Non-Communicable Diseases — MCQs

Non-Communicable Diseases Indian Medical PG Practice Questions and MCQs

Question 31: Which of the following statements regarding tetanus is FALSE?

A. Transmission occurs through contaminated wounds and injuries.
B. It is more common in winter and dry weather. (Correct Answer)
C. The reservoir includes soil and the intestines of humans and animals.
D. There is no herd immunity or lifelong immunity.

Explanation: ### **Explanation** **Why Option B is the Correct (False) Statement:** Tetanus does not have a strict seasonal pattern like respiratory infections; however, in many regions, it is **more common during the summer and rainy seasons**. This is attributed to increased agricultural activity, outdoor work, and higher exposure to soil (the primary reservoir) during these periods. The statement that it is more common in winter and dry weather is epidemiologically incorrect. **Analysis of Other Options:** * **Option A (True):** Tetanus is typically transmitted through the introduction of *Clostridium tetani* spores into the body via contaminated wounds (lacerations, punctures, or even minor abrasions). * **Option C (True):** The reservoir of infection is ubiquitous. *C. tetani* spores are found in **soil** and the **intestinal tracts** of herbivorous animals (horses, cattle) and humans, where they exist as harmless commensals. * **Option D (True):** This is a high-yield concept. Tetanus is the only vaccine-preventable disease that is **infectious but not contagious**. Since it does not spread from person to person, **herd immunity does not exist**. Furthermore, clinical tetanus does not confer lifelong immunity because the lethal dose of tetanospasmin is lower than the dose required to provoke an immune response. ### **NEET-PG High-Yield Pearls** * **Incubation Period:** Usually 3–21 days (Average: 7–10 days). The shorter the incubation period, the worse the prognosis. * **Period of Communicability:** None (Non-communicable). * **First Sign:** Trismus (lockjaw) due to masseter muscle spasm. * **Risus Sardonicus:** Characteristic "grimace" caused by spasms of the facial muscles. * **Opisthotonus:** Backward arching of the back due to extensor muscle spasms. * **Elimination Goal:** Maternal and Neonatal Tetanus (MNT) elimination is defined as <1 case per 1,000 live births in every district. India achieved this in 2015.

Question 32: If the objective of the investigator is to assess the incidence of tuberculosis infection in a community, what is the most appropriate methodology?

A. Identify all individuals with a positive tuberculin test
B. Perform sputum examination of individuals with chest symptoms
C. Identify new converters to tuberculin test (Correct Answer)
D. Screen all children under five years of age with a tuberculin test

Explanation: ### Explanation **Correct Option: C. Identify new converters to tuberculin test** The core of this question lies in the epidemiological definition of **Incidence**. Incidence refers to the number of **new cases** occurring in a defined population during a specific period. In the context of Tuberculosis (TB) epidemiology: * **Tuberculin Skin Test (TST) conversion** signifies a recent infection (the transition from a negative to a positive state). * By identifying "new converters" (individuals who were previously TST negative but have now become TST positive), an investigator can calculate the **Annual Risk of Tuberculosis Infection (ARTI)**. ARTI is the best indicator to assess the transmission dynamics and the impact of TB control measures in a community. **Analysis of Incorrect Options:** * **Option A:** Identifying all individuals with a positive test measures **Prevalence**, not Incidence. It includes both old and new infections, making it impossible to determine the rate of recent transmission. * **Option B:** Sputum examination identifies **active TB disease** (cases). While important for measuring the prevalence of infectious cases, it does not measure the incidence of *infection* (the entry of the bacilli into a host). * **Option C:** Screening only children under five provides a snapshot of recent transmission in a specific age group, but it is a subset of the population. To assess the incidence of infection for the *community*, tracking conversion across the susceptible population is required. **High-Yield Facts for NEET-PG:** * **ARTI (Annual Risk of TB Infection):** It is the percentage of the population that will get newly infected with TB in one year. * **Rule of Thumb:** An ARTI of 1% roughly corresponds to 50–60 new smear-positive cases per 100,000 population. * **Prevalence vs. Incidence:** Remember, Prevalence = Incidence × Duration (P=I×D). For chronic diseases like TB, prevalence is often used for planning services, but incidence is used to track the trend of the epidemic. * **Tuberculin Test (Mantoux):** Read at 48–72 hours; an induration of ≥10mm is generally considered positive in high-prevalence areas.

Question 33: What does a positive tuberculin skin test indicate?

A. The patient has an immunodeficiency.
B. The patient has developed resistance to tuberculin protein.
C. The patient has been infected with Mycobacterium tuberculosis. (Correct Answer)
D. The patient is currently suffering from active tuberculosis disease.

