Epidemiology Practice Questions

Q: Which of the following is a measure of incidence in epidemiology?

Incidence Rate. ***Incidence Rate*** - **Incidence rate** measures the speed at which new cases of a disease occur in a population at risk over a specified period. - It is calculated as the **number of new cases** divided by the total person-time at risk. *Prevalence* - **Prevalence** measures the proportion of individuals in a population who have a disease at a specific point in time or over a period. - It includes **both new and existing cases** and does not directly measure the rate of new disease occurrence. *Case Fatality Rate* - The **case fatality rate** (CFR) is the proportion of individuals diagnosed with a disease who die from that disease. - It is a measure of the **severity of a disease** and not a measure of how frequently new cases arise. *Mortality Rate* - The **mortality rate** measures the frequency of death in a defined population during a specified period. - While related to disease, it focuses on **deaths** rather than the occurrence of new disease cases.

Q: Which of the following is included in the Integrated Disease Surveillance Programme (IDSP)?

All are included. ***All are included*** - The **Integrated Disease Surveillance Programme (IDSP)**, launched in 2004, has significantly **evolved and expanded** its scope over the years. - Currently, IDSP covers **surveillance of communicable diseases** (epidemic-prone diseases like cholera, dengue, malaria, measles, tuberculosis, COVID-19). - The programme now also includes **surveillance of non-communicable diseases** such as diabetes, hypertension, cardiovascular diseases, and cancer as part of India's comprehensive health surveillance strategy. - **Environmental surveillance** is integrated into IDSP for monitoring climate-sensitive diseases, vector-borne disease patterns, water quality in outbreak contexts, and environmental factors influencing disease transmission. - IDSP operates through a **decentralized, state-based surveillance system** with laboratory networks and IT-enabled reporting mechanisms under the Integrated Health Information Platform (IHIP). *Surveillance of communicable diseases* - While this is correct and remains the **core focus** of IDSP since its inception, it is **not the only component**. - This option is incomplete as it excludes the expanded mandate of the programme. *Surveillance of non-communicable diseases* - This is now **included in IDSP** as the programme has evolved beyond its original communicable disease focus. - However, this alone does not represent the complete scope of IDSP. *Collection of environmental data* - Environmental surveillance **is part of IDSP** for monitoring factors affecting disease patterns, particularly for climate-sensitive and vector-borne diseases. - This includes monitoring environmental determinants of health and disease outbreaks.

Q: Which of the following is a characteristic of a cross-sectional study?

Measures prevalence of a disease.. ***Measures prevalence of a disease.*** - Cross-sectional studies collect data on both **exposure** and **outcome** at a single point in time, allowing for the calculation of disease **prevalence**. - They provide a **snapshot** of the health status and characteristics of a population at a specific moment. *Establishes a causal relationship.* - Cross-sectional studies often suffer from **reverse causality** or **temporality issues**, making it difficult to determine whether the exposure preceded the outcome. - Due to the simultaneous measurement of exposure and outcome, one cannot definitively conclude a **cause-and-effect relationship**. *Follows participants over time.* - This characteristic is typical of **longitudinal studies**, such as cohort studies, which track individuals over a period to observe changes or outcomes. - Cross-sectional studies are conducted at **one specific time point** and do not involve follow-up periods. *Used to measure incidence of a disease.* - **Incidence** refers to the rate of new cases of a disease in a population over a specified period, requiring follow-up over time. - This measure is typically obtained from **cohort studies** or clinical trials, not from a single-point-in-time cross-sectional study.

Q: In a case-control study investigating the link between smoking and lung cancer, which measure of association is the most appropriate?

Odds ratio. ***Odds ratio*** - The **odds ratio** is the most appropriate measure of association for **case-control studies** because these studies select participants based on disease status, making direct calculation of incidence or relative risk impossible. - It approximates the **relative risk** when the disease is rare, providing a valid estimate of the association between the exposure (smoking) and the outcome (lung cancer). *Relative risk* - **Relative risk** is calculated in **cohort studies** where participants are followed over time to observe the incidence of disease in exposed versus unexposed groups. - It cannot be directly calculated in a **case-control study** because the study design ascertains cases and controls based on outcome, not exposure status. *Attributable risk* - **Attributable risk**, also known as risk difference, measures the absolute excess risk of disease in the exposed group compared to the unexposed group. - Like relative risk, it is primarily used in **cohort studies** to determine the benefit of removing an exposure, and it requires incidence data. *Incidence rate* - **Incidence rate** measures the frequency with which new cases of disease occur in a population at risk over a specified period. - It is a measure reported in **cohort studies** or surveillance studies, not typically in case-control studies, which are designed to compare exposures between cases and controls.

Q: During a mass screening program for diabetes, a new test with a sensitivity of 85% and specificity of 90% is used. If the test is applied to a population with a low prevalence of diabetes, what is the most likely outcome?

