Epidemiology — MCQs
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What is the prevalence of Rheumatic Heart Disease (RHD) in India in the 5-15 years age group based on school-based screening studies?
What is the primary purpose of taking sewer swabs in public health?
What is the most common nosocomial infection?
Which group classification does a state belong to if the prevalence of HIV infection in antenatal women is reported to be less than 1% and in high-risk populations is reported to be less than 5%?
Under which condition is screening IMPOSSIBLE (most fundamental criterion)?
Cluster testing technique is useful in which of the following conditions?
Which method is primarily used to detect cases that may not be identified through other surveillance techniques?
What is the criterion for blindness as defined in India?
Case-control study is an example of?
NFHS-3 was conducted in?
Epidemiology Indian Medical PG Practice Questions and MCQs
Question 1721: What is the prevalence of Rheumatic Heart Disease (RHD) in India in the 5-15 years age group based on school-based screening studies?
- A. 1-2 per 1000
- B. 5-7 per 1000 (Correct Answer)
- C. 10-12 per 1000
- D. 13-15 per 1000
Explanation: ***Correct: 5-7 per 1000*** - School-based screening studies focusing on the 5-15 years age group in India reveal a prevalence of **rheumatic heart disease (RHD)** ranging from **5 to 7 per 1000** children. - This prevalence highlights the significant public health burden of RHD within this vulnerable age demographic in India. - Multiple echocardiographic screening studies across different regions of India consistently report this range as the average prevalence. *Incorrect: 1-2 per 1000* - This range is generally considered too low for the true prevalence of RHD in school-aged children in India, as documented by multiple studies. - It might represent prevalence rates in regions with very strong primary prevention programs or different demographic groups. - Underestimates the actual disease burden in the Indian context. *Incorrect: 10-12 per 1000* - While higher than the actual average, this range is typically considered an overestimate for the general prevalence of RHD in this age group from school-based screenings in India. - Such high numbers might be seen in extremely high-risk or specific endemic areas but do not represent the national average. *Incorrect: 13-15 per 1000* - This range is significantly higher than the reported average prevalence of RHD in school-based screening studies in India. - This would indicate an alarmingly widespread and uncontrolled incidence of RHD, which is not supported by current epidemiological data. - May represent historical data from decades ago or specific high-risk pockets rather than current national estimates.
Question 1722: What is the primary purpose of taking sewer swabs in public health?
- A. Active typhoid cases in the community
- B. Active cholera cases in the community
- C. Typhoid carriers in the community (Correct Answer)
- D. Cholera carriers in the community
Explanation: ***Typhoid carriers in the community*** - Sewer swabs are primarily used to detect the presence of **Salmonella Typhi** in sewage, indicating the presence of **asymptomatic carriers** shedding the bacteria. - This method helps identify populations where **typhoid fever** may silently spread or persist due to chronic carriers. *Active typhoid cases in the community* - While sewer swabs can indirectly indicate **active cases** due to increased shedding, their primary purpose is to identify **carriers** who might not be exhibiting symptoms. - **Clinical diagnosis** and **stool culture** from symptomatic individuals are more direct methods for identifying active typhoid cases. *Active cholera cases in the community* - Sewer swabs *can* detect **Vibrio cholerae**, the bacterium causing cholera, but this is not their primary use, especially when targeting **typhoid surveillance**. - **Cholera** outbreaks typically prompt targeted **water sample testing** and clinical surveillance due to their rapid onset and severity. *Cholera carriers in the community* - Similar to active cases, while possible to detect **Vibrio cholerae**, sewer swabs are not the primary tool specifically for identifying **cholera carriers**. - **Cholera carriers** are less common and their detection is usually part of broader environmental surveillance during or after an outbreak.
Question 1723: What is the most common nosocomial infection?
- A. Pneumonia
- B. UTI (Correct Answer)
- C. Surgical wound infection
- D. Nephritis
Explanation: ***UTI*** - **Urinary tract infections (UTIs)** are the **most frequently reported nosocomial infections**, accounting for about 40% of all healthcare-associated infections. - This high incidence is primarily due to the frequent use of **urinary catheters**, which introduce bacteria into the urinary tract. *Pneumonia* - While **hospital-acquired pneumonia (HAP)** is a significant and severe nosocomial infection, it is not the most common. - HAP often occurs in critically ill patients, especially those on **mechanical ventilation**. *Surgical wound infection* - **Surgical site infections (SSIs)** are common nosocomial infections but are less frequent than UTIs overall. - They are directly related to surgical procedures and **wound care**. *Nephritis* - Nephritis, an inflammation of the kidneys, is generally considered a **disease process** rather than a common type of nosocomial infection. - While infections can lead to nephritis, nephritis itself is not typically classified as a primary nosocomial infection type.
