Epidemiology — MCQs
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Which of the following statements about incidence is false?
Spot map is used for?
A patient involved in a road traffic accident has undergone amputation of the right leg. What is the most appropriate term to describe this condition?
Which of the following is the primary component of the AFP (Acute Flaccid Paralysis) case definition used in polio surveillance?
Transovarian transmission is seen in-
What is a limitation of the case fatality rate?
Most common mode of transmission of nosocomial infection is -
Which statement best describes the concept of web of causation in disease?
Which of the following is not classified as a special incidence rate?
What is the best indicator of the availability, utilization, and effectiveness of health services?
Epidemiology Indian Medical PG Practice Questions and MCQs
Question 1781: Which of the following statements about incidence is false?
- A. Does not include unit of time (Correct Answer)
- B. It is a rate
- C. Numerator includes new cases
- D. Denominator includes population at risk
Explanation: ***Does not include unit of time*** - This statement is false because **incidence** is defined as the number of **new cases** of a disease over a specific period of time in a population at risk. - Therefore, it inherently includes a **unit of time** (e.g., per year, per month), making this option incorrect as a characteristic of incidence. *It is a rate* - **Incidence is a rate** because it quantifies the speed at which new cases of a disease occur within a population. - It expresses the number of new events (cases) per unit of population at risk over a specified time period. *Numerator includes new cases* - The **numerator of incidence** specifically counts the number of **new cases** of a disease that develop during a defined observation period. - This distinguishes it from prevalence, which includes all existing cases. *Denominator includes population at risk* - The **denominator for incidence** comprises the **population at risk** of developing the disease during the observation period. - Individuals who already have the disease or are immune are typically excluded from the denominator.
Question 1782: Spot map is used for?
- A. Local distribution of disease (Correct Answer)
- B. Rural-urban variation
- C. National variation
- D. None of the options
Explanation: ***Local distribution of disease*** - A **spot map** visually represents the geographic distribution of individual cases of a disease or health event. - Each 'spot' on the map corresponds to the exact location where a case occurred, making it ideal for identifying **clusters** or patterns of disease within a specific area. *Rural-urban variation* - While a spot map could potentially show cases in both rural and urban settings, its primary purpose is not to specifically highlight the differences between these two broad categories. - Other types of **thematic maps** or **statistical analyses** are better suited for assessing rural-urban variations. *National variation* - A spot map would be impractical for showing national variation in detail, as it would require plotting individual cases across an entire country, leading to an overly cluttered and uninterpretable image. - **Choropleth maps**, which use shading or colors to represent data for predefined geographic areas (like states or provinces), are more appropriate for illustrating national trends or variations. *None of the options* - This option is incorrect because the primary use of a spot map aligns directly with illustrating the **local distribution of disease**.
Question 1783: A patient involved in a road traffic accident has undergone amputation of the right leg. What is the most appropriate term to describe this condition?
- A. A pathological condition affecting the body.
- B. A limitation in performing daily activities.
- C. A social disadvantage resulting from an impairment.
- D. A loss of body structure or function. (Correct Answer)
Explanation: ***A loss of body structure or function*** (CORRECT - Definition of Impairment) - The amputation of a leg directly involves the **loss of a body structure** (the leg itself) and subsequently a loss of its function (e.g., ambulation). - This definition aligns with the WHO International Classification of Functioning, Disability and Health (ICF) framework's definition of **impairment**, which is a problem in body function or structure such as significant deviation or loss. - Amputation is a classic example of an impairment. *A pathological condition affecting the body* - While amputation results from a pathological process (trauma), the term **"pathological condition"** generally refers to the disease or injury itself (e.g., gangrene requiring amputation, or the trauma from the accident), not the direct consequence of the removal of a body part. - Amputation is a **treatment** or outcome of a pathological condition, rather than the condition itself in this context. *A limitation in performing daily activities* - This describes **"activity limitation"** (formerly termed "disability" in the old ICIDH classification), which is the consequence of an impairment at the level of the individual's activities. - While an amputee will experience limitations in daily activities, this term describes the functional impact, not the direct physical state of having lost a limb. *A social disadvantage resulting from an impairment* - This refers to **"participation restriction"** (formerly termed "handicap" in the old ICIDH classification), which is the disadvantage experienced by an individual as a result of an impairment or disability, acting as a barrier to fulfilling a social role. - This is a social and environmental concept, distinct from the direct physical loss of a body part.
Question 1784: Which of the following is the primary component of the AFP (Acute Flaccid Paralysis) case definition used in polio surveillance?
