Epidemiology Practice Questions

Q: Ability of a screening test to diagnose true positives refers to:

Sensitivity. ### Explanation **Correct Option: B. Sensitivity** Sensitivity is the ability of a screening test to correctly identify those who **actually have the disease** (True Positives). Mathematically, it is the proportion of people with the disease who test positive: * **Formula:** [True Positives (TP) / (True Positives + False Negatives (FN))] × 100. A highly sensitive test is essential for screening because it ensures that very few cases are missed (low false-negative rate). **Why Incorrect Options are Wrong:** * **C. Specificity:** This refers to the ability of a test to correctly identify those **without the disease** (True Negatives). It is the proportion of healthy individuals who test negative. * **A. Relative Risk (RR):** This is a measure of **association** used in cohort studies. It compares the incidence of disease in an exposed group to the incidence in an unexposed group. * **D. Attributable Risk (AR):** This indicates the amount of disease incidence that can be attributed to a specific exposure. it is calculated as [Incidence in exposed – Incidence in unexposed]. **High-Yield Clinical Pearls for NEET-PG:** * **SNOUT:** A highly **S**ensitive test, when **N**egative, rules **OUT** the disease (useful for screening). * **SPIN:** A highly **S**pecific test, when **P**ositive, rules **IN** the disease (useful for confirmation). * **Screening vs. Diagnostic:** Screening tests prioritize **Sensitivity** (to catch all cases), while diagnostic tests prioritize **Specificity** (to confirm the diagnosis). * **Predictive Values:** Unlike sensitivity/specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) are highly dependent on the **prevalence** of the disease in the population.

Q: At what point is the zero dose of the polio vaccine administered?

At birth. **Explanation:** The **Zero Dose** of Oral Polio Vaccine (OPV) refers to the dose administered **at birth** (or as soon as possible within the first 15 days). The primary objective of this dose is to induce local mucosal immunity in the gut before the infant can be exposed to enteric pathogens. It also helps overcome the interference of maternal antibodies that might affect later doses. **Analysis of Options:** * **Option B (Correct):** Under the Universal Immunization Programme (UIP), OPV-0 is given at birth. It is called "zero" because it does not count toward the primary three-dose series (given at 6, 10, and 14 weeks). * **Option A:** DPT (now part of the Pentavalent vaccine) is started at 6 weeks. Waiting until this point would miss the window for early mucosal priming. * **Option C:** Diarrhea is not a contraindication for OPV. In fact, if a child has diarrhea during a routine dose, that dose is administered but not counted; an extra dose is given after recovery. However, this does not define the "zero dose." * **Option D:** If a child already has polio (paralysis), the vaccine will not cure the condition, though they should still be immunized to prevent infection from other strains (Type 1 or 3). **High-Yield NEET-PG Pearls:** * **Type of Vaccine:** OPV (Sabin) is a Live Attenuated vaccine; IPV (Salk) is Killed. * **Storage:** OPV is the most heat-sensitive vaccine; stored at **-20°C**. * **VVM (Vaccine Vial Monitor):** Used to monitor heat exposure. The vaccine is usable as long as the inner square is lighter than the outer circle. * **Current Schedule:** India currently uses **bOPV** (Types 1 & 3) and has introduced **Fractional IPV (fIPV)** at 6 and 14 weeks (intradermal).

Q: True regarding case-control study are all of the following except?

Attributable risk can be known. **Explanation:** In epidemiology, the choice of study design dictates which measures of association can be calculated. The correct answer is **D** because **Attributable Risk (AR)** and **Relative Risk (RR)** cannot be directly calculated from a case-control study; they require **Incidence** data, which is only provided by Cohort studies. **1. Why Option D is the correct answer (The "Except"):** Case-control studies are retrospective; they start with the outcome (disease) and look backward for exposure. Since we do not follow a population over time to see how many new cases develop, we cannot calculate the *Incidence*. Attributable Risk (Incidence in exposed - Incidence in non-exposed) and Relative Risk both require incidence rates as their denominator. **2. Analysis of Incorrect Options:** * **A. Possibility of bias:** True. Case-control studies are highly prone to **Recall Bias** (cases remember exposures better than controls) and **Selection Bias**. * **B. Odds Ratio (OR) can be derived:** True. The Odds Ratio is the characteristic measure of association for case-control studies. It serves as an estimate of Relative Risk when the disease is rare. * **C. Relatively inexpensive:** True. Because they do not require long-term follow-up and usually involve smaller sample sizes, they are faster and cheaper than cohort studies. **High-Yield NEET-PG Pearls:** * **Case-Control Study:** Best for **rare diseases** or diseases with long latency periods. * **Cohort Study:** Best for **rare exposures**; allows calculation of Incidence, RR, and AR. * **Formula for OR:** $(a/c) / (b/d)$ or $ad/bc$. * **Nesting:** A "Nested Case-Control" study is a case-control study conducted within a cohort study, reducing selection and information bias.