Explanation: **Explanation:** The Tuberculin Skin Test (TST), or Mantoux test, is based on a **Type IV (Delayed-type) Hypersensitivity reaction**. When Purified Protein Derivative (PPD) is injected intradermally, it triggers sensitized T-lymphocytes in individuals previously exposed to *Mycobacterium tuberculosis*. **1. Why Option C is Correct:** A positive result (induration) indicates that the individual’s immune system has recognized the antigen, signifying **latent or past infection** with *M. tuberculosis*. It confirms that the person has been infected but does not differentiate between a dormant state and active disease. **2. Why Other Options are Incorrect:** * **Option A:** Immunodeficiency (e.g., advanced HIV, malnutrition) typically leads to a **false-negative** result (anergy) because the body cannot mount a T-cell response. * **Option B:** There is no clinical concept of "resistance" to the tuberculin protein; a lack of reaction simply means no prior sensitization or anergy. * **Option C vs. D:** This is a crucial distinction. A positive TST **cannot diagnose active clinical disease**. Diagnosis of active TB requires clinical symptoms, radiological findings, and microbiological confirmation (Sputum AFB/CBNAAT). **High-Yield Clinical Pearls for NEET-PG:** * **Reading the Test:** Results are read after **48–72 hours**. Measure the **induration** (palpable raised area), NOT the erythema. * **False Positives:** Can occur due to **BCG vaccination** (usually <10mm) or infection with Non-Tuberculous Mycobacteria (NTM). * **False Negatives (Anergy):** Seen in miliary TB, AIDS, sarcoidosis, recent viral infections (measles), and use of immunosuppressants. * **Cut-off in India:** Generally, an induration of **≥10 mm** is considered positive in the general population.

Question 34: Which of the following is NOT true about measles?

A. Incubation period is 10-14 days
B. Secondary attack rate is 30-40% (Correct Answer)
C. Subcutaneous vaccine is available
D. Vaccine is live attenuated

Explanation: **Explanation:** The correct answer is **B (Secondary attack rate is 30-40%)** because this statement is factually incorrect. Measles is one of the most highly infectious diseases known to mankind. Its **Secondary Attack Rate (SAR)** in susceptible household contacts is **>80% (often cited as 90%)**, not 30-40%. **Analysis of Options:** * **Option A:** The incubation period of Measles is typically **10–14 days** (from exposure to onset of rash), making this a true statement. * **Option C & D:** The Measles vaccine is a **Live Attenuated vaccine** (Edmonston-Zagreb strain is commonly used in India). It is administered via the **Subcutaneous (SC)** route, usually at 9 completed months and 16-24 months. Both statements are true. **High-Yield Clinical Pearls for NEET-PG:** * **Infectivity Period:** From 4 days before to 4 days after the appearance of the rash. * **Koplik’s Spots:** Pathognomonic feature; small white spots on an erythematous base found on the buccal mucosa opposite the lower 2nd molars during the pre-eruptive stage. * **Vitamin A:** Supplementation is mandatory in measles management to prevent complications like blindness and reduce mortality. * **Complications:** The most common complication is **Otitis Media**; the most common cause of death is **Pneumonia**; the most serious delayed complication is **SSPE** (Subacute Sclerosing Panencephalitis). * **Isolation:** Respiratory isolation is required. Unlike chickenpox, the measles rash is not infectious; it is a result of the immune response.

Question 35: What is the recommended distance for vector control around an airport for yellow fever?

A. 400 m (Correct Answer)
B. 200 m
C. 500 m
D. 100 m

Explanation: **Explanation:** The correct answer is **400 meters (Option A)**. This distance is a standard International Health Regulation (IHR) requirement aimed at preventing the transmission of Yellow Fever via its primary vector, the *Aedes aegypti* mosquito. **Why 400 meters?** The "Aedes-free zone" or "Sanitary zone" is established around airports and seaports to ensure that mosquitoes do not board aircraft or ships. The distance of 400 meters is chosen because it exceeds the typical flight range of the *Aedes aegypti* mosquito, which is generally limited to 100–200 meters. By maintaining a 400m buffer zone free of breeding sites, the risk of "imported" or "exported" yellow fever is significantly minimized. **Analysis of Incorrect Options:** * **Option B (200 m):** While this is the average flight range of the mosquito, it does not provide a sufficient safety margin for international quarantine standards. * **Option C (500 m) & Option D (100 m):** These distances are not recognized by the WHO or IHR for specific vector control perimeters regarding yellow fever. 100m is too short to be effective, and 500m is not the standardized regulatory figure. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Aedes aegypti* (Urban yellow fever) and *Haemagogus* (Sylvan/Jungle yellow fever). * **Vaccine:** 17D strain (Live attenuated). It becomes effective **10 days** after administration and provides **lifelong immunity** (as per 2016 WHO amendments). * **Validity of Certificate:** For international travel, the yellow fever vaccination certificate is valid for life, starting 10 days after vaccination. * **Incubation Period:** 3 to 6 days. * **India Status:** India is "Yellow Fever receptive" (vector is present, but the disease is not). Therefore, strict quarantine and vector control at entry points are mandatory.