- A. All of the above
- B. Stool specimen positive for poliovirus
- C. Onset of acute flaccid paralysis (Correct Answer)
- D. Presence of residual paralysis after 60 days
Explanation: ***Onset of acute flaccid paralysis*** - The primary component of the **AFP case definition** for polio surveillance is the acute onset of **flaccid paralysis** in a child under 15 years, or paralytic illness in a person of any age when polio is suspected. - This definition is crucial for identifying all potential cases of polio, regardless of the cause, to ensure thorough investigation and prevent outbreaks. *Stool specimen positive for poliovirus* - A positive stool specimen for poliovirus is a **laboratory confirmation** of polio infection, but it is not the primary component of the initial case definition. - The AFP case definition aims for **high sensitivity** to capture all possible cases for investigation, even before laboratory results are available. *Presence of residual paralysis after 60 days* - Residual paralysis after 60 days is an important indicator for **classifying a confirmed polio case** and understanding the long-term impact. - However, it is a **follow-up criterion** used after the initial detection of AFP, not the primary component that triggers the initial surveillance. *All of the above* - While laboratory confirmation and residual paralysis provide further information about a case, the **initial identification relies specifically on the clinical presentation** of acute flaccid paralysis. - The broad clinical definition ensures that no potential polio case is missed, initiating an immediate public health response.
Question 1785: Transovarian transmission is seen in-
- A. Malaria
- B. Filaria
- C. Rickettsial diseases (Correct Answer)
- D. None of the options
Explanation: ***Rickettsial diseases*** - **Transovarian transmission** is a key mechanism for the maintenance and spread of **rickettsiae** in arthropod vectors. The bacteria can pass from an infected female arthropod (like a tick or mite) to her offspring via the eggs. - This ensures that the next generation of vectors is already infected and can transmit the disease, even without needing to acquire the pathogen from an infected vertebrate host. *Malaria* - Malaria is transmitted via the bite of an infected **Anopheles mosquito**, which acquires parasites from an infected human. - **Transovarian transmission** does not occur in malaria; mosquitoes are not born with the ability to transmit the parasite. *Filaria* - Filariasis is spread by various **mosquito vectors** (e.g., *Culex*, *Anopheles*, *Aedes*) or **black flies**, which acquire microfilariae from an infected host during a blood meal. - The parasite undergoes development within the insect, but **transovarian transmission** to the insect's offspring does not occur. *None of the options* - This option is incorrect because **rickettsial diseases** do exhibit transovarian transmission, making it a valid answer. - The phenomenon of passing pathogens directly from a female parent to her offspring via the egg is a specific mechanism seen in certain vector-borne diseases.
Question 1786: What is a limitation of the case fatality rate?
- A. Not useful in acute infectious disease
- B. Not related to virulence
- C. Time period not specified (Correct Answer)
- D. It is not related to survival rate
Explanation: ***Time period not specified*** - The **case fatality rate (CFR)** is sometimes presented without a clear time frame, making it difficult to compare across different studies or diseases. - A CFR calculated over **24 hours** is vastly different from one calculated over **30 days** or **one year**, yet both could be presented simply as "CFR" *Not useful in acute infectious disease* - The CFR is highly **useful** in acute infectious diseases, as it directly measures the **severity** and immediate impact of an outbreak. - It helps public health officials understand the **lethality** of an infectious agent and aids in resource allocation and intervention strategies. *Not related to virulence* - **Case fatality rate** is directly related to **virulence**, as it reflects the proportion of affected individuals who die from the disease. - A higher CFR indicates a more **virulent pathogen** or a more severe disease process. *It is not related to survival rate* - The **case fatality rate** is inherently linked to the **survival rate**; they are complementary measures. - If the CFR is X%, then the associated survival rate is (100 - X)%, representing the proportion of cases that do not die from the disease.
Question 1787: Most common mode of transmission of nosocomial infection is -
- A. Hand contact (Correct Answer)
- B. Droplet infection
- C. Blood and blood products
- D. Contaminated water
Explanation: ***Hand contact*** - **Direct contact** with healthcare workers' contaminated hands is the primary way pathogens are transferred between patients in a healthcare setting. - Failure to perform adequate **hand hygiene** between patient contacts is the single most important factor contributing to nosocomial infection transmission. *Droplet infection* - While droplet transmission can cause nosocomial infections, especially for respiratory viruses, it is not the most common mode of transmission for the overall burden of healthcare-associated infections. - **Droplets** usually travel short distances and deposit on mucous membranes of the nose, mouth, or eyes of a susceptible host. *Blood and blood products* - Transmission through **blood and blood products** is a significant concern for specific infections (e.g., HIV, hepatitis B/C), but the incidence is relatively low due to stringent screening and safety protocols. - This mode accounts for a small fraction of overall nosocomial infections compared to contact transmission. *Contaminated water* - **Contaminated water** can lead to outbreaks (e.g., *Legionella*, *Pseudomonas*), especially in immunocompromised patients, but it is not the most frequent mode of transmission on a day-to-day basis across all types of nosocomial infections. - Healthcare facilities implement measures to ensure water safety, limiting this as the primary route.
