Epidemiology — MCQs

Epidemiology Indian Medical PG Practice Questions and MCQs

Question 1801: Which study design is considered the most effective for establishing a definitive causal relationship in epidemiological research?

A. Case-control study
B. Randomized controlled trial (Correct Answer)
C. Ecological study
D. Cross-sectional study

Explanation: ***Randomized controlled trial*** - **Random allocation** minimizes confounding, ensuring that groups are comparable at baseline, which allows for a more definitive assessment of the intervention's effect. - The prospective nature and controlled environment of an RCT enable direct measurement and comparison of outcomes between the intervention and control groups, thereby strengthening the evidence for a **causal relationship**. - RCTs provide the **highest level of evidence** in the hierarchy of study designs for establishing causation. *Case-control study* - This design is **retrospective**, looking back in time to identify exposures after an outcome has occurred, making it prone to **recall bias** regarding past exposures. - While useful for studying rare diseases, it cannot establish temporality unequivocally, which is crucial for inferring causation. *Ecological study* - This study design analyzes data at the **population level** rather than the individual level, making it susceptible to the **ecological fallacy** (attributing group characteristics to individuals). - It cannot directly link exposure to outcome in individuals and is primarily used for generating hypotheses, not establishing causation. *Cross-sectional study* - This design measures exposure and outcome simultaneously at a **single point in time**, which makes it impossible to determine the temporal sequence of events. - Its inability to establish **temporality** means it cannot definitively determine whether the exposure preceded the outcome, a fundamental requirement for causality.

Question 1802: The study of human diseases and their impact on society is known as?

A. Public health
B. Epidemiology (Correct Answer)
C. Health sociology
D. Medical anthropology

Explanation: ***Epidemiology*** - **Epidemiology** is defined as the study of the distribution, determinants, patterns, and frequency of health and disease conditions in defined populations, including their **impact on society**. - It is the fundamental science of **public health** that specifically studies how diseases affect populations and society through systematic investigation using statistical and analytical methods. - Epidemiological studies directly examine disease burden, mortality, morbidity, and societal impact, making it the most precise answer for studying diseases and their societal consequences. - Key epidemiological measures (incidence, prevalence, DALYs) quantify the **societal impact** of diseases. *Public health* - **Public health** is the broader applied field that uses epidemiological findings to implement programs, policies, and interventions. - While public health addresses disease impact, it is primarily an **action-oriented discipline** focused on prevention and health promotion, not just the study of diseases. - Public health encompasses multiple disciplines including epidemiology, health education, environmental health, and health policy. *Health sociology* - **Health sociology** (or medical sociology) examines social factors, behaviors, and structures that influence health outcomes and healthcare access. - It focuses on social determinants, health inequalities, and illness behavior from a **sociological perspective**, rather than the scientific study of disease distribution and patterns. *Medical anthropology* - **Medical anthropology** studies health, illness, and healing through a **cultural and ethnographic lens**. - It examines how different cultures understand disease, healing practices, and medical systems, rather than studying disease patterns and their population-level impact.

Question 1803: Which method is primarily used to assess HIV prevalence?

A. Sentinel surveillance in high-risk populations (Correct Answer)
B. Passive surveillance through reporting systems
C. Disease registries for HIV patients
D. Active case finding through outreach programs

Explanation: ***Sentinel surveillance in high-risk populations*** - **Sentinel surveillance** focuses on specific, well-defined groups, such as pregnant women or individuals attending STD clinics, to get a representative estimate of **HIV prevalence** in the broader community. - This method is particularly effective for diseases that are difficult to track through general population surveys due to stigma or low overall prevalence. *Passive surveillance through reporting systems* - **Passive surveillance** relies on healthcare providers voluntarily reporting cases, which often leads to **underreporting** and an incomplete picture of an epidemic's true scope. - It primarily captures known cases rather than estimating the overall **prevalence** within a population. *Disease registries for HIV patients* - **Disease registries** are valuable for tracking the natural history, treatment outcomes, and long-term trends among *diagnosed* individuals, but they do not capture undiagnosed cases, thus not accurately representing **prevalence**. - They provide data on incidence (new cases) and patient management but are less suited for estimating the total number of people living with the disease at a given time. *Active case finding through outreach programs* - **Active case finding** aims to identify new cases within specific communities, usually in response to an outbreak or in populations with known high risk. - While it identifies undiagnosed individuals, its primary goal is case identification and linkage to care, rather than providing a **statistically representative prevalence** estimate for an entire population.

Question 1804: What is the most common cancer diagnosed in men?

