Epidemiology Practice Questions

Q: Consider the following definition : "A high level of infection beginning early in life and affecting most of the child population, leading to a state of equilibrium such that the adult population shows evidence of the disease much less commonly than the children." Which one of the following terms best fits this definition?

Holoendemic. ***Holoendemic*** - This term describes a situation where an infection is **highly prevalent** early in life, affecting most children, leading to a state of **equilibrium** in adulthood where the disease is less common. - This pattern is often observed with diseases like **malaria** in endemic regions, where early exposure leads to acquired immunity. *Hyperendemic* - Refers to a disease that is **persistently present** at a **high level** of incidence and/or prevalence in a specific population, affecting all age groups, not specifically children. - While reflecting high prevalence, it doesn't emphasize the early-life infection leading to adult equilibrium as strongly as holoendemic. *Hypoendemic* - This term describes a disease with a **low level of incidence and prevalence** within a population. - It implies infrequent disease occurrence, which is the opposite of the high initial infection rate described in the definition. *Pandemic* - A **widespread epidemic** of an infectious disease that has spread across a large region, multiple continents, or even worldwide. - This term describes the geographical extent of a disease outbreak, not its specific pattern of age-related prevalence or immunity within a single population.

Q: A town in the hills had a mid-year population of 250000 in the year 2021. During the same year, the death registry of the town recorded 1500 deaths due to tuberculosis in 365 calendar days. Given these facts, what is the specific death rate for tuberculosis in the town?

6. ***6*** - The **specific death rate** (also called cause-specific death rate) is calculated as **(Number of deaths from a specific cause / Mid-year population) × 1000** - For tuberculosis: (1500 deaths / 250,000 population) × 1000 = **6 deaths per 1000 population** - This represents the tuberculosis mortality rate in the community *10* - This incorrect value would be obtained if there were 2500 deaths due to tuberculosis instead of 1500 - Calculation error: (2500 / 250,000) × 1000 = 10 - Always verify the numerator (number of deaths) from the given data *60* - This is a common calculation error resulting from incorrect multiplication factor - May occur if using: (1500 / 250,000) × 10,000 = 60 (wrong multiplier) - Remember: specific death rate uses **per 1000** population, not per 10,000 *1* - This value results from calculation errors or incorrect rounding - May occur if dividing by wrong population figure or forgetting the multiplier - The actual rate (1500/250,000 = 0.006) must be multiplied by 1000 to get rate per 1000 population

Q: In a town, a study was carried out to determine the role of cigarette smoking in causation of lung cancer. It was found that a total of 7000 people in the town were smokers. Of them, 70 developed lung cancer. In the same town, 3000 people were non-smokers. Of them, 3 developed lung cancer. Given these numbers, what would be the attributable risk to cigarette smoking for lung cancer?

90%. **90%** - The **attributable risk** (AR) is calculated as the incidence in the exposed group minus the incidence in the unexposed group, divided by the incidence in the exposed group, all multiplied by 100%. - Incidence in smokers (Ie) = 70 cases / 7000 smokers = 0.01. Incidence in nonsmokers (Io) = 3 cases / 3000 nonsmokers = 0.001. AR = ((0.01 - 0.001) / 0.01) * 100% = (0.009 / 0.01) * 100% = 0.9 * 100% = **90%**. *30%* - This percentage is incorrect; it does not align with the formal calculation of **attributable risk** based on the given incidence rates in exposed and unexposed groups. - A value of 30% would imply a much smaller difference in incidence between smokers and non-smokers relative to the incidence in smokers. *10%* - This value might be obtained if the calculation confused **attributable risk** with the proportion of cases in the unexposed group or some other miscalculation. - It significantly underestimates the proportion of lung cancer in smokers directly attributable to their smoking status. *60%* - This answer is incorrect as it does not result from the appropriate application of the **attributable risk formula**. - The discrepancy between the incidence rate in smokers (0.01) and non-smokers (0.001) is much higher than what would lead to a 60% attributable risk.

Q: Which of the following are correct in respect of incidence rate? 1. It is a sum total of new and old cases. 2. It refers to a specified period of time. 3. It refers to a defined population. 4. It must include the unit of time in final expression.

