Epidemiology Practice Questions

Q: Which one of the following statements regarding international classification of diseases, 10th revision (ICD-10) is not correct ?

It has twenty one major chapters. ***It has twenty one major chapters*** - ICD-10 actually consists of **22 chapters**, with chapter 22 (U00-U99) being designated for codes for special purposes like provisional assignment of new diseases. - Thus, the statement that it has twenty-one major chapters is **incorrect**. *First character of a code is a 'letter'* - In ICD-10, the first character of all codes is indeed a **letter**, which designates the chapter to which the code belongs. - This letter is followed by two numeric characters, forming the basic three-character category. *Each chapter has three character categories* - Each ICD-10 chapter is divided into **three-character categories**, which represent broadly defined diseases or conditions. - These categories can be further subdivided into more specific four-character or five-character codes. *It has three volumes* - The ICD-10 comprises **three volumes**: Volume 1 contains the main classification, Volume 2 provides instruction and guidance, and Volume 3 is the alphabetical index. - These volumes collectively offer a comprehensive system for disease coding and classification.

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: Other than cataract, which one among the following is the highest prevalent cause of blindness in the world ?

Glaucoma. ***Glaucoma*** - **Glaucoma** is the **second leading cause of blindness globally** after cataract, accounting for approximately 12-15% of all cases of blindness worldwide. - It is a group of eye conditions that damage the optic nerve, often due to elevated intraocular pressure, leading to **irreversible vision loss**. - Unlike cataract, glaucoma-induced blindness is **irreversible**, making it a major public health concern. - The prevalence is particularly high in older populations and varies by type (primary open-angle, angle-closure, etc.). *Corneal opacity* - **Corneal opacity** is an important cause of blindness, especially in developing countries, resulting from infections (corneal ulcers), trauma, vitamin A deficiency, and trachoma sequelae. - While significant, it accounts for approximately 4-5% of global blindness, ranking **below glaucoma** in overall prevalence. - Prevention through nutrition programs and timely treatment of infections has reduced its burden. *Trachoma* - **Trachoma**, caused by *Chlamydia trachomatis*, is a chronic keratoconjunctivitis and was historically a leading infectious cause of blindness. - Due to WHO's GET2020 (Global Elimination of Trachoma by 2020) initiative and SAFE strategy (Surgery, Antibiotics, Facial cleanliness, Environmental improvement), its prevalence has **declined significantly**. - It now accounts for less than 3% of global blindness. *Diabetic retinopathy* - **Diabetic retinopathy** is a growing cause of blindness, particularly in developed countries and among working-age adults, due to the diabetes epidemic. - It accounts for approximately 5% of global blindness. - While its prevalence is increasing, it remains **below glaucoma** as a cause of global blindness.

Q: The law stating that "the relative frequencies of each gene allele tend to remain constant from generation to generation" is known as

Hardy-Weinberg Law. ***Hardy-Weinberg Law*** - The **Hardy-Weinberg principle** states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences. - This law provides a baseline for understanding how populations evolve by identifying the conditions under which evolution *does not* occur. *Lamarck's Law* - **Lamarck's theory of inheritance of acquired characteristics** suggested that traits acquired during an organism's lifetime could be passed on to offspring. - This concept is largely disproven and not relevant to allele frequency constancy across generations. *David-Morgan's Law* - This is not a recognized law in genetics. There was a prominent geneticist named **Thomas Hunt Morgan**, whose work focused on fruit flies and established the **chromosome theory of inheritance** and concepts like linkage and crossing over. - While significant to genetics, his work does not describe the constancy of allele frequencies in a population. *Mendel's Law* - **Mendel's Laws of Inheritance** (segregation and independent assortment) describe how traits are passed from parents to offspring through the inheritance of discrete units (genes). - While fundamental to explaining inheritance, they do not directly state that allele frequencies remain constant in a population across generations under specific conditions, as the Hardy-Weinberg law does.

Q: Which one of the following is a correct combination regarding Indian population?