Question 36: What is the primary reservoir for scrub typhus?

A. Mites
B. Humans
C. Rodents (Correct Answer)
D. Dogs

Explanation: **Explanation:** **Scrub Typhus** is a rickettsial zoonosis caused by *Orientia tsutsugamushi*. Understanding the transmission cycle is crucial for NEET-PG. **1. Why Rodents are the Correct Answer:** In the transmission cycle of scrub typhus, **rodents** (specifically field mice and rats) serve as the **primary reservoir** of the infection in nature. They maintain the bacteria in the environment, providing a persistent source of infection for the vectors. **2. Analysis of Incorrect Options:** * **Mites (Option A):** While mites (specifically the larval stage called **chiggers**) are the **vectors** that transmit the disease to humans, they are not the primary reservoir. However, they can maintain the bacteria through *transovarial transmission* (acting as a secondary reservoir). * **Humans (Option B):** Humans are **accidental, dead-end hosts**. We do not transmit the disease further and are not involved in maintaining the infection cycle in nature. * **Dogs (Option C):** Dogs are not involved in the epidemiological cycle of scrub typhus. **3. High-Yield Clinical Pearls for NEET-PG:** * **Vector:** Larval stage of trombiculid mites (*Leptotrombidium deliense*). * **Pathognomonic Sign:** The **Eschar** (a painless, black crusty sore at the site of the mite bite) is the most important clinical diagnostic clue. * **Habitat:** "Mite islands" (areas of scrub vegetation where the vector and reservoir coexist). * **Drug of Choice:** **Doxycycline** is the gold standard treatment. Azithromycin is an alternative, especially in pregnancy. * **Diagnosis:** The **Weil-Felix test** (OX-K positive) is a classic but non-specific test; IgM ELISA is now the preferred diagnostic method.

Question 37: The formula shown is known as:

A. Chandler index
B. Human development index
C. Life table analysis
D. Pearl index (Correct Answer)

Explanation: ***Pearl index*** - The **Pearl index** formula calculates contraceptive efficacy using (Number of failures × 1200 / Total months of exposure). - It measures the number of **unintended pregnancies** per 100 woman-years of exposure to a contraceptive method. *Chandler index* - Used to measure **air pollution levels**, specifically **particulate matter** concentration in the atmosphere. - Has no relation to **contraceptive efficacy** or pregnancy failure rates. *Human development index* - A composite index measuring **life expectancy**, **education**, and **per capita income** of countries. - Used for **socioeconomic development** assessment, not for contraceptive method evaluation. *Life table analysis* - A statistical method used to analyze **survival data** and **mortality patterns** over time. - Primarily used in **epidemiology** and **actuarial science**, not for measuring contraceptive failure rates.

Question 38: What is the concentration of sodium in mOsm/L in low osmolar ORS?

A. 45
B. 75 (Correct Answer)
C. 90
D. 60

Explanation: **Explanation:** The WHO and UNICEF recommended the shift from standard ORS to **Low Osmolar ORS** (Reduced Osmolarity ORS) to improve clinical outcomes. The primary goal was to reduce the risk of hypernatremia and decrease the need for unscheduled IV fluids by lowering the total osmolarity. **1. Why 75 mOsm/L is correct:** In the Reduced Osmolarity ORS formulation, the concentration of **Sodium is 75 mmol/L (or mOsm/L)** and **Glucose is 75 mmol/L**. This 1:1 molar ratio is critical because it optimizes the sodium-glucose cotransport mechanism in the small intestine, ensuring maximum water absorption while reducing stool output and vomiting compared to the older formula. **2. Analysis of Incorrect Options:** * **Option A (45):** This is too low for standard rehydration in diarrhea, though some specialized maintenance fluids or "ReSoMal" (used in severe acute malnutrition) have lower sodium levels (approx. 45 mmol/L). * **Option C (90):** This was the sodium concentration in the **Old/Standard WHO ORS**. While effective for cholera, it was found to increase the risk of hypernatremia in children with non-cholera diarrhea. * **Option D (60):** This does not correspond to the sodium concentration of any standard WHO-recommended ORS formulation. **High-Yield Clinical Pearls for NEET-PG:** * **Total Osmolarity of Low Osmolar ORS:** 245 mOsm/L (Old ORS was 311 mOsm/L). * **Composition Breakdown:** Sodium (75), Glucose (75), Potassium (20), Chloride (65), and Trisodium Citrate (10). * **Citrate vs. Bicarbonate:** Citrate is used because it increases the shelf life of the ORS packet and helps correct acidosis. * **Zinc Supplementation:** Always remember that Zinc (20mg/day for 14 days; 10mg for infants <6 months) is given alongside ORS to reduce the duration and severity of diarrhea.

