Epidemiology Practice Questions

Q: How many volumes are there in the ICD-10 classification system?

3. **Explanation** The **International Classification of Diseases, 10th Revision (ICD-10)** is a diagnostic tool maintained by the WHO for epidemiological, health management, and clinical purposes. It is structured into **three distinct volumes**, each serving a specific function: 1. **Volume 1 (Tabular List):** Contains the main classification itself. It consists of an alphanumeric list of diseases and conditions organized into 21 chapters. 2. **Volume 2 (Instruction Manual):** Provides the rules, guidelines, and historical background for coding and recording. It ensures international uniformity in data collection. 3. **Volume 3 (Alphabetical Index):** An exhaustive index of the diseases and conditions found in Volume 1, used by coders to locate the correct alphanumeric code. **Analysis of Options:** * **Option A & B (1 or 2):** These are incorrect as they do not account for the full structural framework required for standardized global coding (Classification + Rules + Index). * **Option D (4):** While some countries have developed "Clinical Modifications" (like ICD-10-CM) which may have additional sub-parts, the standard WHO ICD-10 system is strictly comprised of three volumes. **High-Yield Clinical Pearls for NEET-PG:** * **ICD-11 Update:** Note that ICD-11 came into effect globally on **January 1, 2022**. It is fully digital and no longer strictly defined by "volumes" in the traditional printed sense. * **Coding Structure:** ICD-10 uses an **alphanumeric code** (e.g., A00.0), where the first character is a letter. * **Purpose:** It is the standard for "Mortality and Morbidity" statistics worldwide.

Q: Screening tests can yield a high rate of false positives if they satisfy which of the following epidemiological parameters?

Low prevalence. **Explanation:** The number of false positives in a screening program is primarily determined by the **Positive Predictive Value (PPV)**, which is heavily influenced by the **prevalence** of the disease in the population. **1. Why Low Prevalence is Correct:** PPV is the probability that a person with a positive test result actually has the disease. Mathematically, as prevalence decreases, the PPV also decreases. In a low-prevalence population (e.g., screening a rare disease in the general public), the vast majority of people are healthy. Even a highly specific test will encounter so many healthy individuals that the absolute number of "false positives" will eventually outweigh the "true positives." Therefore, screening in low-prevalence settings yields a high rate of false positives. **2. Why Other Options are Incorrect:** * **High Specificity:** Specificity is the ability of a test to correctly identify those without the disease. High specificity actually *reduces* the number of false positives. * **High Sensitivity:** Sensitivity is the ability to identify true cases. While high sensitivity minimizes false negatives, it does not directly cause high false positives (that is a function of low specificity). * **High Prevalence:** In a high-prevalence setting (e.g., a TB clinic), a positive test is much more likely to be a true positive, thereby increasing the PPV and reducing the relative rate of false positives. **High-Yield Clinical Pearls for NEET-PG:** * **Prevalence vs. Predictive Value:** Prevalence is directly proportional to PPV and inversely proportional to Negative Predictive Value (NPV). * **Screening Strategy:** To minimize false positives, screening should be targeted at "high-risk groups" (increasing the effective prevalence). * **Sequential Testing:** Using a second, more specific test after a positive screening result is a common clinical strategy to eliminate the false positives generated in low-prevalence settings.

Q: In the Sample Registration System, an independent survey is done at every?

6 months. **Explanation:** The **Sample Registration System (SRS)** is a large-scale demographic survey in India used to provide reliable annual estimates of birth rates, death rates, and other fertility/mortality indicators. It is based on a **Dual Record System** to ensure maximum accuracy and minimize under-reporting. 1. **Continuous Enumeration:** A resident part-time enumerator (usually a teacher or Anganwadi worker) records births and deaths as they occur in a specific sample unit. 2. **Independent Retrospective Survey:** Every **6 months**, a full-time supervisor (from the Census department) conducts an independent survey to record events that occurred during the previous half-year. The data from both sources are then matched, and any discrepancies are field-verified. This "half-yearly" check is the hallmark of the SRS, making **Option B** the correct answer. **Why other options are incorrect:** * **A (2 months):** This interval is too frequent and logistically impractical for a national-scale survey. * **C & D (12 months / 2 years):** Waiting a year or more increases the risk of **recall bias**, where residents forget to report vital events (especially neonatal deaths), leading to underestimation of rates. **High-Yield Pearls for NEET-PG:** * **Gold Standard:** SRS is the most reliable source of **Vital Statistics** (IMR, MMR, CBR) in India, unlike the Civil Registration System (CRS), which suffers from under-registration. * **Initiation:** SRS was started on a pilot basis in 1964-65 and became fully operational in **1969-70**. * **Authority:** It is conducted by the **Registrar General of India (RGI)**, Ministry of Home Affairs. * **Sample Unit:** The sample unit in rural areas is a village (or segment), and in urban areas, an enumeration block.