Question 1724: Which group classification does a state belong to if the prevalence of HIV infection in antenatal women is reported to be less than 1% and in high-risk populations is reported to be less than 5%?
- A. Group A
- B. Group B
- C. Group D
- D. Group C (Correct Answer)
Explanation: ***Group C*** - This classification is used when the **prevalence of HIV infection** in **antenatal women** is **less than 1%** and in **high-risk populations** is **less than 5%**. - These criteria indicate a relatively **low-level epidemic** or a concentrated epidemic among specific risk groups. *Group A* - This group typically refers to states or regions where the **HIV epidemic is generalized**, meaning prevalence is high in the general adult population (>1%). - The criteria for Group A are much higher than described in the question, suggesting widespread transmission beyond specific risk groups. *Group B* - Group B usually describes a situation where the **HIV epidemic is concentrated** in specific **high-risk groups**, but still at a higher prevalence than Group C (e.g., >5% in high-risk populations). - The antenatal prevalence might still be relatively low, but the prevalence in specific at-risk groups would exceed 5%. *Group D* - This classification is not a standard category in the common epidemiological grouping of HIV epidemics. - The established classifications generally include categories like low-level, concentrated, and generalized epidemics, which correspond to the other options.
Question 1725: Under which condition is screening IMPOSSIBLE (most fundamental criterion)?
- A. Prevalence of disease is low
- B. Life expectancy cannot be prolonged by early diagnosis
- C. Diagnostic test is not available
- D. Diseases with no latent period (Correct Answer)
Explanation: ***Diseases with no latent period*** - This is the **MOST FUNDAMENTAL criterion** for screening - without a latent (presymptomatic) period, screening is **IMPOSSIBLE**, not just inefficient. - Screening is designed to detect diseases in their **presymptomatic phase** to allow for early intervention. - If symptoms appear immediately upon disease onset, there is **no detectable pre-clinical phase** to screen for. - This is a **Wilson-Jungner criterion** - the condition must have a recognizable latent or early symptomatic stage. *Prevalence of disease is low* - Low prevalence makes screening **inefficient and not cost-effective** due to low positive predictive value. - However, screening is still **theoretically possible**, just not recommended from a public health perspective. - This is an economic/efficiency criterion, not a fundamental feasibility criterion. *Life expectancy cannot be prolonged by early diagnosis* - If early treatment doesn't improve outcomes, screening lacks **benefit** but is still technically possible. - This relates to the **effectiveness of available treatment**, not the feasibility of screening itself. - Screening without treatment benefit violates the criterion that "there should be an accepted treatment for patients with recognized disease." *Diagnostic test is not available* - Without a suitable test, screening **cannot be performed**, but this is a **resource issue**, not a disease characteristic. - Once a test is developed, screening becomes possible. - The "no latent period" criterion is more fundamental as it relates to the **natural history of the disease** itself.
Question 1726: Cluster testing technique is useful in which of the following conditions?
- A. Viral Meningitis (Correct Answer)
- B. Rubella
- C. Chickenpox
- D. Sexually Transmitted Infections
Explanation: ***Viral Meningitis*** - Cluster testing is particularly useful for **viral meningitis** as it involves testing samples from individuals in a defined cluster or common setting (e.g., school, hostel, military barracks) who develop similar symptoms around the same time - This approach helps to quickly **identify the causative agent** and determine the **extent of an outbreak**, enabling timely public health interventions such as isolation, prophylaxis, and infection control measures - Viral meningitis outbreaks commonly occur in **closed or semi-closed communities**, making cluster-based investigation and testing highly efficient for outbreak control - Examples include **enterovirus** and **mumps virus** outbreaks in institutional settings *Rubella* - While outbreaks can occur, rubella is primarily managed through **routine serological testing** (IgM/IgG antibodies) for individual diagnosis - Focus is on **antenatal screening** for congenital rubella syndrome prevention and monitoring vaccine effectiveness - **Mass vaccination programs** (MMR vaccine) have significantly reduced rubella prevalence, making cluster testing less relevant for routine surveillance *Chickenpox* - Chickenpox (varicella) is typically a **clinical diagnosis** based on the characteristic vesicular rash and does not usually require laboratory confirmation - The **distinctive clinical presentation** makes cluster testing unnecessary in most outbreak situations - Laboratory testing is reserved for **atypical cases**, immunocompromised patients, or when diagnosis is uncertain *Sexually Transmitted Infections* - STIs require **individual-specific testing** for particular pathogens (e.g., gonorrhea, chlamydia, syphilis, HIV) based on individual risk factors and exposure - Management involves **contact tracing** and partner notification rather than cluster-based testing - Transmission is through **direct sexual contact**, not through common source exposure like food or airborne routes, making cluster investigation less applicable
Question 1727: Which method is primarily used to detect cases that may not be identified through other surveillance techniques?
