Brown Invitational — Disease Detectives

Disease Detectives · Division B · Brown Invitational · 2026

81 questions · 129 points · 50 min· 8 questions from the original omitted

Instructions and Advice: • DO NOT WRITE ON THE EXAM • Allowed materials: one 8.5x11 double-sided reference sheet and two (2) stand-alone, non-programmable, non-graphing calculators. • You do not have to show your work unless you are explicitly asked to do so. Partial credit may be awarded if correct work is shown in these cases. • Round all calculations to the tenths place, if necessary. • Good luck!

Part 1: General Knowledge

Word bankFor questions 1-1–1-20

a.Selection Bias
b.Information Bias
c.Collider Bias
d.Effect Modification
e.Attributable Risk
f.Population Attributable Fraction
g.Odds Ratio
h.Relative Risk
i.Ecological Fallacy
j.Healthy Worker Effect
k.Misclassification
l.Surveillance Bias
m.Recall Bias
n.Temporal Relationship
o.Dose-Response Relationship
p.Standardization
q.Interaction
r.Point Source Outbreak
s.Continuous Common Source Outbreak
t.Propagated Outbreak

Question 1-1

1 pt

Match the term with the description: A bias introduced when an analysis conditions on, or selects participants based on, a variable that is influenced by both the exposure and the outcome.

Question 1-2

1 pt

Match the term with the description: A method used to remove the effects of differences in age or other factors when comparing two or more populations.

Question 1-3

1 pt

Match the term with the description: A pattern in which increasing levels of exposure correspond to increasing (or decreasing) levels of risk, supporting causality.

Question 1-4

1 pt

Match the term with the description: An outbreak resulting from ongoing exposure to a contaminated source over an extended period.

Question 1-5

1 pt

Match the term with the description: The difference in disease risk between exposed and unexposed groups that can be attributed to the exposure itself.

Question 1-6

1 pt

Match the term with the description: Bias resulting from differences in the accuracy or completeness of recalled information between study groups.

Question 1-7

1 pt

Match the term with the description: An error that arises when associations observed at the group level do not necessarily hold true for individuals within those groups.

Question 1-8

1 pt

Match the term with the description: A measure of association commonly used in case-control studies, representing the odds of exposure among cases compared to controls.

Question 1-9

1 pt

Match the term with the description: Bias introduced when increased medical observation or testing in one group leads to higher reported disease incidence.

Question 1-10

1 pt

Match the term with the description: A systematic error that occurs when study participants differ from the target population in ways related to both exposure and outcome.

Question 1-11

1 pt

Match the term with the description: When two variables act together to produce a combined effect greater (or different) than the sum of their individual effects.

Question 1-12

1 pt

Match the term with the description: The proportion of all cases in the population that can be attributed to a specific exposure.

Question 1-13

1 pt

Match the term with the description: A type of information bias that occurs when individuals are incorrectly categorized regarding exposure or disease status.

Question 1-14

1 pt

Match the term with the description: A principle stating that exposure must precede the onset of disease to establish causation.

Question 1-15

1 pt

Match the term with the description: A measure of association used in cohort studies, comparing the risk of disease in exposed versus unexposed groups.

Question 1-16

1 pt

Match the term with the description: A situation in which the effect of an exposure on an outcome varies across levels of another variable.

Question 1-17

1 pt

Match the term with the description: An outbreak that spreads person-to-person through direct or indirect contact, producing multiple waves of infection.

Question 1-18

1 pt

Match the term with the description: A type of selection bias in which employed populations tend to appear healthier than the general population.

Question 1-19

1 pt

Match the term with the description: A distortion in study results arising from inaccurate measurement or reporting of exposure or outcome data.

Question 1-20

1 pt

Match the term with the description: An outbreak that originates from a single, brief exposure source, typically producing a sharp rise and fall in cases.

Multiple Choice

Question M1

1 pt

The index case is:

A. The first case that occurredB. The first case detected by investigatorsC. The case with the most severe symptomsD. The last case in an outbreak

Question M2

1 pt

Which is an example of vector-borne transmission?

A. SneezingB. Contaminated foodC. Mosquito biteD. Touching a doorknob

Question M3

1 pt

Screening blood donations for HIV is what level of prevention?