Q: Increased motivation by a teacher has been found to increase the marks of students in examinations. This bias is called:

Pygmalion bias. ### Explanation The correct answer is **Pygmalion bias** (also known as the **Rosenthal effect**). **1. Why Pygmalion Bias is Correct:** Pygmalion bias occurs when a researcher’s or teacher’s high expectations of a subject lead to improved performance in that subject. In this scenario, the teacher’s increased motivation and belief in the students act as a self-fulfilling prophecy, subconsciously influencing the students to perform better. In clinical research, this is a type of **investigator bias** where the doctor’s expectations can inadvertently influence the patient’s outcome or the recording of data. **2. Analysis of Incorrect Options:** * **Berksonian Bias (Admission Rate Bias):** This is a type of selection bias that occurs when the sample is taken from a hospital population rather than the general community. It arises because hospitalized individuals have different exposure/disease patterns than the general public. * **Hawthorne Bias:** This occurs when study participants change their behavior simply because they **know they are being observed**, rather than due to any specific intervention or expectation. * **Motivational Bias:** While it sounds plausible, this is not a standard epidemiological term for this phenomenon. It generally refers to errors in judgment caused by the desire to achieve a certain outcome. **3. Clinical Pearls for NEET-PG:** * **Self-fulfilling Prophecy:** Pygmalion effect (Positive expectations → Positive results). * **Golem Effect:** The opposite of Pygmalion; low expectations lead to a decrease in performance. * **Prevention:** The best way to eliminate Pygmalion/Investigator bias in clinical trials is through **Double Blinding**, where neither the investigator nor the participant knows who is receiving the intervention. * **Recall Bias:** Common in Case-Control studies; patients with the disease remember past exposures more clearly than healthy controls.

Q: What are the features of the Revised National Tuberculosis Control Programme (RNTCP)/DOTS Expansion?

Included in National Rural Health Mission (NRHM) in 2005.. The Revised National Tuberculosis Control Programme (RNTCP) is a cornerstone of public health in India. Understanding its structural integration and operational guidelines is crucial for NEET-PG. ### **Explanation of the Correct Answer** **Option B** is correct because RNTCP was formally integrated into the **National Rural Health Mission (NRHM)** in **2005**. This integration was a strategic move to decentralize TB services, improve health system synergy, and utilize the NRHM’s vast infrastructure (like ASHAs) to enhance reach and sustainability. ### **Analysis of Incorrect Options** * **Option A:** RNTCP/NTEP primarily relies on **Passive Case Finding** (patients reporting to clinics). However, the statement "Active case finding is not done" is technically incorrect in the current context, as **Active Case Finding (ACF)** was introduced in 2017 to target vulnerable populations. * **Option C:** While teachers *can* be DOTS providers, they are not the primary agents. The program prioritizes health workers, ASHAs, or community volunteers who are accessible to the patient. * **Option D:** Under RNTCP guidelines, **Designated Microscopy Centers (DMCs)** are established for every **1 lakh (100,000) population** in general areas, and every **50,000 population** in hilly, tribal, or difficult terrains. ### **High-Yield Clinical Pearls for NEET-PG** * **Evolution:** RNTCP was launched in 1993 and renamed the **National Tuberculosis Elimination Program (NTEP)** in 2020. * **Goal:** India aims to eliminate TB by **2025**, five years ahead of the global SDG target (2030). * **Diagnostic Algorithm:** The current protocol emphasizes **CBNAAT/NAAT** as the initial diagnostic test for all presumptive TB cases, moving away from sputum microscopy as the sole primary tool. * **Nikshay Poshan Yojana:** Provides ₹500/month nutritional support to all TB patients.

