Non-Communicable Diseases — MCQs

Non-Communicable Diseases Indian Medical PG Practice Questions and MCQs

Question 531: Swine flu is most commonly caused by which influenza virus subtype?

A. H1N1 (Correct Answer)
B. H5N1
C. H3N2
D. B virus

Explanation: **Explanation:** The correct answer is **A. H1N1**. Swine flu is a respiratory disease caused by Type A influenza viruses. The **H1N1 strain** (specifically the pdm09 lineage) was responsible for the 2009 global pandemic and has since become a seasonal human influenza virus. It is characterized by "antigenic shift," where genetic reassortment between human, avian, and swine viruses creates a new subtype that humans have little immunity against. **Analysis of Incorrect Options:** * **B. H5N1:** This is the primary subtype responsible for **Avian Influenza (Bird Flu)**. It has a high mortality rate in humans but lacks efficient human-to-human transmission. * **C. H3N2:** This is a subtype of Influenza A that causes **seasonal flu** in humans. While "variant" H3N2v can spread from pigs to humans, H1N1 remains the most common cause of what is clinically termed "Swine Flu." * **D. B virus:** Influenza Type B viruses generally only infect humans and do not cause pandemics. They are responsible for seasonal epidemics alongside Influenza A. **NEET-PG High-Yield Pearls:** * **Drug of Choice:** Oseltamivir (Tamiflu), a neuraminidase inhibitor, is the treatment of choice for Swine Flu. * **Gold Standard Test:** Real-time Reverse Transcriptase PCR (RT-PCR) using a nasopharyngeal swab. * **Category Classification:** In India, Swine Flu cases are categorized into **A** (mild, no Oseltamivir), **B** (high risk/high fever, Oseltamivir required), and **C** (breathlessness/cyanosis, Oseltamivir + Hospitalization). * **Incubation Period:** Typically 1–4 days.

Question 532: The secondary attack rate of measles is more than mumps. What can be concluded?

A. Measles is more dangerous than mumps.
B. Mumps is more dangerous than measles.
C. Measles is more infectious than mumps. (Correct Answer)
D. Measles is more common than mumps.

Explanation: ### Explanation **1. Understanding the Concept: Secondary Attack Rate (SAR)** The **Secondary Attack Rate (SAR)** is a measure of **infectivity** or communicability. It is defined as the number of exposed persons who develop the disease within the incubation period following exposure to a primary case. * **Formula:** (Number of secondary cases / Total number of susceptible contacts) × 100. * Since measles has a higher SAR (approx. 80%–90%) compared to mumps (approx. 30%–40%), it implies that a susceptible person is much more likely to catch measles after exposure than mumps. Therefore, **Measles is more infectious than mumps.** **2. Analysis of Incorrect Options** * **Options A & B (Dangerousness):** "Dangerousness" refers to **virulence** (severity of disease) or **case fatality rate**. SAR only measures how easily a disease spreads, not how severe the clinical outcome or mortality is. * **Option D (Commonness):** The "commonness" of a disease in a community is measured by **Prevalence**. While high infectivity can lead to more cases, prevalence is also influenced by vaccination coverage, duration of illness, and population density. **3. NEET-PG High-Yield Pearls** * **Highest SAR:** Measles and Pertussis have the highest SAR among common childhood infections (approx. 90%). * **Lowest SAR:** Leprosy has one of the lowest SARs (approx. 3–5%). * **Generation Time:** SAR is calculated based on the "incubation period," but the interval between a primary case and a secondary case is technically called the **Serial Interval**. * **Denominator:** Remember that the denominator for SAR excludes those who are already immune (e.g., previously infected or vaccinated).

Question 533: What preservative is added in the DPT vaccine?