A. Bladder cancer
B. Colorectal cancer
C. Oral cancer (Correct Answer)
D. Prostate cancer

Explanation: ***Oral cancer*** - **Oral cancer** is the most common cancer diagnosed in men in India, particularly cancers of the **lip, oral cavity, and oropharynx**. - India accounts for approximately **one-third of the global burden** of oral cancers. - Major risk factors include **tobacco chewing (gutka, pan masala, betel quid), smoking, and alcohol consumption**. - Early detection through **oral examination** and avoiding tobacco products are key preventive measures. *Prostate cancer* - While prostate cancer is the most common cancer in men in **Western populations**, it ranks **much lower in India** (typically 3rd-5th most common). - Incidence is increasing in urban Indian populations due to improved detection and lifestyle changes. *Bladder cancer* - **Bladder cancer** is significant but less common than oral cancer in Indian men. - Risk factors include **smoking** and occupational exposure to chemicals. *Colorectal cancer* - **Colorectal cancer** is increasing in incidence in India but remains less common than oral cancer in men. - Screening with **colonoscopy** is recommended for early detection, especially in those with family history.

Question 1805: Which cancer type has the most effective screening procedure?

A. Prostate Cancer
B. Colon Cancer
C. Cervical Cancer (Correct Answer)
D. Gastric Cancer

Explanation: ***Cervical Cancer*** - **Pap smear and HPV testing** represent the most effective cancer screening program, with proven reduction of **>70% in cervical cancer incidence and mortality**. - Screening detects **pre-cancerous lesions (CIN)** during the long latent period, allowing for effective intervention before cancer develops. - Well-established guidelines with high sensitivity, specificity, and cost-effectiveness make it a **public health success story**. - Particularly relevant in Indian context where cervical cancer burden is high and screening programs are being expanded. *Colon Cancer* - **Colonoscopy** and **fecal occult blood testing (FOBT)** are highly effective, allowing direct visualization and removal of precancerous polyps. - While very effective with proven mortality reduction, screening uptake is lower and the procedure is more invasive than cervical cancer screening. - Effectiveness is comparable but cervical cancer screening has achieved greater population-level impact historically. *Prostate Cancer* - Screening with **PSA (prostate-specific antigen) testing** and **digital rectal exam (DRE)** is controversial due to potential for **overdiagnosis and overtreatment** of indolent cancers. - Impact on overall mortality reduction is debated, and it doesn't prevent cancer through detection of precancerous lesions like cervical/colon cancer screening. *Gastric Cancer* - **Gastric cancer screening** is not routinely recommended in most countries including India due to lower prevalence and lack of a highly effective, non-invasive screening method. - **Endoscopy** can detect gastric cancer but is typically performed in symptomatic individuals or high-risk populations (e.g., Japan, Korea), not as a general population screening tool.

Question 1806: Who is often referred to as the 'Father of Modern Epidemiology'?

A. Edwin Chadwick
B. Lemuel Shattuck
C. Robert Koch
D. John Snow (Correct Answer)

Explanation: ***John Snow*** - **John Snow** is widely recognized as the **"Father of Modern Epidemiology"** for his groundbreaking work in identifying the source of the 1854 **Broad Street cholera outbreak** in London. - He used epidemiological methods like **dot maps** and **cohort analysis** to trace the outbreak to a contaminated water pump, establishing the **waterborne transmission** of cholera. *Edwin Chadwick* - Edwin Chadwick was a key figure in the **public health reform movement** in 19th-century Britain, advocating for improved sanitation and living conditions. - While significant, his work was focused on **social reform and sanitation infrastructure** rather than developing the scientific methods of epidemiology. *Lemuel Shattuck* - Lemuel Shattuck was an American statistician and public health reformer known for his 1850 report on the sanitary conditions of Massachusetts. - His work was influential in establishing a **public health infrastructure** in the United States, but he is not credited with founding modern epidemiological methods. *Robert Koch* - Robert Koch was a German physician and microbiologist renowned for his contributions to the field of **bacteriology**, particularly for identifying the specific causative agents of diseases like **anthrax, tuberculosis, and cholera**. - While his work was crucial for understanding infectious diseases, his primary focus was on **microbiology and germ theory**, not the ecological and population-level study of disease distribution that characterizes epidemiology.

Question 1807: Which of the following best describes the concept where a suspected cause precedes the observed effect?

A. Temporal association (Correct Answer)
B. Consistency of association
C. Strength of association
D. Coherence of association

Explanation: ***Temporal association*** - This principle in **causal inference** emphasizes that for a factor to be a cause, it must precede the effect. - In epidemiology, it's crucial to establish that exposure occurred **before the disease manifestation**. *Consistency of association* - Refers to the observation of a **similar association across different studies** and populations. - While important for causal inference, it does not directly address the timing of cause and effect. *Strength of association* - Quantifies how often the **exposure and outcome co-occur**, often measured by relative risk or odds ratio. - A strong association is more likely to be causal, but it doesn't confirm that the cause came before the effect. *Coherence of association* - Implies that the observed association should be **consistent with existing biological and medical knowledge**. - This criterion supports the plausibility of an association but doesn't specifically deal with the temporal sequence.