Question 39: Which type of mosquito larvae lie horizontal on the water surface, resting parallel to it?

A. Aedes
B. Anopheles (Correct Answer)
C. Culex
D. Mansonides

Explanation: **Explanation:** The correct answer is **Anopheles**. The orientation of mosquito larvae at the water surface is a classic morphological feature used for identification in medical entomology. **1. Why Anopheles is correct:** Anopheles larvae lack a respiratory siphon (a breathing tube). Instead, they breathe through **respiratory spiracles** located directly on the eighth abdominal segment. To facilitate breathing while remaining submerged, they must lie **parallel (horizontal)** to the water surface. They are also characterized by the presence of **palmate hairs** on their abdominal segments, which help them maintain this horizontal buoyancy. **2. Why the other options are incorrect:** * **Culex:** These larvae possess a long, narrow respiratory siphon. They hang at an **angle (oblique)** to the water surface, with only the tip of the siphon touching the air-water interface. * **Aedes:** Similar to Culex, Aedes larvae have a respiratory siphon (though shorter and stumpier) and hang at an **angle** from the surface. * **Mansonides:** These larvae are unique because they do not come to the surface to breathe. Their siphon is modified to pierce the underwater stems or roots of aquatic plants (like *Pistia*) to extract oxygen. **High-Yield Clinical Pearls for NEET-PG:** * **Anopheles:** Vector for Malaria. Eggs have lateral floats; adults sit at a 45-degree angle to the wall. * **Culex:** Vector for Japanese Encephalitis, Bancroftian Filariasis, and West Nile Virus. Known as the "nuisance mosquito." * **Aedes:** Vector for Dengue, Chikungunya, Zika, and Yellow Fever. Known as the "Tiger mosquito" due to white stripes; they are day-biters. * **Mansonides:** Vector for Brugian Filariasis (*Brugia malayi*). Control requires removal of aquatic vegetation (*Pistia*).

Question 40: What is the most common serotype causing meningococcal epidemics?

A. A (Correct Answer)
B. W-135
C. C
D. Y

Explanation: **Explanation:** **Neisseria meningitidis** is classified into serogroups based on its capsular polysaccharide. While several serogroups cause disease, their epidemiological patterns differ significantly. **Why Option A is Correct:** **Serogroup A** is historically and globally the most common cause of **explosive epidemics**, particularly in the "Meningitis Belt" of sub-Saharan Africa. It is characterized by its ability to spread rapidly through populations, causing large-scale outbreaks every 7–14 years. **Analysis of Incorrect Options:** * **Option B (W-135):** This serogroup is associated with sporadic cases and localized outbreaks, notably linked to Hajj pilgrimage travelers. While it can cause clusters, it does not match the epidemic scale of Serogroup A. * **Option C (C):** Serogroup C causes both sporadic cases and localized outbreaks (often in schools or military camps) in developed countries, but it is less common than A in major global epidemics. * **Option D (Y):** This serogroup is more frequently associated with endemic disease and meningococcal pneumonia, particularly in the United States, rather than large-scale epidemics. **High-Yield Clinical Pearls for NEET-PG:** * **Most common serogroup in India:** Historically Serogroup A (though Serogroup W and B are emerging). * **Most common cause of sporadic cases in developed countries:** Serogroup B (Note: Serogroup B is poorly immunogenic because its polysaccharide resembles human neural cell adhesion molecules). * **Drug of Choice for Prophylaxis:** Rifampicin (Ciprofloxacin or Ceftriaxone are alternatives). * **Drug of Choice for Treatment:** Intravenous Penicillin G (Ceftriaxone if resistance is suspected). * **Vaccine:** The conjugate vaccine (MenAfriVac) has significantly reduced the burden of Serogroup A in Africa.

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