A. Zinc phosphate
B. Aluminum phosphate (Correct Answer)
C. Magnesium sulfate
D. Zinc sulfate

Explanation: **Explanation:** The question asks for the preservative/adjuvant used in the DPT (Diphtheria, Pertussis, and Tetanus) vaccine. The correct answer is **Aluminum phosphate** (or Aluminum hydroxide). **1. Why Aluminum Phosphate is Correct:** In vaccinology, Aluminum salts act as **adjuvants**. Their primary role is to enhance the immune response by creating a "depot effect" at the injection site, allowing for the slow release of antigens and stimulating a stronger antibody production. Without an adjuvant, the toxoids in DPT would be cleared too quickly to trigger an effective immune memory. Note: While the question uses the term "preservative," in the context of DPT, Aluminum salts are technically adjuvants, whereas **Thiomersal** is the actual preservative used to prevent bacterial growth. **2. Why Other Options are Incorrect:** * **Zinc phosphate & Zinc sulfate:** Zinc compounds are not used as adjuvants or stabilizers in standard EPI vaccines. Zinc is primarily used as a nutritional supplement (e.g., in diarrhea management). * **Magnesium sulfate:** This is used clinically as an anticonvulsant (e.g., in Eclampsia) or a laxative, but it has no role in vaccine formulation. **3. High-Yield Clinical Pearls for NEET-PG:** * **Storage:** DPT is a **heat-sensitive** vaccine but, more importantly, it is **freeze-sensitive**. It must be stored between +2°C to +8°C. * **The Shake Test:** If a DPT vial is suspected of being frozen, the "Shake Test" is performed. Freezing causes the aluminum adjuvant to precipitate, leading to rapid sedimentation. * **Route:** DPT is always given **Intramuscularly (IM)**. If given subcutaneously, the aluminum adjuvant can cause local irritation, sterile abscesses, or granulomas. * **Preservative vs. Adjuvant:** If the option "Thiomersal" (mercury derivative) is present, it is the correct answer for the *preservative*; Aluminum salts are the *adjuvants*.

Question 534: What is the diluent used for BCG vaccine?

A. Distilled water
B. Normal saline (Correct Answer)
C. Dextrose solution
D. Ringer's lactate

Explanation: **Explanation:** The BCG (Bacillus Calmette-Guérin) vaccine is a live attenuated vaccine supplied in a freeze-dried (lyophilized) form. It requires reconstitution before administration. **1. Why Normal Saline (0.9% NaCl) is the correct diluent:** Normal saline is used because it is **isotonic** with the live bacteria. It maintains the osmotic pressure of the solution, ensuring the viability of the live-attenuated *Mycobacterium bovis* strain. Using an isotonic solution prevents the bacterial cells from swelling or shrinking, thereby preserving the vaccine's potency. **2. Why other options are incorrect:** * **Distilled Water:** It is hypotonic. Using distilled water would cause the live bacteria to absorb water via osmosis, leading to cell lysis (bursting) and inactivation of the vaccine. It also causes significant local irritation and pain upon injection. * **Dextrose Solution:** The sugar content can alter the pH and provide a substrate for contamination; it is not the standard physiological vehicle for this vaccine. * **Ringer’s Lactate:** While isotonic, the additional electrolytes and lactate buffer are unnecessary and could potentially interfere with the specific stability requirements of the BCG strain. **Clinical Pearls for NEET-PG:** * **Reconstitution Rule:** Once reconstituted, the BCG vaccine must be used within **4–6 hours**. Any leftover vaccine must be discarded to prevent secondary contamination (e.g., *Staphylococcus aureus* leading to Toxic Shock Syndrome). * **Storage:** Both the vaccine vial and the diluent should ideally be stored at **+2°C to +8°C** (protected from light). * **Injection Site:** It is administered **Intradermally** (left upper arm) using an **Omega/Tuberculin syringe**. * **Comparison:** Note that **Measles/MR** vaccine uses **Distilled Water** as a diluent, whereas **BCG** specifically requires **Normal Saline**. This is a frequent point of confusion in exams.

Question 535: Why are four drugs used in the treatment of tuberculosis?

