NEET-PG 2012 - Community Medicine Practice Questions

Q: All of the following are characteristics of case control study except:

Measures incidence rate. ***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.

Q: Transovarian transmission is seen in which of the following infections?

Yellow fever. ***Yellow fever*** - **Transovarian transmission** refers to the passage of a pathogen from an adult female arthropod (like a mosquito) to her offspring via the eggs. This mechanism allows the virus to persist in the **vector population** even in the absence of infected vertebrate hosts. - **Yellow fever virus** is known to undergo transovarian transmission in its mosquito vectors, particularly *Aedes aegypti* and other *Aedes* species. *Plague* - Plague is caused by the bacterium *Yersinia pestis* and is primarily transmitted by **flea bites** from infected rodents to humans. - It does not involve transovarian transmission; the fleas acquire the bacteria during a **blood meal** from an infected host. *Ebola fever* - Ebola virus is transmitted through **direct contact** with blood or bodily fluids of infected humans or animals. - It is not an **arthropod-borne disease** and therefore does not exhibit transovarian transmission. *None of the options* - This option is incorrect because **Yellow Fever** clearly demonstrates transovarian transmission within its mosquito vector.

Q: Which of the following diseases does not have a chronic carrier state?

Tetanus. ***Tetanus*** - Tetanus is caused by the toxin produced by *Clostridium tetani*, which is an **environmental bacterium** found in soil and does not establish a persistent infection within humans. - Humans are merely **accidental hosts** for this bacterium, meaning there is **no chronic carrier state** where an infected individual continuously harbors and transmits the pathogen. - The disease occurs through wound contamination with spores, not human-to-human transmission. *Measles* - Measles is an **acute viral infection** with no chronic carrier state in the classical sense. - After acute infection, the virus is cleared from the body in immunocompetent individuals. - While **subacute sclerosing panencephalitis (SSPE)** represents a rare persistent infection, this is **not a carrier state** as the virus is not transmissible from these individuals. - SSPE occurs years after initial infection but does not involve viral shedding or transmission. *Malaria* - Individuals infected with ***Plasmodium* parasites** can develop a **chronic carrier state**, particularly with *P. vivax* and *P. ovale*, which form hypnozoites in the liver. - These parasites can remain dormant and then reactivate, causing **relapses** and allowing for continued transmission to mosquitoes over extended periods. - Chronic asymptomatic carriers can serve as reservoirs for transmission in endemic areas. *Poliomyelitis* - Individuals infected with poliovirus can shed the virus in their stools for **several weeks to months** after infection. - In **immunodeficient individuals**, prolonged excretion can occur for years, creating chronic carriers. - This prolonged shedding allows for the **continued transmission** of the virus within a population.

Q: What does a highly sensitive test imply about its false negative rate?

Low false negative rate. ***Low false negative rate*** - A highly **sensitive test** is good at identifying true positives, meaning it correctly identifies most people who have the disease. - Sensitivity = TP/(TP+FN), so high sensitivity mathematically means few false negatives. - This characteristic directly translates to a **low false negative rate**, as few people with the disease will be missed. *High false positive rate* - A high **false positive rate** relates to **specificity**, not sensitivity. - False positive rate = FP/(FP+TN), which measures how many healthy people are incorrectly identified as diseased. - While some sensitive tests may have lower specificity (higher FP rate), this is not a direct implication of high sensitivity. *High true negative rate* - A high **true negative rate** is a characteristic of a highly **specific** test, which correctly identifies people who do **not** have the disease. - True negative rate = TN/(TN+FP) = Specificity. - **Sensitivity** and **specificity** are independent measures, so high sensitivity does not imply a high true negative rate. *High true positive rate* - High **true positive rate** is actually another term for high sensitivity (Sensitivity = TPR = TP/(TP+FN)). - While this is true of a sensitive test, the question specifically asks about the implication for the **false negative rate**. - The **most direct answer** regarding false negatives is "low false negative rate" rather than describing the true positive rate.

Q: What is the Chandler's Index for Hookworm that indicates a significant health problem?