A. PrimaryB. SecondaryC. TertiaryD. Quaternary

Question M4

1 pt

The first step when an apparent cluster of illness is reported is to:

A. Establish a case definitionB. Verify the diagnosis and confirm an outbreak existsC. Perform laboratory testingD. Interview exposed persons

Question M5

1 pt

A disease that persists at a constant level within a population is:

A. SporadicB. EndemicC. EpidemicD. Pandemic

Question M6

1 pt

Investigators identify children with asthma and compare their past exposures to those without asthma. This study is:

A. Case-controlB. Prospective cohortC. Cross-sectionalD. Experimental

Question M7

1 pt

Participants who know they are receiving a new vaccine may report fewer symptoms due to expectations. This is:

A. Recall biasB. Observer biasC. Information biasD. Placebo effect

Question M8

1 pt

A broad case definition will:

A. Increase sensitivity but lower specificityB. Increase specificity but lower sensitivityC. Reduce bothD. Improve accuracy

Question M9

1 pt

An odds ratio of 1.0 means:

A. Strong associationB. Weak associationC. No associationD. Protective association

Question M10

1 pt

The portal of exit for Mycobacterium tuberculosis:

A. Respiratory tractB. FecesC. Skin lesionD. Blood

Question M11

1 pt

An epidemic curve shows a sharp single peak within 24 hours after a picnic. The exposure is most likely:

A. Continuous common sourceB. PropagatedC. Point sourceD. Endemic

Question M12

1 pt

If illness peaks 3 days after a wedding dinner, the mean incubation period for the pathogen is:

A. 1 dayB. 3 daysC. 5 daysD. 7 days

Part 2: Meningtitis Outbreak

PassageFor questions 2-1–2-2

On November 5th, 2025, Brown University Health was notified that two first-year students were hospitalized with fever, severe headache, stiff neck, and rashes. Over the next week, three more students developed similar symptoms. Two of these students were roommates of the first hospitalized patients. All five students tested positive for Neisseria meningitidis serogroup B, a bacterium that can cause meningococcal meningitis.

Question 2-1

4 pts

Write an appropriate case definition for this outbreak. Include person, place, time, and clinical criteria.

Question 2-2

1 pt

What is the most likely mode of transmission for this disease?

PassageFor questions 2-3–2-4

Upon further investigation, Brown University Health found that all five students lived in the same dorm and had all attended their dorm’s Halloween party the previous weekend. Brown University Health conducted a study among 300 students at Brown living in the same dorm as those infected. The researchers asked the students about their attendance at the Halloween party and whether or not they became sick.

Question 2-3

1 pt

What kind of study is described above?

Question 2-4

2 pts

Explain one advantage and one disadvantage of this type of study.

FigureFor questions 2-5, 2-6a, 2-6b, 2-6c, 2-7–2-8, 2-9a, 2-9b, 2-9c, 2-9d, 2-10a, 2-10b

Question 2-5

13 pts

Fill out the table below.

Question 2-6a

2 pts

Calculate the attack rate among students who attended the party (show all work).

Question 2-6b

2 pts

Calculate the attack rate among students who did not attend the party (show all work).

Question 2-6c

2 pts

Calculate the relative risk (show all work).

Question 2-7

2 pts

Interpret the relative risk. What does this tell you about the risk associated with attending the party?

Question 2-8

2 pts

If this is a propagated outbreak, what would you expect the epidemic curve to look like?

Question 2-9a

1 pt

The university offers meningococcal B vaccination to all first-year students and antibiotic prophylaxis to close contacts of cases. Which step of the chain of infection does vaccination target?

Question 2-9b

1 pt

The university offers meningococcal B vaccination to all first-year students and antibiotic prophylaxis to close contacts of cases.

Which step of the chain of infection does antibiotic prophylaxis target?

Question 2-9c

1 pt

The university offers meningococcal B vaccination to all first-year students and antibiotic prophylaxis to close contacts of cases.

What level of prevention does vaccination represent?

Question 2-9d

1 pt

The university offers meningococcal B vaccination to all first-year students and antibiotic prophylaxis to close contacts of cases.

What level of prevention does antibiotic prophylaxis represent?

Question 2-10a

2 pts

A new case occurs three weeks later in a student who was fully vaccinated. Give two possible explanations for this case.

Question 2-10b

1 pt

How should investigators determine whether this case is part of the same outbreak?

Part 3: Alzheimer’s Disease

Question 3-1

0.5 pts

You carry one or more copies of the APOE-ε4 allele, which increases susceptibility to AD.

Question 3-2

0.5 pts

You begin to experience subtle memory lapses and mild confusion noticeable to friends or family.

Question 3-3

0.5 pts

Abnormal β-amyloid plaques and tau tangles begin accumulating silently in your brain.

Question 3-4

0.5 pts

You adopt a sedentary lifestyle with poor sleep and limited cognitive stimulation.

Question 3-5

0.5 pts

A neurologist formally diagnoses mild cognitive impairment (MCI) due to AD after neuropsychological testing.

Question 3-6

0.5 pts

You develop advanced dementia, requiring assistance with daily activities.

Question 3-7

0.5 pts

You die from complications of late-stage Alzheimer’s disease.

Question 3-8

0.5 pts

You are asymptomatic but show early biomarker positivity on PET imaging or CSF analysis.

Question 3-2b

2 pts

How can SNP mapping help identify genetic variations linked to Alzheimer’s risk in different populations?

Question 3-3b

1 pt

Can Koch’s Postulates be used to establish a link between amyloid accumulation and Alzheimer’s Disease? Explain.