A. To decrease the development of drug resistance through mutation (Correct Answer)
B. To decrease the development of drug resistance through conjugation
C. To cure the disease earlier
D. None of the above

Explanation: **Explanation:** The primary rationale for using a multi-drug regimen (Rifampicin, Isoniazid, Pyrazinamide, and Ethambutol) in tuberculosis (TB) is to **prevent the selection of drug-resistant mutants.** **1. Why Option A is Correct:** *Mycobacterium tuberculosis* undergoes spontaneous chromosomal **mutations** at a predictable frequency (e.g., 1 in $10^6$ for Isoniazid). In a large cavitary lesion containing $10^9$ bacilli, several naturally resistant mutants will exist. If only one drug is used, these mutants survive and multiply (monotherapy leads to resistance). However, the probability of a bacillus being simultaneously resistant to two or more drugs through mutation is the product of their individual probabilities (e.g., $10^{-6} \times 10^{-8} = 10^{-14}$), which is statistically negligible. Thus, multiple drugs ensure that mutants resistant to one drug are killed by the others. **2. Why Other Options are Incorrect:** * **Option B:** Conjugation (horizontal gene transfer) is a common mechanism for spreading resistance in Gram-negative bacteria (via plasmids). However, *M. tuberculosis* does not utilize conjugation; its resistance is strictly due to **vertical transmission of chromosomal mutations.** * **Option C:** While a combination of bactericidal and sterilizing drugs (like Pyrazinamide) allows for a 6-month "short-course" compared to older 18-month regimens, the specific reason for using **four** drugs initially is to prevent resistance in the high-bacillary load phase, not necessarily to shorten the duration further. **High-Yield Clinical Pearls for NEET-PG:** * **Bactericidal drugs:** Rifampicin, Isoniazid, Pyrazinamide, Streptomycin. * **Bacteriostatic drug:** Ethambutol. * **Sterilizing effect:** Highest with Rifampicin and Pyrazinamide (prevents relapse). * **Early Bactericidal Activity (EBA):** Highest with Isoniazid (rapidly makes the patient non-infectious). * **DOTS Strategy:** Aimed at ensuring compliance to prevent the "Acquired Drug Resistance" caused by irregular treatment.

Question 536: The carrying capacity of any given population is determined by its?

A. Population growth rate
B. Birth rate
C. Death rate
D. Limiting resource (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Limiting resource** **Concept Overview:** In demography and ecology, **Carrying Capacity (K)** is defined as the maximum population size of a species that a specific environment can sustain indefinitely, given the food, habitat, water, and other necessities available. The fundamental factor that dictates this ceiling is the **limiting resource**. According to Liebig’s Law of the Minimum, growth is controlled not by the total amount of resources available, but by the scarcest resource (e.g., food supply, space, or clean water). When a population exceeds its carrying capacity, the ecosystem becomes degraded, leading to a natural decline in population until stability is restored. **Analysis of Incorrect Options:** * **A. Population growth rate:** This describes the speed at which a population increases (Births - Deaths). While it determines how *quickly* a population approaches the carrying capacity, it does not determine the capacity itself. * **B & C. Birth rate and Death rate:** These are vital statistics that influence the net growth of a population. While they fluctuate based on environmental stress (e.g., deaths increase when resources are scarce), they are *consequences* of reaching the carrying capacity rather than the *determinants* of it. **High-Yield Clinical Pearls for NEET-PG:** * **Logistic Growth Curve (S-shaped/Sigmoid):** This curve represents a population reaching its carrying capacity. It consists of a lag phase, a log (exponential) phase, and a stationary phase (where N = K). * **Malthusian Theory:** Thomas Malthus suggested that while population grows geometrically (1, 2, 4, 8), food production grows arithmetically (1, 2, 3, 4), leading to a "Malthusian catastrophe" when the carrying capacity is breached. * **Demographic Trap:** A situation where a developing country's population growth exceeds its economic carrying capacity, preventing the transition to lower fertility rates.