> 50. ***> 50*** - A Chandler's Index of **> 50** indicates a significant public health problem due to **hookworm infection**. - **Chandler's Index** is calculated as the **average egg count per person in a community** (total hookworm eggs counted ÷ number of persons examined), used to assess the population-level burden of hookworm infection. - A value **> 50** suggests that the community has a significant hookworm problem requiring public health intervention. *> 300* - This value is significantly higher than the threshold for a significant public health problem and would indicate an **extremely severe burden of infection**. - While this represents a very high Chandler's Index, it's not the standard cut-off for defining a "significant" health problem (which is the lower threshold of >50). *> 200* - A Chandler's Index of **> 200** would denote a very high intensity of hookworm infection in the community. - However, this is not the standard threshold used to define when hookworm becomes a "significant" public health issue - the threshold is lower at >50. *> 100* - A Chandler's Index of **> 100** represents a substantial level of hookworm infection within a population. - However, the widely recognized cutoff for a "significant health problem" is **> 50**, indicating public health concern even at this moderate level of community infection burden.

Q: What is the key characteristic of Body Mass Index (BMI) considerations for the Asian population?

Increased morbidity at lower values. ***Increased morbidity at lower values*** - Due to differences in body composition and fat distribution, Asian populations tend to experience **higher risks of developing obesity-related diseases** (e.g., type 2 diabetes, cardiovascular disease) at **lower BMI values** compared to non-Asian populations. - This increased morbidity at lower BMI values highlights the need for population-specific BMI cut-offs for health risk assessment. *BMI cut-offs for obesity differ from international standards* - While it is true that **BMI cut-offs for obesity differ for Asian populations**, this option does not fully describe *why* these cut-offs differ. - The difference in cut-offs is precisely *because* increased morbidity is seen at lower BMI values, making this option less specific than the correct answer. *Increased morbidity at higher BMI values* - While morbidity does increase at higher BMI values in all populations, this statement is **true for Caucasians and other populations**, but the defining characteristic for Asian populations is the *lower* BMI at which morbidity risk begins to significantly increase. - This option does not capture the unique aspect of BMI and health risks in the Asian population. *Obesity is defined as > 25 kg/m2* - For many Asian populations, a BMI of **> 25 kg/m²** is often used as the cut-off for **overweight**, not necessarily obesity, and **obesity is often defined at > 27.5 kg/m² or 30 kg/m² depending on the specific group**. - The international standard for obesity (BMI ≥ 30 kg/m²) is often considered too high for many Asian populations to capture risk effectively.

Q: What is the role of iodized salt in the iodine deficiency control programme?

Primary prevention of iodine deficiency. ***Primary prevention of iodine deficiency*** - **Iodized salt** is a population-wide strategy to ensure adequate **iodine intake** in communities, preventing deficiency before it even occurs. - It aims to maintain normal **thyroid hormone** production and prevent disorders like **goiter** and **cretinism** in healthy individuals. *Secondary prevention of iodine deficiency* - **Secondary prevention** focuses on early diagnosis and prompt treatment in individuals already showing signs of a disease to prevent progression. - While screening for **iodine deficiency disorders (IDD)** might be secondary prevention, the universal use of iodized salt is not targeted at already deficient individuals but at the entire population. *Tertiary prevention of iodine deficiency* - **Tertiary prevention** involves managing existing conditions to prevent complications, reduce disability, and improve quality of life after a disease has manifested. - This would involve treating conditions like **severe hypothyroidism** or **cretinism** that result from prolonged iodine deficiency, for which **iodized salt** is not a direct treatment but a preventative measure. *Not applicable* - This option is incorrect as **iodized salt** plays a crucial and well-established role in public health for controlling **iodine deficiency**. - The scientific evidence and public health initiatives globally highlight its significant applicability in preventing **iodine deficiency disorders**.

Q: Which of the following is not classified as a special incidence rate?

Standardized mortality rate. ***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.

Q: Which of the following is not typically screened for in blood donations?