2. It refers to a specified period of time.. ***Statement 2: It refers to a specified period of time*** (Most Distinctive) - Incidence rate MUST be measured over a defined time interval (e.g., 1 year, 6 months) - This temporal component is the **key distinguishing feature** from point prevalence - Essential for calculating the rate at which new cases develop **Note:** Statements 3 and 4 are also technically correct about incidence rate: **Statement 3: It refers to a defined population** - Also correct - Incidence rate requires a clearly defined **population at risk** as denominator - However, this alone is not unique to incidence (prevalence also uses defined populations) **Statement 4: It must include the unit of time in final expression** - Also correct - Incidence **rate** is expressed per unit time: "cases per 1,000 person-years" - This distinguishes it from cumulative incidence (a proportion) - The time component IS part of the rate expression *Statement 1: It is a sum total of new and old cases* ✗ - This describes **prevalence**, not incidence - Incidence counts only **NEW cases** during the observation period - Existing (old) cases are excluded **Clarification:** While statement 2 is traditionally considered the most distinctive feature, epidemiologically statements 3 and 4 are also accurate characteristics of incidence rate. If the question asks "which are correct" (plural), technically 2, 3, and 4 would all be correct.

Q: Secular trends of diseases refer to

Changes in occurrence over long period of time. **Changes in occurrence over long period of time** - **Secular trends** describe the changes in the **frequency or pattern of a disease** or health condition over a long-term period, often spanning decades. - This concept is crucial in epidemiology for understanding the **evolution of diseases** and the impact of long-term public health interventions or societal changes. *Changes in incidence as per climate* - This refers to **seasonal variation** or **geographic variation** related to climate, not the sustained, long-term changes that define secular trends. - While climate can influence disease incidence, it typically causes cyclical or regional patterns rather than continuous long-term shifts. *Differences in incidence across different religions* - This describes **religious or cultural variations** in disease occurrence, which are a form of **social or demographic determinant**, but not secular trends. - Secular trends focus on changes over time, while religious differences are usually cross-sectional comparisons at a given point or period. *Variation in occurrence across various social strata* - This refers to **socioeconomic disparities** or **social gradients** in health outcomes, indicating differences between various social classes or groups. - While social factors can drive secular trends, secular trends specifically denote **changes over time**, not static differences between groups.

Q: In which system, continuous enumeration of births and deaths by enumerator and an independent survey by investigator supervisor is done?

Sample Registration System. ***Sample Registration System*** - This system employs a **dual record approach** where a local enumerator continuously records vital events (births and deaths), and an independent investigator supervisor conducts periodic surveys. - The combination of continuous enumeration and independent surveys helps to improve the **accuracy and completeness** of vital statistics by cross-checking data. *Decadal census enumeration* - This involves a **complete enumeration** of the population, typically conducted every ten years, to gather demographic and social data. - While it collects population counts and some vital statistics, it is not designed for **continuous monitoring** or a dual-record system for births and deaths. *Model Registration System* - This system focuses on developing and testing **improved methods** for vital event registration in a localized or pilot area. - It is not a nationwide system for continuous enumeration and independent surveys, but rather a framework for **methodological development**. *National Family Health Survey* - This is a large-scale, multi-round survey that provides data on **family health, fertility, child mortality**, and other health indicators. - It uses **recall methods** and questionnaires to collect data from households and does not involve continuous enumeration of births and deaths by enumerators or independent supervisor verification.

Q: The degree to which a specific health care intervention achieves its objectives, when applied in a given population, is termed as its