Q: The iceberg phenomenon is not seen in which of the following diseases?

Measles. ### Explanation The **Iceberg Phenomenon of Disease** describes a situation where only a small fraction of the total cases in a community are visible (diagnosed/symptomatic), while a large, submerged portion represents undiagnosed, subclinical, or carrier states. **Why Measles is the Correct Answer:** Measles is a classic example of a disease that **does not** show the iceberg phenomenon. It is highly infectious and clinically apparent; almost every infected individual develops the characteristic rash and symptoms. Therefore, there are virtually no "submerged" subclinical cases or chronic carriers. Other diseases that do not show this phenomenon include **Rabies** and **Tetanus**. **Analysis of Incorrect Options:** * **AIDS (HIV):** Shows a massive iceberg phenomenon. The "tip" represents patients with clinical AIDS, while the "submerged portion" consists of a large number of asymptomatic HIV-positive individuals who can still transmit the virus. * **Tuberculosis (TB):** A significant iceberg disease. For every active case of TB (tip), there are numerous individuals with latent TB infection (submerged) who are asymptomatic but harbor the bacteria. * **Poliomyelitis:** This is the **classic textbook example** of the iceberg phenomenon. For every one paralytic case (tip), there are hundreds of subclinical/inapparent infections (submerged) that contribute to the spread of the virus. **NEET-PG High-Yield Pearls:** 1. **The Tip:** Represents what the clinician sees (symptomatic cases/diagnosed cases). 2. **The Submerged Portion:** Represents what the epidemiologist seeks (subclinical, latent, undiagnosed cases, and carriers). 3. **The Waterline:** Represents the demarcation between apparent and inapparent disease. 4. **Screening** is most useful for diseases that exhibit the iceberg phenomenon to identify the submerged cases.

Q: Which of the following is a cause of pandemics?

Influenza A. **Explanation:** The correct answer is **Influenza A**. The primary reason Influenza A causes pandemics is its unique ability to undergo **Antigenic Shift**. This involves a major genetic recombination (reassortment) resulting in a completely new subtype of the Hemagglutinin (H) or Neuraminidase (N) surface antigens. Because the global population has no pre-existing immunity to these new subtypes, the virus spreads rapidly across continents, leading to a pandemic. **Analysis of Options:** * **Influenza B:** Unlike Influenza A, which infects both humans and animals (birds/pigs), Influenza B primarily infects humans. It only undergoes **Antigenic Drift** (minor point mutations), leading to seasonal epidemics rather than global pandemics. * **Hepatitis B:** This is a blood-borne/sexually transmitted infection. While it is a major global health burden (endemic in many regions), it does not possess the rapid respiratory transmission or sudden antigenic shifts required to trigger a "pandemic" in the classical epidemiological sense. * **Cholera:** While Cholera can cause widespread outbreaks and has historically caused seven global pandemics, it is primarily **water-borne**. In modern epidemiology, the term "pandemic" is most characteristically associated with the rapid, airborne spread of novel respiratory viruses like Influenza A. **High-Yield Pearls for NEET-PG:** * **Antigenic Shift:** Major change, occurs only in Influenza A, leads to **Pandemics**. * **Antigenic Drift:** Minor change, occurs in both Influenza A and B, leads to **Epidemics**. * **Pandemic Criteria:** Must be a new disease (to the population), infect humans causing serious illness, and spread easily and sustainably among humans on a global scale. * **Historical Note:** The H1N1 Spanish Flu (1918) and the 2009 Swine Flu are classic examples of Influenza A pandemics.

Q: Which of the following is a component of the Human Development Index?

Life expectancy at birth. **Explanation:** The **Human Development Index (HDI)** is a composite statistical tool used by the UNDP to measure a country's overall achievement in its social and economic dimensions. It is based on three key dimensions, each represented by specific indicators: 1. **Health (Longevity):** Measured by **Life expectancy at birth**. This is the correct answer. 2. **Education (Knowledge):** Measured by Mean years of schooling (for adults) and Expected years of schooling (for children). 3. **Standard of Living:** Measured by Gross National Income (GNI) per capita (PPP $). **Analysis of Incorrect Options:** * **Maternal Mortality Rate (A):** While a critical health indicator, it is used in the *Gender Inequality Index (GII)*, not the HDI. * **Infant Mortality Rate (B):** This is a sensitive indicator of socio-economic development and healthcare quality, but it is a component of the **Physical Quality of Life Index (PQLI)**, not the HDI. * **Life expectancy at 1 year (D):** This is the specific health indicator used in the **PQLI**. The HDI specifically uses life expectancy at *birth*. **High-Yield Pearls for NEET-PG:** * **HDI vs. PQLI:** HDI includes income (GNI), whereas PQLI does not. PQLI components are Infant Mortality Rate, Life Expectancy at Age 1, and Literacy. * **HDI Range:** Values range from 0 to 1. A score of $\geq$ 0.800 is considered "Very High Human Development." * **Goalposts:** For calculating the Life Expectancy Index, the minimum value is 20 years and the maximum is 85 years.

