Epidemiology Practice Questions

Q: The time period from entry of an infective agent into a host until the host develops the capacity for maximal infectivity is called:

Generation time. ***Generation time*** - This is defined as the time interval between **entry of an infective agent into a host** until the host develops **maximal infectivity**. - It represents the period from infection to when an infected individual is most capable of transmitting the disease to others. - This term precisely matches the question's definition and is crucial for understanding disease transmission dynamics. *Incubation period* - The incubation period is the time from exposure to an infectious agent until the onset of **clinical symptoms** in the host. - It ends at symptom onset, not at maximal infectivity (which may occur before, during, or after symptom onset depending on the disease). - While infectivity may peak during or near the incubation period for some diseases, this term specifically refers to symptom development, not infectivity capacity. *Serial interval* - The serial interval is the time between the onset of symptoms in a **primary case** and the onset of symptoms in a **secondary case**. - This describes the time between successive cases in a transmission chain, not the development of infectivity in an individual host. *Period of communicability* - This is the **entire duration** during which an infected person can transmit the infectious agent to others. - It describes the total infectious period (from start to end of infectivity), not specifically the time until **maximal** infectivity is reached.

Q: In a family of six (2 parents and 4 children), the youngest child catches measles infection. The parents are immune to the infection. On 3rd and 5th day of the infection of the first child, the two other children also suffer from measles. The secondary attack rate (SAR) of measles is:

66.6 %. ***66.6 %*** - The **secondary attack rate (SAR)** is calculated by dividing the number of new cases among susceptible contacts by the total number of susceptible contacts. - In this scenario, there are 3 susceptible children (the index case came from the 4 children, leaving 3 susceptible), and 2 of them developed measles, making the SAR (2/3) * 100 = **66.6%**. *40 %* - This percentage would be obtained if you incorrectly included the immune parents in the susceptible population or used the total family size in the denominator for susceptible individuals. - **Parents are immune**, hence they are not at risk, and should not be included in the denominator for calculating SAR among susceptible contacts. *50 %* - This would be the SAR if either 1 out of 2 susceptible contacts became ill, or 2 out of 4 susceptible contacts became ill. - In this case, 2 out of 3 susceptible children developed measles, not 2 out of 4, therefore this option is incorrect. *33.3 %* - This percentage would result if only 1 out of the 3 susceptible children developed measles, or 2 out of 6 total family members (including parents) who were susceptible fell ill. - Since **2 out of 3 susceptible children** became infected, this option is incorrect.

Q: Which one of the following statements is NOT true for taking a decision on screening for disease?

Proportion of false negatives is high. ***Proportion of false negatives is high*** - A **high proportion of false negatives** means that many individuals with the disease are missed by the screening test. - This is **absolutely undesirable** for screening and directly contradicts the fundamental principle that screening tests should have **high sensitivity**. - This statement is clearly NOT true as a criterion for making screening decisions. *Sensitivity and specificity are high* - **High sensitivity** means the test correctly identifies most people who have the disease, minimizing false negatives. - **High specificity** means the test correctly identifies most people who do not have the disease, minimizing false positives. - Both are desirable characteristics according to Wilson-Jungner screening criteria. *Disease prevalence should be high* - This statement is **oversimplified and not strictly accurate** according to Wilson-Jungner criteria. - The actual criterion is: **"The condition should be an important health problem"** - based on disease burden, severity, and consequences, NOT necessarily high prevalence. - Many successful screening programs target **low prevalence diseases** (e.g., phenylketonuria in newborns, congenital hypothyroidism). - What matters is the **positive predictive value (PPV)** and cost-effectiveness, which are influenced by prevalence but don't require "high" prevalence. *Disease is lethal* - The Wilson-Jungner criterion states the disease should have **"serious consequences if left untreated"** - this includes but is not limited to lethality. - Screening is justified for diseases causing **significant morbidity or mortality** where early detection improves outcomes. - The disease should be sufficiently serious to warrant the costs and potential harms of screening.