Question 537: What is the definition of sputum-positive tuberculosis?

A. One out of two sputum samples is positive. (Correct Answer)
B. Two out of three sputum samples are positive.
C. BACTEC positive.
D. None of the above.

Explanation: **Explanation:** Under the current **National Tuberculosis Elimination Program (NTEP)** guidelines (formerly RNTCP), the definition of a microbiologically confirmed case of pulmonary tuberculosis has evolved to prioritize early detection and treatment initiation. **1. Why Option A is Correct:** According to the current diagnostic algorithm, a patient is classified as **Sputum Positive** if even **one** out of two sputum samples (typically one spot and one morning sample) is positive for Acid-Fast Bacilli (AFB) via Ziehl-Neelsen (ZN) staining or fluorescence microscopy. This "one-positive" criteria was adopted to increase the sensitivity of the screening process and ensure that infectious cases are not missed. **2. Why Other Options are Incorrect:** * **Option B:** The "two out of three" criteria is an outdated protocol. Requiring multiple positive smears significantly increased patient dropout rates during the diagnostic phase. * **Option C:** While BACTEC (a rapid liquid culture system) is a highly sensitive method for detecting *M. tuberculosis*, the standard clinical definition of "sputum-positive TB" specifically refers to smear microscopy findings rather than culture results. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnostic Shift:** The NTEP now prioritizes **NAAT (CBNAAT/TrueNat)** as the initial diagnostic test for TB, which detects both the organism and Rifampicin resistance. * **Sputum Grading:** A minimum of **5,000–10,000 bacilli/ml** of sputum is required for a smear to be positive under ZN staining. * **Screening:** For TB screening in the community, the most sensitive symptom is a cough of **≥ 2 weeks** duration. * **Microscopy:** Fluorescence microscopy is approximately 10% more sensitive than traditional ZN staining and allows for faster examination of slides.

Question 538: What is the recommended dose of chloroquine for children aged 4-8 years?

A. 150 mg
B. 300 mg (Correct Answer)
C. 450 mg
D. 600 mg

Explanation: **Explanation:** The treatment of Malaria in the National Vector Borne Disease Control Programme (NVBDCP) follows age-specific dosage schedules for Chloroquine (CQ). Chloroquine is administered at a total dose of **25 mg/kg** body weight divided over three days (10 mg/kg on Day 1, 10 mg/kg on Day 2, and 5 mg/kg on Day 3). For standardized field use, the dosage is categorized by age groups: * **<1 year:** 75 mg (1/2 tablet) * **1–4 years:** 150 mg (1 tablet) * **4–8 years:** **300 mg (2 tablets)** — **Correct Answer** * **8–12 years:** 450 mg (3 tablets) * **12–15 years:** 600 mg (4 tablets) * **>15 years:** 600 mg (Day 1 & 2) and 300 mg (Day 3) **Analysis of Options:** * **Option A (150 mg):** This is the dose for children aged 1–4 years. * **Option C (450 mg):** This is the dose for children aged 8–12 years. * **Option D (600 mg):** This is the standard adult dose (for Day 1 and Day 2). **High-Yield Clinical Pearls for NEET-PG:** 1. **Standard Tablet:** One tablet of Chloroquine phosphate contains **150 mg base** (250 mg salt). 2. **Mechanism:** It inhibits heme polymerase, leading to the accumulation of toxic heme in the parasite. 3. **Contraindication:** Chloroquine is avoided in patients with psoriasis and retinal diseases. 4. **Pregnancy:** Chloroquine is safe and remains the drug of choice for *P. vivax* in pregnancy. 5. **Radical Cure:** For *P. vivax*, Chloroquine is followed by Primaquine (0.25 mg/kg) for 14 days to prevent relapse (except in G6PD deficiency and pregnancy).

Question 539: Which of the following rodents is the natural reservoir of plague?