Question 1788: Which statement best describes the concept of web of causation in disease?
- A. Applicable primarily to common diseases.
- B. Focuses on epidemiological ratios.
- C. Aids in interrupting the transmission of diseases.
- D. Considers all relevant factors associated with disease causation. (Correct Answer)
Explanation: ***Considers all relevant factors associated with disease causation.*** - The **web of causation** model acknowledges that diseases often arise from a complex interplay of multiple interconnected factors, rather than a single cause. - It emphasizes that **no single factor is sufficient or necessary** for disease occurrence, but rather a combination of factors increases susceptibility or triggers the disease process. *Applicable primarily to common diseases.* - The web of causation model is a **universal concept** in epidemiology, applicable to both common and rare diseases. - Its utility lies in explaining the complex etiology of diseases regardless of their prevalence. *Focuses on epidemiological ratios.* - While epidemiological ratios (e.g., odds ratios, relative risk) measure associations between factors and disease, the **web of causation** provides a conceptual framework for understanding the *nature* of these associations. - It describes the **interconnections and causal pathways**, not just the statistical strength of association. *Aids in interrupting the transmission of diseases.* - This statement is more descriptive of **public health interventions** based on understanding disease transmission dynamics. - While insights from the **web of causation** can inform interventions, the model itself describes the *etiology* rather than directly outlining methods for interrupting transmission.
Question 1789: Which of the following is not classified as a special incidence rate?
- A. Attack rate
- B. Secondary attack rate
- C. Hospital admission rate
- D. Standardized mortality rate (Correct Answer)
Explanation: ***Standardized mortality rate*** - This is a measure used to compare **mortality rates** between different populations, adjusting for age or other confounding factors. - It is a **standardized mortality measure**, not an incidence rate, and therefore not classified as a special incidence rate. - Special incidence rates measure the occurrence of **new cases** in specific circumstances, whereas SMR is a **comparative mortality metric**. *Attack rate* - The **attack rate** is a classic **special incidence rate** used to describe the proportion of people in a population who became ill during an **epidemic or outbreak**. - It is specifically calculated during a **short, well-defined period**, often relevant to foodborne illnesses or infectious disease outbreaks. *Secondary attack rate* - The **secondary attack rate** is a **special incidence rate** that measures the proportion of susceptible people who develop a disease after being exposed to a **primary case** within a defined population (e.g., household contacts). - It quantifies the **spread of an infectious agent** within a closed population after its introduction. *Hospital admission rate* - This is a **health service utilization indicator** that measures hospital admissions in a population during a specified period. - It is **not classified as a special incidence rate** in standard epidemiological teaching, as it reflects healthcare utilization rather than disease occurrence in outbreak situations.
Question 1790: What is the best indicator of the availability, utilization, and effectiveness of health services?
- A. IMR (Correct Answer)
- B. MMR
- C. Hospital bed OCR
- D. DALY
Explanation: ***IMR*** - The **Infant Mortality Rate (IMR)** is widely considered the best single indicator of the availability, utilization, and effectiveness of health services because it reflects the health status of a population and the quality of prenatal, perinatal, and postnatal care. - A lower IMR generally indicates better access to maternal and child healthcare, nutrition, sanitation, and overall societal development. *MMR* - The **Maternal Mortality Ratio (MMR)** reflects the risk of maternal death relative to the number of live births and is a measure of the quality of maternal healthcare services. - While important, MMR focuses specifically on maternal health outcomes and does not encompass the broader availability and effectiveness of health services for all age groups as comprehensively as IMR. *Hospital bed OCR* - **Hospital bed occupancy rate (OCR)** indicates the proportion of available hospital beds that are occupied over a given period, reflecting the utilization of hospital resources. - While it offers insight into hospital efficiency and demand, it does not directly reflect the overall availability, effectiveness, or quality of primary care, preventive services, or broader public health interventions. *DALY* - **Disability-Adjusted Life Years (DALY)** measure the total number of healthy life years lost due to premature mortality and disability from disease or injury. - DALYs provide a comprehensive measure of disease burden but are more focused on quantifying the impact of diseases and injuries on health than on directly assessing the availability, utilization, and effectiveness of health services themselves.
Practice by Chapter
Principles of Epidemiology
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Measures of Disease Frequency
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Epidemiological Study Designs
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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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