Q: The sequence of events leading to disability and handicap is:

Disease → Impairment→Disability→Handicap. ***Disease → Impairment→Disability→Handicap*** - This sequence follows the **WHO International Classification of Impairments, Disabilities, and Handicaps (ICIDH, 1980)** model, which correctly illustrates the progression from a health condition to its societal consequences. - A **disease** or health condition leads to **impairment** (loss or abnormality of body structure/function), which then restricts activities (**disability**), and ultimately impacts social roles (**handicap**). *Disease → Disability→Impairment→Handicap* - This order is incorrect because **impairment** (a problem in body function or structure) logically precedes **disability** (a difficulty executing tasks). - **Disability** arises from the *functional limitation* caused by impairment, not the other way around. *Disease → Disability→Handicap→Impairment* - This sequence is incorrect as **impairment** is the initial consequence of disease on a functional level, occurring before **disability** and **handicap**. - **Handicap** represents the societal and environmental disadvantage, which is the final stage in this classic WHO model. *Disease → Handicap→Impairment→Disability* - This order is incorrect because **handicap**, which refers to a social disadvantage, is the last step in the disablement process, following impairment and disability. - **Impairment** is a direct result of the disease, and **disability** follows from that impairment.

Q: Physical Quality of life consolidates which of the following indicators? 1. Infant Mortality Rate 2. Life expectancy at birth 3. Literacy 4. Per capita income 5. Mean years of schooling 6. Life expectancy at age one Select the correct answer using the code given below:

1, 3 and 6. ***1, 3 and 6*** - The **Physical Quality of Life Index (PQLI)** comprises **infant mortality rate**, **life expectancy at age one**, and **literacy rate**. - These indicators were selected to reflect basic human needs and well-being, independent of purely economic measures. *1, 2 and 3* - While **infant mortality rate** and **literacy** are part of PQLI, **life expectancy at birth** is not one of its three core components. - PQLI specifically uses **life expectancy at age one** to avoid the significant influence of high infant mortality on overall life expectancy at birth. *2, 3 and 6* - **Life expectancy at age one** and **literacy** are included in PQLI, but **life expectancy at birth** is not. - The PQLI's design intentionally focuses on outcomes after the critical first year of life. *1, 4 and 5* - **Infant mortality rate** is a PQLI component, but **per capita income** and **mean years of schooling** are not. - **Per capita income** is an economic indicator and explicitly excluded from PQLI, while **mean years of schooling** is more commonly associated with the Human Development Index (HDI).

Q: Disability-adjusted life years (DALYs) include:

Both YLL and YLD. ***Both YLL and YLD*** - **DALYs (Disability-Adjusted Life Years)** are a measure of overall disease burden, expressed as the number of years lost due to ill-health, disability, or early death. - They are calculated as the sum of **Years of Life Lost (YLL)** due to premature mortality and **Years Lost due to Disability (YLD)** for people living with a health condition or its consequences. *Neither YLL nor YLD* - This statement is incorrect because DALYs are explicitly designed to integrate both premature mortality (YLL) and the impact of non-fatal health outcomes (YLD). - Excluding both components would render DALYs meaningless as a comprehensive health metric. *Years lost to disability (YLD)* - While **YLD** is a crucial component of DALYs, focusing solely on YLD would ignore the impact of premature mortality. - A healthy life lost due to early death is as significant as years living with a disability in assessing disease burden. *Years of lost life (YLL)* - While **YLL** is an essential component, considering only YLL would overlook the burden of morbidity and disability. - Many chronic diseases cause significant disability and reduced quality of life without necessarily leading to premature death, which YLD accounts for.

Q: Consider the following data for a country: What shall be the dependency ratio of this country?

54.1 %. ***54.1 %*** - The **dependency ratio** measures the proportion of dependents (children 0-14 and elderly 65+) to the working-age population (15-64). - Calculation: ((391,558,367 + 71,943,390) / 856,076,200) × 100 = (463,501,757 / 856,076,200) × 100 = **54.14%**. *42.4 %* - This value is significantly **lower** than the calculated dependency ratio of 54.1%. - Would indicate a much smaller **dependent population** relative to the working-age group. *66.2 %* - This percentage is **higher** than the mathematically correct dependency ratio calculation. - Would suggest a larger proportion of **dependents** than actually exists in the given data. *78.6 %* - This value is significantly **overestimated** compared to the calculated dependency ratio. - Such a high ratio would indicate an unrealistic proportion of **non-working population** to working-age adults.

Q: Which one of the following is NOT a function of Epidemiology?

Making a clinical diagnosis. ***Making a clinical diagnosis*** - **Epidemiology** focuses on **population-level health patterns** and determinants of disease, not individual patient diagnosis. - Making a **clinical diagnosis** is the role of a healthcare provider based on a patient's symptoms, physical examination, and diagnostic tests. *Searching for the causes and risk factors* - A primary function of epidemiology is to **identify potential causes** and **risk factors** for diseases within populations. - This involves investigating associations between **exposures** and **health outcomes**. *Identifying syndromes* - Epidemiologists help identify new or unrecognized **patterns of disease** presentation that may constitute a **syndrome**. - This involves observing **clusters of symptoms** or conditions in a population. *To study historically the rise and fall of disease in the population* - **Historical epidemiology** tracks changes in disease incidence, prevalence, and mortality over time. - This function helps understand disease trends and the **impact of public health interventions**.