Q: What best describes demographic transition?

A state where the birth rate and death rate are both low and similar.. **Explanation** **Demographic Transition** refers to the historical shift of a population from high birth and death rates to low birth and death rates as a country develops from a pre-industrial to an industrialized economic system. **Why Option A is correct:** The ultimate goal and final stage (Stage 4/5) of demographic transition is a state of **low stationary equilibrium**. In this stage, both birth rates and death rates have declined significantly and are approximately equal. This results in zero or very low population growth, reflecting advanced socio-economic development, effective family planning, and high-quality healthcare. **Why the other options are incorrect:** * **Option B:** A large difference between birth and death rates characterizes the **"Population Explosion"** phase (Stage 2 and early Stage 3). Here, death rates fall rapidly due to medical advances, but birth rates remain high, leading to rapid natural increase. * **Option C:** Imbalance in the sex ratio is a demographic indicator but does not define the transition process itself. * **Option D:** While a "low birth/low death" population eventually leads to an **aging population** (more elderly), the transition itself describes the shift in vital rates (birth/death), not just the age distribution. **High-Yield NEET-PG Pearls:** * **Stage 1 (High Stationary):** High birth rate, high death rate (e.g., India in the 1920s). * **Stage 2 (Early Expanding):** Death rate begins to decline; birth rate remains high. * **Stage 3 (Late Expanding):** Birth rate begins to decline; death rate continues to fall. **India is currently in late Stage 3.** * **Stage 4 (Low Stationary):** Low birth rate, low death rate. * **Stage 5 (Declining):** Birth rate falls below death rate (Negative growth; e.g., Germany, Japan).

Question 1

Potential Support Ratio (PSR) is defined as:

Accepted Answer

Number of persons aged 15-65 per one older person aged >= 65 years

Answer

Number of persons aged 15-65 per children below 15 years

Answer

Number of persons aged 15-65 per one older person aged > 65 and younger person < 15 years

Answer

Number of persons aged 15-65 per one older person aged > 60 and younger person < 15 years

Question 2

Ability of a screening test to diagnose true positives refers to:

Accepted Answer

Sensitivity

Answer

Relative risk

Answer

Specificity

Answer

Attributable risk

Question 3

Which of the following is true about a single exposure, common vector outbreak?

Accepted Answer

Explosive onset

Answer

Secondary waves occur

Answer

Cases occur with varying incubation periods

Answer

Depends on herd immunity

Question 4

At what point is the zero dose of the polio vaccine administered?

Accepted Answer

At birth

Answer

Before giving DPT

Answer

When the child has diarrhea

Answer

When the child has polio

Question 5

True regarding case-control study are all of the following except?

Accepted Answer

Attributable risk can be known

Answer

Possibility of bias

Answer

Odds ratio can be derived

Answer

Relatively inexpensive

Question 6

What method is used for the disinfection of sputum?

Accepted Answer

Autoclaving

Answer

Boiling

Answer

Sunlight

Answer

Burning

Question 7

Increased motivation by a teacher has been found to increase the marks of students in examinations. This bias is called:

Accepted Answer

Pygmalion bias

Answer

Berksonian bias

Answer

Hawthorne bias

Answer

Motivational bias

Question 8

What are the features of the Revised National Tuberculosis Control Programme (RNTCP)/DOTS Expansion?

Accepted Answer

Included in National Rural Health Mission (NRHM) in 2005.

Answer

Active case finding is not done.

Answer

Teachers act as DOTS agents.

Answer

Microscopy centers are established per 1 lac population.

Question 9

Which of the following diseases are under international surveillance?

Accepted Answer

All of the above

Answer

Poliomyelitis

Answer

Rabies

Answer

Malaria

Question 10

What best describes demographic transition?

Accepted Answer

A state where the birth rate and death rate are both low and similar.

Answer

A state where there is a large difference between the crude birth rate and crude death rate.

Answer

A significant imbalance in the sex ratio within the population.

Answer

A population characterized by a high proportion of individuals at the extreme age ranges.

Epidemiology — MCQs

Epidemiology — MCQs

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