Question 1808: All of the following are characteristics of case control study except:

A. Quick results are obtained
B. Measures incidence rate (Correct Answer)
C. Inexpensive study
D. Proceeds from effect to cause

Explanation: ***Correct: Measures incidence rate*** - A **case-control study** proceeds from effect (disease) to cause (exposure) and thus does **NOT measure the incidence rate** of a disease. - Case-control studies calculate **odds ratios**, not incidence rates. - **Incidence rate** is typically measured in **cohort studies**, where a group of individuals is followed over time to observe the development of new cases of a disease. *Incorrect: Quick results are obtained* - Case-control studies are generally **retrospective**, meaning they look back in time from the outcome (disease) to identify past exposures. - This design allows for **quicker data collection** and analysis compared to prospective studies like cohort studies, which follow individuals over time. - This IS a characteristic of case-control studies. *Incorrect: Proceeds from effect to cause* - In a case-control study, researchers start by identifying individuals with the **disease (cases)** and a comparable group without the disease (controls). - They then investigate past exposures in both groups to determine potential **risk factors** or causes. - This IS a characteristic of case-control studies. *Incorrect: Inexpensive study* - Case-control studies are typically **less expensive** than other analytical study designs, such as cohort studies. - This is because they do not require long-term follow-up of a large population, reducing costs associated with repeated measurements and participant retention. - This IS a characteristic of case-control studies.

Question 1809: What is the structure of the ICD-10 classification system?

A. Consists of 21 chapters
B. Revised every 10 years
C. Arranged in 3 volumes (Correct Answer)
D. Produced by the World Health Organization

Explanation: ***Arranged in 3 volumes*** - The **ICD-10 classification system** is traditionally published in **three volumes** for ease of use. - **Volume 1** lists diseases alphabetically, **Volume 2** provides instructional and guidelines, and **Volume 3** has an alphanumeric index. *Revised every 10 years* - ICD classifications are revised periodically, but there is **no fixed 10-year revision cycle**; updates occur as needed. - For instance, ICD-9 was in use for many decades before ICD-10 and then ICD-11 was released significantly later. *Consists of 22 chapters* - The ICD-10 classification system is organized into **21 chapters**, each covering a specific range of diseases or health problems. - These chapters categorize diseases and conditions based on criteria such as etiology, body system, or type of injury. *Produced by the World Health Organization* - The **World Health Organization (WHO)** is indeed responsible for developing and maintaining the ICD system. - However, this option describes the **originator** of the system, not its structural arrangement.

Question 1810: Which of the following is not an indicator for malaria surveillance in a population?

A. Annual parasite index
B. Hemoglobin level (Correct Answer)
C. Annual parasite incidence
D. Annual falciparum incidence

Explanation: ***Hemoglobin level*** - While **anemia** (low hemoglobin) is a common complication and clinical consequence of malaria infection, **hemoglobin level is NOT a direct indicator used for malaria surveillance** in a population. - Anemia has multiple etiologies including nutritional deficiencies (iron, folate, B12), chronic diseases, hemoglobinopathies, and other infections - making it a non-specific parameter. - Malaria surveillance requires **specific indicators** that directly measure malaria transmission and disease burden, not secondary clinical consequences. *Incorrect: Annual Parasite Index (API)* - **Annual Parasite Index (API)** is a key malaria surveillance indicator that measures the number of **confirmed malaria cases per 1,000 population per year**. - API is calculated as: (Total positive blood smears / Total population) × 1,000 - API < 1 per 1,000 population is a benchmark target for malaria elimination programs. - Note: API is also called "Annual Parasite Incidence" - these terms are synonymous in current usage. *Incorrect: Annual Parasite Incidence* - **Annual Parasite Incidence** is the same indicator as Annual Parasite Index (API) - the terminology has evolved but both refer to confirmed malaria cases per 1,000 population per year. - This is the **most important single indicator** for monitoring malaria burden and evaluating control program effectiveness. - Used by WHO and National Vector Borne Disease Control Programme (NVBDCP) for malaria surveillance. *Incorrect: Annual Falciparum Incidence (AFI)* - **Annual Falciparum Incidence (AFI)** specifically measures the incidence of ***Plasmodium falciparum*** malaria cases per 1,000 population per year. - This is a critical surveillance indicator because P. falciparum causes the most severe disease with highest mortality. - AFI helps target interventions against the most dangerous malaria species and track progress in reducing malaria-related deaths. - Calculated as: (Total P. falciparum positive cases / Total population) × 1,000

Practice by Chapter

Principles of Epidemiology

Practice Questions

Measures of Disease Frequency

Practice Questions

Epidemiological Study Designs

Practice Questions

Descriptive Epidemiology

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Analytical Epidemiology

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Experimental Epidemiology

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Screening for Disease

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Surveillance Systems

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Investigation of an Epidemic

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Association and Causation

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Modern Epidemiological Methods

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Critical Appraisal of Epidemiological Studies

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