Increased false positive results due to low prevalence. ***Increased false positive results due to low prevalence*** - In a population with **low disease prevalence**, even a test with high specificity will yield a significant number of **false positives** because there are many healthy individuals who will test positive. - While sensitivity and specificity are intrinsic to the test, the **positive predictive value (PPV)**, which reflects the likelihood of actually having the disease when testing positive, decreases dramatically with lower disease prevalence. *Increased true positive results due to high sensitivity* - While **high sensitivity** does mean that a large proportion of truly diseased individuals will be correctly identified as positive, the absolute number of **true positives** will be low if the disease itself is rare in the population. - The number of true positives is also directly limited by the **prevalence** of the disease. *Increased false negative results due to low prevalence* - **False negative results** are primarily influenced by the test's **sensitivity**, not directly by prevalence. A test with 85% sensitivity will miss 15% of true cases, regardless of how common or rare the disease is. - Low prevalence means there are fewer actual cases to begin with, so the absolute number of false negatives might be low, but the *proportion* of missed cases among true positives remains related to sensitivity. *Equal false positive and false negative results* - It is highly unlikely for **false positive** and **false negative** rates to be equal, as they are determined by different test characteristics (**specificity** and **sensitivity**, respectively) which are independent. - The impact of prevalence primarily skews the balance between false positives and true positives, and false negatives and true negatives.

Q: Why is scabies frequently associated with outbreaks in institutional settings?

Direct skin-to-skin contact is common. ***Direct skin-to-skin contact is common*** - **Scabies** is primarily transmitted through **prolonged direct skin-to-skin contact**, which is unavoidable in close-quarter institutional settings like nursing homes, hospitals, and daycare centers. - This close proximity facilitates the transfer of the **Sarcoptes scabiei mite** from an infected individual to others. *It spreads via airborne droplets* - Scabies mites are **not airborne** and do not spread through respiratory droplets like viruses (e.g., influenza, common cold). - Transmission requires physical contact, making airborne spread an incorrect mechanism. *The mites survive longer on surfaces* - While *Sarcoptes scabiei* mites can survive off a human host for a short period (typically 24-72 hours), their **survival on inanimate surfaces is limited** and generally not the primary mode of transmission. - Transmission mainly occurs through direct human-to-human contact. *It is transmitted through contaminated food* - Scabies is a **skin infestation** and is **not transmitted via ingestion of contaminated food**. - Foodborne illnesses are caused by pathogens in food, whereas scabies is a parasitic dermatological condition.

Question 1

Which of the following is a measure of incidence in epidemiology?

Accepted Answer

Incidence Rate

Answer

Prevalence

Answer

Case Fatality Rate

Answer

Mortality Rate

Question 2

A public health researcher is comparing the effectiveness of two vaccines using a cohort study. After calculating the relative risk, the researcher finds an RR of 0.5 for Vaccine A compared to Vaccine B. What does this result indicate about Vaccine A?

Accepted Answer

Vaccine A reduces the risk of disease by 50% compared to Vaccine B.

Answer

Vaccine A increases the risk of disease by 50% compared to Vaccine B.

Answer

Vaccine A has no effect on disease risk compared to Vaccine B.

Answer

Vaccine A and Vaccine B are equally effective.

Question 3

What is the aim of the Integrated Disease Surveillance Project (IDSP)?

Accepted Answer

A systematic approach to detect and respond to communicable and non-communicable diseases

Answer

An insurance scheme for chronic illnesses

Answer

A database for genetic diseases

Answer

A research platform for developing new drugs

Question 4

In a cohort study, the relative risk (RR) of developing lung cancer in smokers compared to non-smokers is 5. What does this indicate?

Accepted Answer

Smokers are five times more likely to develop lung cancer compared to non-smokers.

Answer

Lung cancer is five times more common in the general population.

Answer

There is a 5% chance of developing lung cancer in smokers.

Answer

A fixed proportion of smokers will develop lung cancer.

Question 5

Which of the following is included in the Integrated Disease Surveillance Programme (IDSP)?

Accepted Answer

All are included

Answer

Surveillance of communicable diseases

Answer

Surveillance of non-communicable diseases

Answer

Collection of environmental data

Question 6

Which of the following is a characteristic of a cross-sectional study?

Accepted Answer

Measures prevalence of a disease.

Answer

Establishes a causal relationship.

Answer

Follows participants over time.

Answer

Used to measure incidence of a disease.

Question 7

In a case-control study investigating the link between smoking and lung cancer, which measure of association is the most appropriate?

Accepted Answer

Odds ratio

Answer

Relative risk

Answer

Attributable risk

Answer

Incidence rate

Question 8

Which of the following factors should be critically evaluated before introducing a new vaccine for tuberculosis in a high-burden country?

Accepted Answer

Efficacy of the vaccine and availability of healthcare infrastructure.

Answer

Prevalence of tuberculosis and political stability in the region.

Answer

Cost-effectiveness and cultural acceptance of the vaccine.

Answer

None of the options.

Question 9

During a mass screening program for diabetes, a new test with a sensitivity of 85% and specificity of 90% is used. If the test is applied to a population with a low prevalence of diabetes, what is the most likely outcome?

Accepted Answer

Increased false positive results due to low prevalence

Answer

Increased true positive results due to high sensitivity

Answer

Increased false negative results due to low prevalence

Answer

Equal false positive and false negative results

Question 10

Why is scabies frequently associated with outbreaks in institutional settings?

Accepted Answer

Direct skin-to-skin contact is common

Answer

It spreads via airborne droplets

Answer

The mites survive longer on surfaces

Answer

It is transmitted through contaminated food

Epidemiology — MCQs

Epidemiology — MCQs

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