Epidemiology Practice Questions

Q: Sullivan’s index is an indicator of:

Disability. ***Disability*** - Sullivan's index, also known as **disability-free life expectancy**, is a measure that combines **mortality** and **morbidity** data to estimate the expected years an individual will live without disability. - It's a key indicator of the average number of years a person can expect to live in a **healthy or non-disabled state.** *Morbidity* - While related to morbidity, Sullivan's index specifically measures the **absence of disability**, rather than just the presence of disease or illness. - **Morbidity** refers to the state of being diseased or unhealthy, without necessarily quantifying the impact on daily function. *Mortality* - **Mortality** refers to the death rate or the number of deaths in a population. Sullivan's index uses mortality data in its calculation but is not solely an indicator of mortality. - It combines mortality with information on disability to provide a more nuanced picture of **population health.** *Health care delivery* - **Health care delivery** refers to the organization and provision of medical services. Sullivan's index measures health outcomes and does not directly indicate the quality or efficiency of healthcare delivery systems. - While improved healthcare can influence disability-free life expectancy, the index itself is a **health status measure**, not a healthcare system measure.

Q: ‘Spot map’ in epidemiological studies refer to variation in the distribution of a disease at:

Local level. ***Local level*** - A **spot map** is an epidemiological tool used to visualize the geographical distribution of disease cases within a **small, defined area**, such as a neighborhood or a single city. - It helps in identifying **clusters or hot-spots** of disease occurrence, which can be crucial for locating potential sources of infection or environmental hazards. *International level* - While disease distribution can be mapped internationally, a "spot map" specifically refers to a **finer-grain analysis** at a much smaller geographical scale, not across multiple countries. - Maps at the international level are often used for **global burden of disease** studies or pandemic tracking, which require broader summaries rather than individual case plotting. *Rural – urban level* - Mapping at the rural-urban level indicates differences between these two broad categories, but a spot map provides even more specific detail within those areas. - It shows the precise location of cases, allowing for insights into localized environmental or social factors, rather than just a general rural vs. urban comparison. *National level* - National-level mapping provides an overview of disease prevalence or incidence across an entire country, which is a much larger scale than a spot map. - A spot map is designed to highlight **precise locations** of cases within a more contained geographical area, making it less suitable for broad national-level trends.

Q: Severity of a disease is measured by:

Case fatality rate. ***Case fatality rate*** - The **case fatality rate (CFR)** directly measures the **severity** of a disease by indicating the proportion of individuals diagnosed with a disease who ultimately die from it. - A higher CFR implies a more lethal or severe disease. *Incidence rate* - The **incidence rate** measures the **frequency of new cases** of a disease in a population over a specified period. - It reflects how quickly a disease is spreading, not its severity. *Attributable risk* - **Attributable risk (AR)** quantifies the proportion of disease incidence in an exposed group that can be attributed to the exposure. - It measures the **public health impact** of an exposure, not the inherent severity of the disease itself. *Relative risk* - **Relative risk (RR)** compares the probability of an event (e.g., disease development) in an **exposed group** to the probability of the event in an **unexposed group**. - It indicates the **strength of association** between an exposure and a disease, not the severity of the disease in affected individuals.

Q: An outbreak of Viral Hepatitis was reported from a town between June and August of a particular year. 60% of cases occurred in July. Exposure of the community to infection is from:

A single source for a short period. ***A single source for a short period*** - This describes a **point source outbreak**, the classic pattern seen in this scenario - **60% of cases in July** indicates exposure occurred over a **brief period** (likely days to weeks before July) - The 3-month span (June-August) represents the **distribution of cases around the incubation period** of viral hepatitis (typically 2-6 weeks for Hepatitis A) - Common examples: **contaminated water supply**, food at a community gathering, or other single exposure event - This is the **textbook presentation** of a point source epidemic with a characteristic sharp peak *Multiple sources for a short period* - This would produce **multiple peaks** or an irregular epidemic curve, not a single peak in July - Multiple sources would not create the concentrated 60% clustering observed - The pattern described is too uniform for multiple independent sources *A common single source for prolonged periods* - This describes a **continuous common source outbreak** with an extended epidemic curve - Cases would be **distributed more evenly** across June-August without a sharp peak - Example: ongoing contamination of a water supply over months - The 60% concentration in July rules out this pattern *Multiple sources over prolonged periods* - This would result in **endemic disease** or a very flat, prolonged epidemic curve - No sharp peak would be observed - The temporal clustering contradicts this pattern