Epstein-Barr Virus (EBV). ***Epstein-Barr Virus (EBV)*** ✓ - EBV is **NOT routinely screened** for in blood donations in India and most countries - While EBV is a common virus (>90% adults are seropositive), it is **not considered a major transfusion-transmitted infection** - The virus is primarily transmitted through saliva; transfusion-associated EBV transmission is **extremely rare and usually not clinically significant** in immunocompetent recipients - Risk-benefit analysis does not support routine screening due to **high prevalence, low clinical impact, and cost considerations** - EBV screening may only be considered for specific recipients (e.g., severely immunocompromised patients) *HIV* - **Routinely screened** in all blood donations worldwide - Screening includes HIV-1 and HIV-2 antibodies and/or HIV antigen/RNA testing - Transfusion-transmitted HIV causes AIDS with severe consequences - Mandatory screening under the Drugs and Cosmetics Act in India *HBV* - **Routinely screened** in all blood donations - Screening includes HBsAg (Hepatitis B surface antigen) testing, and often anti-HBc or HBV DNA - Can cause acute and chronic hepatitis, cirrhosis, and hepatocellular carcinoma - Mandatory screening in India and globally *HCV* - **Routinely screened** in all blood donations - Screening includes anti-HCV antibodies and/or HCV RNA (nucleic acid testing) - Major cause of chronic hepatitis, cirrhosis, and liver cancer - Mandatory screening under blood safety regulations

Q: What is the osmolarity of the new Oral Rehydration Solution (ORS)?

245. ***245*** - The **new ORS (reduced osmolarity ORS)** has an osmolarity of **245 mOsmol/L**. - This reduced osmolarity formulation has been shown to be more effective in reducing stool output, vomiting, and duration of diarrhea compared to the standard ORS. *270* - While 270 mOsmol/L is closer to the target, it is not the exact osmolarity of the **new ORS formulation**. - The precise osmolarity of the new ORS is specifically designed for optimal water and electrolyte absorption. *290* - The **standard (or traditional) ORS** had an osmolarity of **310 mOsmol/L**, which is higher than 290 mOsmol/L. - An osmolarity of 290 mOsmol/L does not correspond to a recognized standard or new ORS formulation. *310* - The **standard (or traditional) ORS** formulation had an osmolarity of **310 mOsmol/L**. - The move to a new ORS with reduced osmolarity was to improve efficacy and reduce the risk of hypernatremia in some patients.

Question 1

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

Accepted Answer

Measures incidence rate

Answer

Quick results are obtained

Answer

Inexpensive study

Answer

Proceeds from effect to cause

Question 2

Transovarian transmission is seen in which of the following infections?

Accepted Answer

Yellow fever

Answer

Plague

Answer

Ebola fever

Answer

None of the options

Question 3

Which of the following diseases does not have a chronic carrier state?

Accepted Answer

Tetanus

Answer

Malaria

Answer

Measles

Answer

Poliomyelitis

Question 4

What does a highly sensitive test imply about its false negative rate?

Accepted Answer

Low false negative rate

Answer

High false positive rate

Answer

High true negative rate

Answer

High true positive rate

Question 5

What is the Chandler's Index for Hookworm that indicates a significant health problem?

Accepted Answer

> 50

Answer

> 200

Answer

> 100

Answer

> 300

Question 6

What is the key characteristic of Body Mass Index (BMI) considerations for the Asian population?

Accepted Answer

Increased morbidity at lower values

Answer

BMI cut-offs for obesity differ from international standards

Answer

Increased morbidity at higher BMI values

Answer

Obesity is defined as > 25 kg/m2

Question 7

What is the role of iodized salt in the iodine deficiency control programme?

Accepted Answer

Primary prevention of iodine deficiency

Answer

Secondary prevention of iodine deficiency

Answer

Tertiary prevention of iodine deficiency

Answer

Not applicable

Question 8

Which of the following is not classified as a special incidence rate?

Accepted Answer

Standardized mortality rate

Answer

Attack rate

Answer

Secondary attack rate

Answer

Hospital admission rate

Question 9

Which of the following is not typically screened for in blood donations?

Accepted Answer

Epstein-Barr Virus (EBV)

Answer

HIV

Answer

HBV

Answer

HCV

Question 10

What is the osmolarity of the new Oral Rehydration Solution (ORS)?

Accepted Answer

245

Answer

270

Answer

290

Answer

310

NEET-PG 2012 — Community Medicine