Part 3: Alzheimer's Disease (continued)

Question 3-4

5 pts

Identify the level of prevention that each of the following measures represents.

Providing palliative and hospice care for patients in late-stage dementia.
Implementing cognitive training and physical-activity programs for middle-aged adults.
Establishing air-quality regulations and lead exposure limits to reduce neurotoxic risks.
Prescribing anti-amyloid monoclonal antibodies (e.g., lecanemab) to slow disease progression.
Using blood-based biomarker panels or PET imaging for early detection in at-risk individuals.

PassageFor questions 3-5–3-6

Researchers are developing NeuroVax, an experimental vaccine that stimulates antibody production against β-amyloid aggregates to prevent onset of AD in high-risk adults.

Question 3-5

1 pt

What type of immunity does this vaccine aim to produce? Be as specific as possible.

Question 3-6

1 pt

Is the concept of herd immunity relevant in this situation? Explain.

Suppose that the researchers have just completed a clinical trial testing the efficacy of this vaccine and have asked you to analyze the data shown below.

	Has Alzheimer's	No Alzheimer's
Received Vaccine	8	192
No Vaccine	80	120

Question 3-7

3 pts

Using the experimental data given above, calculate the efficacy of this vaccine as a percentage. Please show your work and provide an interpretation of your result.

Question 3-8

1 pt

Would a clinical trial like this be practical in real life? Why or why not?

As part of your analysis, you discover the following data on average nightly sleep duration and Alzheimer's disease.

	Has Alzheimer's	No Alzheimer's
< 6 Hours of Sleep	75	425
≥ 6 Hours of Sleep	50	950

Question 3-9

3 pts

Calculate the relative risk of developing AD for those sleeping less than 6 hours. Show your work and interpret your result.

Question 3-11

1 pt

In this study, sleep is a ____ variable.

A biotechnology company has developed a plasma phosphorylated-tau (p-tau217) assay for early diagnosis of Alzheimer's. The following data are collected from a validation study:

	Has Alzheimer's	No Alzheimer's
Positive Test Result	85	30
Negative Test Result	15	270

Question 3-12

1 pt

Briefly explain why early diagnosis is important for Alzheimer's.

Question 3-13a

1 pt

Using the data, calculate and interpret: Sensitivity

Question 3-13b

1 pt

Using the data, calculate and interpret: Specificity

Question 3-13c

1 pt

Using the data, calculate and interpret: Positive Predictive Value

Question 3-13d

1 pt

Using the data, calculate and interpret: Negative Predictive Value

Question 3-14

1 pt

Which test statistic corresponds to a Type I Error? Which one corresponds to a Type II error?

Question 3-15

2 pts

Which of these statistics is most important in the context of Alzheimer's screenings? Based on this answer, do you think that the company has developed a useful test? Explain.

Part 4: Menopause and Physical Function

PassageFor questions 4-1–4-3

In 2023, researchers conducted a study examining the physical function of women at different menopausal stages. 210 women were recruited for the study, categorized into pre-menopausal, peri-menopausal, and post-menopausal groups based on menopausal status at the time. Each participant was assessed once for flexibility, muscle strength and endurance, cardiovascular endurance, static and dynamic balance, and gait speed.

Question 4-1

2 pts

Name the study design used and give at least one advantage and disadvantage of this design.

Question 4-2

2 pts

Would you use relative risk or odds ratio as a primary measure of association for this study?

Question 4-3

3 pts

Under what condition is relative risk approximated by odds ratio? Hint: look at the formulas for both measures.

PassageFor questions 4-4–4-5

At the beginning of the results section in epidemiology papers, we tend to find a table listing demographic data for the groups that are being compared. This is colloquially known as Table 1. In this paper, we see that Table 1 includes characteristics such as age, weight, income level, physical activity level, chronic medical conditions.

Question 4-4

2 pts

What is the importance of this table for validating conclusions we make later on in 1-2 sentences?

Question 4-5

4 pts

This paper categorizes physical activity level as follows: often, not often, and not known. Briefly give 2 reasons you might be unsatisfied with this classification?

PassageFor questions 4-8–4-11

After conducting the physical assessments, the researchers compared the muscle strength of the 75 pre-menopausal and 80 post-menopausal women. 36% of pre-menopausal women were found to have "low" muscle strength, while 45% of post-menopausal women were found to have "normal" muscle strength.

Question 4-8

4 pts

Do you think the results indicate an association between menopausal stage and physical function? Explain your reasoning in 1-2 sentences.

Question 4-9

2 pts

Name the type of bias that occurs when subjects are selected for the sample because they are most accessible to the researchers.

Question 4-10

5 pts

Is the type of bias from the previous problem a concern to the researchers and why or why not? What specific part of their conclusion does it limit? Explain in 1-2 sentences.

Question 4-11

5 pts

Based on your answer to question 8 and the Bradford-Hill criterion, could this study be used to establish causal association between menopause and physical function? Explain your answer in 2-4 sentences.