Effectiveness. ***Effectiveness*** - **Effectiveness** measures how well an intervention performs in a **real-world setting** under usual conditions in a given population [1] - It assesses the degree to which a healthcare intervention achieves its **intended objectives** when applied in actual practice (as opposed to controlled trial conditions) [1] - Key distinction: effectiveness = real-world performance; efficacy = performance under ideal/controlled conditions [1] *Sensitivity* - **Sensitivity** is a diagnostic test parameter measuring the proportion of actual positive cases correctly identified by the test - It relates to **test accuracy**, not to the achievement of intervention objectives in a population *Impact* - **Impact** refers to the broader, longer-term consequences of an intervention on **health outcomes** or population health status - While related to effectiveness, impact is a more **comprehensive measure** that includes indirect effects and long-term changes, not just the direct achievement of specific intervention objectives [1] *Efficiency* - **Efficiency** relates to the relationship between **resources used** (cost, time, personnel) and **results achieved** - It addresses whether an intervention achieves its objectives with **optimal resource utilization**, focusing on cost-effectiveness rather than simply whether objectives are met

Question 1

Consider the following definition : "A high level of infection beginning early in life and affecting most of the child population, leading to a state of equilibrium such that the adult population shows evidence of the disease much less commonly than the children." Which one of the following terms best fits this definition?

Accepted Answer

Holoendemic

Answer

Hyperendemic

Answer

Hypoendemic

Answer

Pandemic

Question 2

Which of the following statements are correct for incidence rate?

1. It is useful for taking action to control a disease.
2. Rising incidence rates may indicate ineffectiveness of the current control programmes.
3. Fluctuation in incidence rate may indicate a change in aetiology of disease. Select the answer using the code given below.

Accepted Answer

1, 2 and 3

Answer

2 and 3 only

Answer

1 and 3 only

Answer

1 and 2 only

Question 3

A town in the hills had a mid-year population of 250000 in the year 2021. During the same year, the death registry of the town recorded 1500 deaths due to tuberculosis in 365 calendar days. Given these facts, what is the specific death rate for tuberculosis in the town?

Accepted Answer

6

Answer

10

Answer

60

Answer

1

Question 4

In a town, a study was carried out to determine the role of cigarette smoking in causation of lung cancer. It was found that a total of 7000 people in the town were smokers. Of them, 70 developed lung cancer. In the same town, 3000 people were non-smokers. Of them, 3 developed lung cancer. Given these numbers, what would be the attributable risk to cigarette smoking for lung cancer?

Accepted Answer

90%

Answer

30%

Answer

10%

Answer

60%

Question 5

Which of the following are correct in respect of incidence rate?

1. It is a sum total of new and old cases.
2. It refers to a specified period of time.
3. It refers to a defined population.
4. It must include the unit of time in final expression.

Accepted Answer

2. It refers to a specified period of time.

Answer

1. It is a sum total of new and old cases.

Answer

4. It must include the unit of time in final expression.

Answer

3. It refers to a defined population.

Question 6

Which of the following is the most fundamental criterion that must be met by a disease before it is to be considered suitable for a screening programme?

1. The natural history of the disease should be adequately understood.
2. No effective treatment should exist for the disease.
3. The disease should not have a recognizable latent or asymptomatic stage.
4. There should be a test that can detect the disease prior to onset of signs and symptoms.

Accepted Answer

1. The natural history of the disease should be adequately understood.

Answer

4. There should be a test that can detect the disease prior to onset of signs and symptoms.

Answer

3. The disease should not have a recognizable latent or asymptomatic stage.

Answer

2. No effective treatment should exist for the disease.

Question 7

Virulence of a biological agent is defined as

Accepted Answer

Proportion of clinical cases resulting in severe clinical manifestation

Answer

Proportion of clinical cases in a virgin population

Answer

Ability of the agent to induce a clinically apparent illness

Answer

Ability of the agent to invade and multiply in a host

Question 8

Secular trends of diseases refer to

Accepted Answer

Changes in occurrence over long period of time

Answer

Changes in incidence as per climate

Answer

Differences in incidence across different religions

Answer

Variation in occurrence across various social strata

Question 9

In which system, continuous enumeration of births and deaths by enumerator and an independent survey by investigator supervisor is done?

Accepted Answer

Sample Registration System

Answer

Decadal census enumeration

Answer

Model Registration System

Answer

National Family Health Survey

Question 10

The degree to which a specific health care intervention achieves its objectives, when applied in a given population, is termed as its

Accepted Answer

Effectiveness

Answer

Sensitivity

Answer

Impact

Answer

Efficiency

Epidemiology — MCQs

Epidemiology — MCQs

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