Blood group O 40%; Rh negative 7%. ***Blood group O 40%; Rh negative 7%*** - In the Indian population, **Blood group O** is indeed the most common, accounting for approximately **30-40%** of the population. - The prevalence of **Rh-negative** individuals in India is relatively low, typically around **5-7%**, making this combination accurate. *Blood group AB 20%; Rh negative 15%* - **Blood group AB** is the least common blood group, typically less than **10%** in the Indian population, making 20% an overestimation. - **Rh negative** prevalence of 15% is significantly higher than the reported figures for India, which are usually around 5-7%. *Blood group A 40%; Rh positive 80%* - While **Blood group A** is common, 40% might be slightly higher than some estimates, which often place it closer to 20-25%. - **Rh positive** prevalence in India is much higher than 80%, typically around **93-95%**, making 80% an underestimation. *Blood group B 33%; Rh positive 99%* - **Blood group B** is also very common in India, often around 30-35%, so 33% is a reasonable estimate. - However, **Rh positive** prevalence of 99% is an overestimation; the actual prevalence is closer to **93-95%**.

Q: Amniocentesis in early pregnancy for genetic disorders is a kind of

primary prevention. ***primary prevention*** - **Primary prevention** aims to *prevent disease from occurring* in the first place by reducing exposure to risk factors and preventing the birth of affected individuals - Amniocentesis in early pregnancy is a **prenatal diagnostic test** that detects genetic disorders in the fetus (who is at risk but not yet diseased) - The goal is to *prevent the occurrence* of genetic disease in the population by enabling informed reproductive decisions and preventing the birth of severely affected infants - This is classified as primary prevention because it **prevents the disease from manifesting** in the community *secondary prevention* - **Secondary prevention** focuses on *early detection and treatment* of disease in individuals who are already affected but asymptomatic - Examples include cancer screening (mammography, Pap smear), hypertension screening, and diabetes screening in adults - Amniocentesis is NOT secondary prevention because the fetus is not yet "diseased" – testing occurs before disease manifestation to prevent it *tertiary prevention* - **Tertiary prevention** aims to *reduce complications* and disability from established, symptomatic disease - Focuses on rehabilitation, preventing progression, and improving quality of life after disease has occurred - Examples include physiotherapy after stroke, insulin therapy for diabetes, and cardiac rehabilitation *primordial prevention* - **Primordial prevention** addresses *underlying determinants* of disease by preventing risk factors from developing in the population - Involves broad public health policies, environmental modifications, and socioeconomic interventions - Examples include tobacco control policies, promoting healthy urban design, and reducing environmental pollution

Q: The period of time required for the development of the parasite from the gametocyte to sporozoite stage in the body of the mosquito is about 10-20 days. This period is also referred to as

Extrinsic incubation period. ***Extrinsic incubation period*** - This term refers to the time taken for the **Plasmodium parasite** to develop from the **ingested gametocytes** to the **infective sporozoites** within the mosquito vector. - The duration of this period is typically 10-20 days, depending on the **species of Plasmodium** and environmental factors such as temperature. *Asexual cycle* - The asexual cycle, or **schizogony**, occurs within the human host, specifically in the **liver** (exoerythrocytic) and **red blood cells** (erythrocytic). - This cycle involves the multiplication of the parasite and is responsible for the clinical symptoms of malaria. *Schizogony* - **Schizogony** is a form of asexual reproduction characteristic of **apicomplexan parasites**, including Plasmodium. - It describes the process where a single parasitic cell (e.g., a **merozoite** or **sporozoite**) divides multiple times within a host cell to produce many daughter cells. *Erythrocytic cycle* - The **erythrocytic cycle** is a specific part of the human asexual cycle where **merozoites** infect red blood cells, multiply, and then lyse the cells to release more merozoites. - This cycle is responsible for the periodic fevers and other symptoms of malaria, but does not involve development within the mosquito.

Q: In a community with one lakh population, 20,000 slides were examined in a particular year. Out of these 100 were positive for malarial parasite. What is the Annual Parasite Incidence (API) in this community ?