Q: Which of the following statements is NOT true regarding cohort studies?

The odds ratio can be calculated from a cohort study.. ### Explanation In epidemiology, the primary measure of association for a **Cohort Study** is the **Relative Risk (RR)** or Incidence Study, not the Odds Ratio. **1. Why Option C is the correct answer (The False Statement):** The **Odds Ratio (OR)** is the characteristic measure of association for **Case-Control studies**. While it is mathematically possible to calculate an odds ratio from a 2x2 table in a cohort study, it is not the standard or intended measure. Cohort studies allow for the direct calculation of **Incidence**, which makes **Relative Risk (RR)** and **Attributable Risk (AR)** the appropriate measures to determine the strength of association. **2. Analysis of Incorrect Options:** * **Option A:** Cohort studies are the "gold standard" of observational designs for establishing **temporality** (exposure precedes disease), making them highly reliable for showing associations. * **Option B:** While most cohort studies are prospective, **Retrospective (Historical) Cohort studies** are common. They use past records (e.g., occupational health logs) to identify exposure and follow the timeline forward to the present. * **Option D:** In a cohort study, the investigator starts with known exposed and non-exposed groups. Therefore, the **Incidence (rate of new cases)** can be calculated for both groups, which is a defining feature of this study design. ### High-Yield Clinical Pearls for NEET-PG: * **Cohort Study:** Starts with **Cause** and moves to **Effect**. Best for rare exposures. * **Case-Control Study:** Starts with **Effect** and moves to **Cause**. Best for rare diseases. * **Relative Risk (RR):** Incidence among exposed / Incidence among non-exposed. * **Odds Ratio (OR):** Cross-product ratio (ad/bc). If a disease is rare, OR approximates RR. * **Mnemonic:** **C**ohort = **I**ncidence (**CI**); **C**ase-Control = **O**dds Ratio (**CO**).

Question 1

How many volumes are there in the ICD-10 classification system?

Accepted Answer

3

Answer

1

Answer

2

Answer

4

Question 2

Screening tests can yield a high rate of false positives if they satisfy which of the following epidemiological parameters?

Accepted Answer

Low prevalence

Answer

High specificity

Answer

High sensitivity

Answer

High prevalence

Question 3

Which of the following statements regarding vaccine sensitivity is FALSE?

Accepted Answer

Tetanus vaccine is most heat sensitive.

Answer

BCG and measles vaccines are sensitive to light.

Answer

Hepatitis B vaccine is sensitive to freezing.

Answer

Polio vaccine is most sensitive to heat.

Question 4

In the Sample Registration System, an independent survey is done at every?

Accepted Answer

6 months

Answer

2 months

Answer

12 months

Answer

2 years

Question 5

What is the definition of Net Reproductive Rate (NRR)?

Accepted Answer

Number of daughters a woman is expected to bear during her reproductive years

Answer

Total number of children in a family

Answer

Total number of members in a family

Answer

Total number of female children in a family

Question 6

Post-exposure active immunity should be administered in all situations EXCEPT?

Accepted Answer

Measles

Answer

Tetanus

Answer

Rabies

Answer

Hepatitis B

Question 7

The iceberg phenomenon is not seen in which of the following diseases?

Accepted Answer

Measles

Answer

AIDS

Answer

TB

Answer

Poliomyelitis

Question 8

Which of the following is a cause of pandemics?

Accepted Answer

Influenza A

Answer

Hepatitis B

Answer

Influenza B

Answer

Cholera

Question 9

Which of the following is a component of the Human Development Index?

Accepted Answer

Life expectancy at birth

Answer

Maternal mortality rate

Answer

Infant mortality rate

Answer

Life expectancy at 1 year

Question 10

Which of the following statements is NOT true regarding cohort studies?

Accepted Answer

The odds ratio can be calculated from a cohort study.

Answer

They are a reliable method for showing an association between a suspected risk factor and subsequent disease.

Answer

They can be designed as either retrospective or prospective studies.

Answer

Exposure rates can be calculated from a cohort study.

Epidemiology — MCQs

Epidemiology — MCQs

On this page

Practice by Chapter

Want unlimited practice?