Q: Due to which of the following does seasonal trend of a disease occur? 1. Vector variation 2. Environmental factors 3. Change in herd immunity Select the correct answer using the code given below:

1, 2 and 3. ***1, 2 and 3*** - **Vector variation** (e.g., mosquito populations increasing during warmer months) is a critical factor causing seasonal patterns in vector-borne diseases like malaria, dengue, and Japanese encephalitis. - **Environmental factors** such as temperature, humidity, and rainfall directly affect pathogen survival, vector breeding, transmission efficiency, and host susceptibility, leading to characteristic seasonal patterns (e.g., respiratory infections in winter, diarrheal diseases in summer). - **Changes in herd immunity** can contribute to temporal disease patterns, though this factor more commonly drives long-term cyclical patterns (multi-year cycles) rather than short-term seasonal variations. The accumulation of susceptible individuals (through births) and waning immunity can influence disease occurrence patterns over time. *2 and 3 only* - This option incorrectly excludes **vector variation**, which is a primary determinant of seasonality for many infectious diseases, particularly arthropod-borne infections. - Vector activity shows marked seasonal fluctuations that directly correlate with disease incidence. *1 and 3 only* - This option incorrectly excludes **environmental factors**, which are fundamental drivers of seasonal disease patterns. - Temperature, humidity, precipitation, and other climatic variables directly influence pathogen viability, vector ecology, and human behavioral patterns that affect disease transmission. *1 only* - This option is too restrictive, considering only **vector variation** while neglecting the significant contributions of **environmental factors** and **temporal changes in population immunity** to disease occurrence patterns. - Seasonal trends result from complex interactions among multiple factors.

Q: The pattern of disease in a community described in terms of the important factors which influence its occurrence is known as:

Community diagnosis. ***Community diagnosis*** - This term refers to the process of identifying and characterizing the health problems and needs of a **defined population** or community, considering influencing factors. - It involves analyzing health status, risk factors, and available resources to plan effective interventions. *Experimental epidemiology* - This involves conducting **randomized controlled trials** and other intervention studies to test hypotheses about cause-and-effect relationships in disease. - It focuses on evaluating the effectiveness of interventions, rather than describing the entire pattern of disease occurrence. *Confounding* - **Confounding** occurs when a third variable distorts the observed association between an exposure and an outcome. - It is a bias that can mislead conclusions in observational studies, not a description of the disease pattern itself. *Iceberg phenomenon* - The **iceberg phenomenon** illustrates that only a fraction of severe cases of a disease (the "tip of the iceberg") are clinically apparent, while a larger proportion of subclinical or asymptomatic cases remain hidden. - It describes the hidden burden of disease, not the overall pattern or influencing factors.

Q: Which of the following statements is/are true about proportional case rate of malaria? 1. This indicator is used since morbidity rate is difficult to determine 2. This is defined as the number of cases of malaria for every 100 patients seen in hospital OPDs 3. It is a crude index since cases are not related to their time and space distribution Select the correct answer using the code given below:

1, 2 and 3. ***1, 2 and 3*** - All three statements accurately describe the **proportional case rate of malaria** (also known as proportional morbidity). - Statement 1 is correct: This indicator is used because calculating true **morbidity rates** requires accurate population denominator data, which is often difficult to obtain in resource-limited settings. The proportional case rate provides a practical alternative using hospital-based data. - Statement 2 is correct: It is defined as **(Number of malaria cases / Total OPD patients) × 100**, representing malaria cases per 100 patients seen in hospital outpatient departments. - Statement 3 is correct: It is a **crude index** because it's a ratio (not a true rate) that doesn't account for the population at risk, temporal trends, or geographical distribution of cases. It merely reflects the relative burden among those seeking care. *2 only* - This option is incomplete. While statement 2 correctly defines the calculation method, it incorrectly excludes statements 1 and 3, which are also true. - The proportional case rate is indeed calculated as malaria cases per 100 OPD patients, but this alone doesn't explain its purpose or limitations. *3 only* - This option is incomplete. While statement 3 correctly identifies it as a **crude index** with limitations in temporal and spatial analysis, it incorrectly excludes statements 1 and 2. - Understanding why it's crude (statement 3) without knowing why it's used (statement 1) and how it's calculated (statement 2) provides an incomplete picture. *2 and 3 only* - This option is incomplete. While statements 2 and 3 are both correct, it incorrectly excludes statement 1. - The fundamental rationale for using proportional case rate—the difficulty in determining true morbidity rates—is missing, making this option less comprehensive than the correct answer.

Question 1

Which one of the following statements is correct regarding diabetes epidemiology?

Accepted Answer

Maternal diabetes increases the risk of subsequent diabetes.

Answer

Females are 2.5 times more at risk.

Answer

Its prevalence is not affected by age.

Answer

Central obesity is not linked with diabetes.

Question 2

Sullivan’s index is an indicator of:

Accepted Answer

Disability

Answer

Morbidity

Answer

Mortality

Answer

Health care delivery

Question 3

With reference to historical cohort study, which of the following statements is not correct?

Accepted Answer

Control subjects are selected from the current population without exposure.

Answer

Duration of study is shorter as compared to current cohort study.

Answer

Experience of cohort is assessed from existing records.

Answer

Outcomes have occurred before the start of the investigation.

Question 4

Specificity of a test is =

Accepted Answer

(True negatives X 100) / (True negatives + False positives) %

Answer

(True positives X 100) / (True negatives + False positives) %

Answer

(True positives X 100) / (True positives + False negatives) %

Answer

(True negatives X 100) / (True positives + True negatives) %

Question 5

‘Spot map’ in epidemiological studies refer to variation in the distribution of a disease at:

Accepted Answer

Local level

Answer

International level

Answer

Rural – urban level

Answer

National level

Question 6

Severity of a disease is measured by:

Accepted Answer

Case fatality rate

Answer

Incidence rate

Answer

Attributable risk

Answer

Relative risk

Question 7

An outbreak of Viral Hepatitis was reported from a town between June and August of a particular year. 60% of cases occurred in July. Exposure of the community to infection is from:

Accepted Answer

A single source for a short period

Answer

Multiple sources over prolonged periods

Answer

Multiple sources for a short period

Answer

A common single source for prolonged periods

Question 8

Due to which of the following does seasonal trend of a disease occur?

1. Vector variation
2. Environmental factors
3. Change in herd immunity

Select the correct answer using the code given below:

Accepted Answer

1, 2 and 3

Answer

2 and 3 only

Answer

1 and 3 only

Answer

1 only

Question 9

The pattern of disease in a community described in terms of the important factors which influence its occurrence is known as:

Accepted Answer

Community diagnosis

Answer

Experimental epidemiology

Answer

Confounding

Answer

Iceberg phenomenon

Question 10

Which of the following statements is/are true about proportional case rate of malaria?

1. This indicator is used since morbidity rate is difficult to determine
2. This is defined as the number of cases of malaria for every 100 patients seen in hospital OPDs
3. It is a crude index since cases are not related to their time and space distribution

Select the correct answer using the code given below:

Accepted Answer

1, 2 and 3

Answer

2 only

Answer

3 only

Answer

2 and 3 only

Epidemiology — MCQs

Epidemiology — MCQs

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