- A. Active surveillance (Correct Answer)
- B. Passive surveillance
- C. Sentinel surveillance
- D. Prevalence rate
Explanation: ***Active surveillance*** - This method involves **proactive efforts by public health officials** to identify cases by directly contacting healthcare providers, visiting facilities, and actively searching for unreported cases. - It is specifically designed to **detect cases that may be missed** by passive reporting systems due to underreporting, lack of awareness, or incomplete reporting. - While resource-intensive, it ensures **comprehensive case detection** and is the gold standard for identifying all cases of diseases under surveillance, particularly during outbreak investigations. *Passive surveillance* - This method relies on **voluntary reporting** by healthcare providers to public health authorities. - It is inexpensive but often **misses cases** due to underreporting, making it the system that active surveillance is designed to supplement. *Sentinel surveillance* - This method uses **carefully selected reporting sites** (hospitals, clinics, or practitioners) to monitor disease trends and provide early warning signals. - It is designed for **monitoring specific diseases** efficiently and detecting emerging patterns, not primarily for finding cases missed by other methods. - Useful for resource-limited settings to track trends without comprehensive reporting. *Prevalence rate* - This is a **descriptive epidemiological measure** indicating the proportion of a population with a disease at a given time. - It is not a surveillance method but rather a **statistical measure** used to assess disease burden.
Question 1728: What is the criterion for blindness as defined in India?
- A. Visual acuity less than 3/60
- B. Visual acuity less than 6/60 (Correct Answer)
- C. Visual acuity less than 12/60
- D. Visual acuity less than 18/60
Explanation: ***Visual acuity less than 6/60*** - In India, **blindness** is officially defined as a visual acuity of **less than 6/60** in the better eye with best possible correction, or a visual field constriction to 20 degrees or worse. - This definition is crucial for determining eligibility for **disability benefits** and access to vision rehabilitation services under the Persons with Disabilities Act. - This threshold represents the minimum criterion for legal blindness in India. *Visual acuity less than 3/60* - A visual acuity of less than 3/60 represents **severe blindness (Category 3)**, which is **worse than the minimum threshold** of 6/60. - This level of vision loss **does qualify as legal blindness** in India, representing a more profound degree of visual impairment. - While 6/60 is the defining threshold, 3/60 indicates even more severe vision loss. *Visual acuity less than 12/60* - Visual acuity less than 12/60 but better than 6/60 indicates **low vision** or moderate visual impairment, but it does **not** meet the criteria for legal blindness in India. - This level is categorized as low vision, where individuals may still benefit from magnifiers and other visual aids. - Such individuals retain significant functional vision for many tasks. *Visual acuity less than 18/60* - A visual acuity of less than 18/60 but better than 6/60 is considered **mild to moderate visual impairment** or low vision, but it does not qualify as legal blindness. - Individuals with this vision level typically retain considerable functional vision, although they may experience difficulties with certain tasks requiring fine detail. - This level may qualify for low vision services but not disability certification for blindness.
Question 1729: Case-control study is an example of?
- A. Retrospective study (Correct Answer)
- B. Prospective study
- C. Combined retrospective and prospective study
- D. Study at one point of time
Explanation: ***Retrospective study*** - In a **case-control study**, researchers look back in time to identify past exposures that may have led to a disease or outcome. - They start with an outcome (cases) and then investigate their past exposures, comparing them to a control group free of the outcome. *Prospective study* - A **prospective study** follows participants forward in time to observe the development of an outcome after an exposure. - Examples include cohort studies, where groups are followed over time to see who develops a disease. *Combined retrospective and prospective study* - This option refers to study designs that incorporate elements of both backward and forward-looking data collection. - While some complex study designs can have both components, a pure case-control study is primarily retrospective. *Study at one point of time* - This describes a **cross-sectional study**, which measures exposure and outcome simultaneously at a single point in time. - Case-control studies, by contrast, involve looking back in time to assess past exposures relative to a current outcome.
Question 1730: NFHS-3 was conducted in?
- A. 1992-93
- B. 1998-99
- C. 2005-06 (Correct Answer)
- D. 2009-10
Explanation: ***2005-06*** - The **National Family Health Survey (NFHS-3)** was indeed conducted during the period of **2005-2006**. - This survey provided crucial data on health and family welfare indicators across India. *1992-93* - This period corresponds to the **National Family Health Survey (NFHS-1)**, the first in the series. - It established baseline data for various health and demographic parameters in India. *1998-99* - This time frame marks the conduction of the **National Family Health Survey (NFHS-2)**. - NFHS-2 provided updated information and trends compared to NFHS-1. *2009-10* - While a significant health survey, this period does not correspond to NFHS-3. No NFHS survey was conducted then.
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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