positive often go through other diagnostic procedures.
B) Generates anxiety and worry.
C) Increased burden to the healthcare system
D) The opportunity for an effective intervention is missed.
E) Unnecessary treatments are administered.

In a case-control study,a researcher found no association between exposure to A and disease B.Later she found out that there was a misclassification when measuring exposure to A,in both cases and controls.What is a potential explanation for the results (no association) of this case-control study?

A) Nondifferential misclassification
B) Differential misclassification
C) Selection bias
D) Confounding
E) Effect-modification

Which of the following statement about positive predictive value is the most accurate?

A) Positive predictive value is a fixed characteristic of the test. It will not change over the person, place, and time.
B) Positive predictive value is affected by the sensitivity of the test only.
C) Specificity will not affect the positive predictive value.
D) Positive predictive value is the probability that a diseased person (case) in the population tested will be identified as diseased by the test.
E) None of above.

Which term most accurately describes the following definition? "The observational epidemiological study of persons with the disease (or another outcome variable) of interest and a suitable control group of persons without the disease (comparison group,reference group) ." [Porta M,ed.A Dictionary of Epidemiology.New York: Oxford University Press; 2014.]

A) Ecologic study
B) Cross-sectional study
C) Case-control study
D) Cohort study
E) Randomized trial

An epidemiologist decides to investigate the incidence of diabetes in a population of 300 older adults who live in a nursing home.She visits the nursing home in January 1,2017 and later in December 31 of the same year.She looks into the records of these patients and learns that in her first visit,25 patients had diabetes and 35 in her second visit.What number should be in the numerator for her calculation of incidence?

A) 10
B) 25
C) 35
D) 300
E) 275

What is the name of the occurrence of a clearly higher than expected number of cases of a disease within a limited geographical region?

A) Pandemic
B) Epidemic
C) Endemic
D) Zoonosis
E) Attack rate

A physical examination,digital rectal exam,was used to screen for prostate cancer in 290 men with biopsy-proven prostate cancer and in 516 age- and race-matched control men,all of whom showed no evidence of cancer at biopsy.The results of the physical examination were positive in 136 cases and in 165 control men.Now,the health commissioner in City A decides to use a physical exam,digital rectal exam,as a primary screening test for prostate cancer.What will be the positive predictive value of the physical examination?

A) 45%
B) 47%
C) 68%
D) 82%
E) Cannot calculate it based on given information