Q: In a cohort of 500 women attending antenatal clinic, 70 % had ultrasonography (USG). This cohort was followed up at delivery. Of the women who had USG, 70 delivered low birth weight (LBW) babies; whereas of the women, who did not undergo USG, 50 delivered LBW babies. The incidence of LBW babies among women who had USG is:

20 %. ***20 %*** - Total women are 500, and 70% had USG, which equals 350 women. - Of these 350 women, 70 delivered **low birth weight (LBW)** babies. Therefore, the incidence is (70/350) * 100% = **20%**. *25 %* - This option would imply a higher number of LBW babies among those who had USG than the actual data. - It does not align with the calculation based on the given figures (70 LBW babies out of 350 women who had USG). *10 %* - This option represents a lower incidence and does not correspond to the calculation of (70/350) * 100%. - This value might be obtained if the total number of women with USG was incorrectly assumed to be 700. *15 %* - This option is incorrect as it does not match the calculated incidence of LBW babies among women who underwent USG. - This would mean only 52.5 LBW babies were born, which contradicts the information given that 70 delivered LBW babies.

Question 1

The time period from entry of an infective agent into a host until the host develops the capacity for maximal infectivity is called:

Accepted Answer

Generation time

Answer

Incubation period

Answer

Period of communicability

Answer

Serial interval

Question 2

In a family of six (2 parents and 4 children), the youngest child catches measles infection. The parents are immune to the infection. On 3rd and 5th day of the infection of the first child, the two other children also suffer from measles. The secondary attack rate (SAR) of measles is:

Accepted Answer

66.6 %

Answer

40 %

Answer

50 %

Answer

33.3 %

Question 3

Standardized Mortality ratio is best explained by which one of the following statements?

Accepted Answer

Ratio of observed number of deaths to the expected number of deaths in a population

Answer

New spells of disease in a given period of time per 1000 population

Answer

Number of deaths in a given period of time per 1000 population

Answer

Percentage of deaths in women as compared to deaths in men

Question 4

Which one of the following statements is NOT true for taking a decision on screening for disease?

Accepted Answer

Proportion of false negatives is high

Answer

Sensitivity and specificity are high

Answer

Disease prevalence should be high

Answer

Disease is lethal

Question 5

The sequence of events leading to disability and handicap is:

Accepted Answer

Disease → Impairment→Disability→Handicap

Answer

Disease → Disability→Impairment→Handicap

Answer

Disease → Disability→Handicap→Impairment

Answer

Disease → Handicap→Impairment→Disability

Question 6

Physical Quality of life consolidates which of the following indicators?

1. Infant Mortality Rate
2. Life expectancy at birth
3. Literacy
4. Per capita income
5. Mean years of schooling
6. Life expectancy at age one

Select the correct answer using the code given below:

Accepted Answer

1, 3 and 6

Answer

1, 2 and 3

Answer

2, 3 and 6

Answer

1, 4 and 5

Question 7

Disability-adjusted life years (DALYs) include:

Accepted Answer

Both YLL and YLD

Answer

Neither YLL nor YLD

Answer

Years lost to disability (YLD)

Answer

Years of lost life (YLL)

Question 8

Consider the following data for a country: What shall be the dependency ratio of this country?

Accepted Answer

54.1 %

Answer

42.4 %

Answer

78.6 %

Answer

66.2 %

Question 9

Which one of the following is NOT a function of Epidemiology?

Accepted Answer

Making a clinical diagnosis

Answer

Searching for the causes and risk factors

Answer

Identifying syndromes

Answer

To study historically the rise and fall of disease in the population

Question 10

In a cohort of 500 women attending antenatal clinic, 70 % had ultrasonography (USG). This cohort was followed up at delivery. Of the women who had USG, 70 delivered low birth weight (LBW) babies; whereas of the women, who did not undergo USG, 50 delivered LBW babies. The incidence of LBW babies among women who had USG is:

Accepted Answer

20 %

Answer

25 %

Answer

10 %

Answer

15 %

Epidemiology — MCQs

Epidemiology — MCQs

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