A. Mus musculus
B. Tatera indica (Correct Answer)
C. Rattus Rattus
D. Rattus norvegicus

Explanation: ### Explanation **Correct Answer: B. Tatera indica** In the epidemiology of plague (*Yersinia pestis*), it is crucial to distinguish between the **natural (sylvatic) reservoir** and the **commensal (urban) hosts**. 1. **Why Tatera indica is correct:** * *Tatera indica* (the Indian Gerbil) is the **natural reservoir** of plague in India. * Natural reservoirs are wild rodents that are relatively resistant to the disease. They maintain the infection in a "silent" state in nature (enzootic foci) for long periods without dying out, ensuring the long-term survival of the bacteria. 2. **Why the other options are incorrect:** * **C. Rattus rattus (Roof Rat):** This is a commensal peridomestic rodent. It is highly susceptible to plague and usually dies during an outbreak. It acts as the **bridge** that brings the infection from the wild to human dwellings. * **D. Rattus norvegicus (Norway Rat/Sewer Rat):** Similar to *R. rattus*, it is a domestic rodent that acts as a host during urban outbreaks but is not the primary natural reservoir. * **A. Mus musculus (House Mouse):** While it can be infected, it plays a negligible role in the maintenance or transmission of plague compared to *Tatera* or *Rattus* species. ### High-Yield Clinical Pearls for NEET-PG: * **The "Rat Fall":** A sudden increase in the death of commensal rats (*R. rattus*) serves as a warning sign of an impending human plague epidemic. * **Vector:** The most efficient vector for transmitting plague from rat to man is the **Xenopsylla cheopis** (Oriental rat flea). * **Flea Index:** An "Anterior Flea Index" (specifically the *X. cheopis* index) of **>1** is considered a critical threshold for an increased risk of a plague outbreak. * **Drug of Choice:** Streptomycin is the traditional drug of choice; however, Gentamicin or Doxycycline are also frequently used.

Question 540: Which of the following is considered an obesity index?

A. Broca's index (Correct Answer)
B. Ponderal index
C. Quetelet index
D. Corpulence index

Explanation: **Explanation:** Obesity is measured using various anthropometric indices that relate weight to height. While several indices exist, **Broca’s Index** is a classic, simplified method historically used to estimate ideal body weight and identify obesity. * **Why Broca’s Index is the Correct Answer:** Broca’s Index is calculated as: **Height (in cm) – 100 = Ideal Weight (in kg)**. For example, if a person is 170 cm tall, their ideal weight should be 70 kg. Any weight significantly exceeding this calculated value indicates obesity. Its simplicity makes it a frequent topic in community medicine exams. * **Analysis of Other Options:** * **Quetelet Index (Option C):** This is the technical name for **Body Mass Index (BMI)**, calculated as $Weight (kg) / Height (m^2)$. While it is the gold standard for classifying obesity, in the context of this specific question (often derived from standard textbooks like Park’s PSM), Broca’s index is frequently highlighted as a primary "obesity index" alongside BMI. * **Ponderal Index (Option B):** Also known as the Rohrer's Index, it is calculated as $Weight (kg) / Height (m^3)$. It is primarily used in pediatrics to assess fetal growth restriction or neonates, rather than general adult obesity. * **Corpulence Index (Option D):** This is a synonym for the Ponderal Index. **High-Yield Clinical Pearls for NEET-PG:** * **BMI Classifications (WHO):** Underweight (<18.5), Normal (18.5–24.9), Overweight (25–29.9), Obese (≥30). * **Waist-Hip Ratio (WHR):** A measure of central obesity. Obesity is defined as WHR **>0.9 in men** and **>0.85 in women**. * **Waist Circumference:** The best indicator of visceral fat. Action levels: **>102 cm (M)** and **>88 cm (F)** indicate high risk. * **Lorentz’s Formula:** A more refined version of Broca’s index that accounts for gender.

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