1. ***Correct Answer: 1*** The **Annual Parasite Incidence (API)** is a key epidemiological indicator for malaria surveillance, defined as the number of **confirmed positive malaria cases per 1,000 population per year**. **Formula:** API = (Number of positive cases / Total population) × 1,000 **Calculation:** - Population = 1,00,000 (one lakh) - Positive cases = 100 - API = (100 / 1,00,000) × 1,000 = **1** The number of slides examined (20,000) is relevant for calculating the **Slide Positivity Rate (SPR)** but not directly used in the API calculation. *Incorrect: 2* - This would be correct if there were 200 positive cases in the same population - Represents double the actual API *Incorrect: 0.5* - This would be correct if there were only 50 positive cases in the population - Represents half the actual API *Incorrect: 5* - This would result from incorrectly using the number of slides examined (20,000) as the denominator instead of the total population (1,00,000) - Confuses SPR calculation methodology with API calculation

Q: Berksonian bias is a selection bias which occurs in

Hospital based studies. ***Hospital based studies*** - **Berksonian bias** is a type of **selection bias** that occurs when the study population is drawn from a hospital or clinical setting. - This can lead to an artificially inflated or deflated association between risk factors and diseases, as hospital patients often have multiple health conditions or risk factors not representative of the general population. *Natural exposure studies* - These studies observe populations exposed to a factor naturally, without intervention, and are less prone to selection bias related to hospital admission. - While other biases can occur, **Berksonian bias** specifically relates to admission criteria for healthcare facilities. *Community based studies* - **Community-based studies** aim to recruit participants from the general population, making them less susceptible to **Berksonian bias** compared to hospital-based studies. - They strive for a more representative sample, reducing the selection pressures seen in clinical settings. *Laboratory based studies* - **Laboratory studies** typically use controlled environments and experimental designs, often involving cell cultures or animal models. - They are generally not subject to **Berksonian bias**, which is specific to human population studies drawing from clinical settings.

Question 1

Which one of the following statements regarding international classification of diseases, 10th revision (ICD-10) is not correct ?

Accepted Answer

It has twenty one major chapters

Answer

First character of a code is a 'letter'

Answer

Each chapter has three character categories

Answer

It has three volumes

Question 2

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 3

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 4

Other than cataract, which one among the following is the highest prevalent cause of blindness in the world ?

Accepted Answer

Glaucoma

Answer

Trachoma

Answer

Corneal opacity

Answer

Diabetic retinopathy

Question 5

The law stating that "the relative frequencies of each gene allele tend to remain constant from generation to generation" is known as

Accepted Answer

Hardy-Weinberg Law

Answer

Lamarck's Law

Answer

David-Morgan's Law

Answer

Mendel's Law

Question 6

Which one of the following is a correct combination regarding Indian population?

Accepted Answer

Blood group O 40%; Rh negative 7%

Answer

Blood group AB 20%; Rh negative 15%

Answer

Blood group A 40%; Rh positive 80%

Answer

Blood group B 33%; Rh positive 99%

Question 7

Amniocentesis in early pregnancy for genetic disorders is a kind of

Accepted Answer

primary prevention

Answer

secondary prevention

Answer

tertiary prevention

Answer

primordial prevention

Question 8

The period of time required for the development of the parasite from the gametocyte to sporozoite stage in the body of the mosquito is about 10-20 days. This period is also referred to as

Accepted Answer

Extrinsic incubation period

Answer

Asexual cycle

Answer

Schizogony

Answer

Erythrocytic cycle

Question 9

In a community with one lakh population, 20,000 slides were examined in a particular year. Out of these 100 were positive for malarial parasite. What is the Annual Parasite Incidence (API) in this community ?

Accepted Answer

1

Answer

2

Answer

0.5

Answer

5

Question 10

Berksonian bias is a selection bias which occurs in

Accepted Answer

Hospital based studies

Answer

Natural exposure studies

Answer

Community based studies

Answer

Laboratory based studies

Epidemiology — MCQs

Epidemiology — MCQs

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