Cold Chain System — MCQs
Post-exposure prophylaxis is indicated in?
Which of the following regarding the vaccine vial monitor (VVM) is true? 1. It is used for monitoring heat exposure of the vaccine by healthcare workers in primary healthcare. 2. It shows cumulative exposure of the vaccine to the heat. 3. It can be used to assess the potential efficacy of the vaccine 4. Calculation of the expiry date can be done using VVM. 5. The expiry date of the vaccine can be relaxed if VVM is an acceptable range. 6. If the square and the circle are the same in color, then the vaccine can be safely used.
The efficiency of cold chain system for oral polio vaccine as monitored by Vaccine Vial Monitor (VVM) depends on:
A 10 week old child comes for vaccination, with previous history of inconsolable cry & fever after getting vaccinated at 6 weeks. What should be done next?
Refrigerated blood stored up to 48 hours before transfusion can destroy which of the following ?
Which is correct about the Vaccine Vial monitor shown in the image? (Recent NEET Pattern 2016-17)
Ideal temperature for DPT storage?
A patient with the following feature shown in the image. The patient reports having another 3-year-old sibling at home, who is fully immunized as per the immunization schedule. What is the best measure to prevent diphtheria in the sibling of the child with diphtheria?
A lady, when exposed to cold, experiences extremities turning blue. Which of the following antibodies is associated with this condition?
A new test was developed for detection of COVID-19. What is the sensitivity of the test as per the information provided above?
Cold Chain System Indian Medical PG Practice Questions and MCQs
Question 1: Post-exposure prophylaxis is indicated in?
- A. Rabies
- B. Diphtheria
- C. HBV
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - Post-exposure prophylaxis (PEP) is a critical intervention for various infectious diseases, including **Rabies**, **Diphtheria**, and **HBV**, to prevent disease development after exposure. - The specific PEP regimen varies by disease but generally involves **vaccines**, **immunoglobulins**, or **antiviral medications**. **Rabies PEP:** - Rabies PEP is indicated after potential exposure to a rabid animal and involves a series of **rabies vaccine** doses and, for unvaccinated individuals, **rabies immune globulin (RIG)**. - Rabies is almost always fatal once symptoms appear, making timely PEP crucial. **Diphtheria PEP:** - Diphtheria PEP is recommended for close contacts of individuals with confirmed diphtheria and typically involves administering a **booster dose of diphtheria toxoid vaccine** and sometimes **antibiotics**. - This helps prevent the spread of *Corynebacterium diphtheriae* and disease development in exposed individuals. **HBV PEP:** - HBV PEP is critical after percutaneous or mucosal exposure to **HBV-infected blood** or body fluids. - It usually includes administering **hepatitis B vaccine** and, in some cases, **hepatitis B immune globulin (HBIG)**, depending on the exposed person's vaccination status and the source's HBV status.
Question 2: Which of the following regarding the vaccine vial monitor (VVM) is true? 1. It is used for monitoring heat exposure of the vaccine by healthcare workers in primary healthcare. 2. It shows cumulative exposure of the vaccine to the heat. 3. It can be used to assess the potential efficacy of the vaccine 4. Calculation of the expiry date can be done using VVM. 5. The expiry date of the vaccine can be relaxed if VVM is an acceptable range. 6. If the square and the circle are the same in color, then the vaccine can be safely used.
- A. 1,2,3,4,5
- B. 3,4
- C. 1,2 (Correct Answer)
- D. 5,6
Explanation: ***Correct: Statements 1, 2*** **Statement 1 - TRUE**: The VVM is primarily designed for **healthcare workers** to monitor vaccine heat exposure at all levels, including primary healthcare settings. This is a key WHO tool for cold chain monitoring. **Statement 2 - TRUE**: VVMs provide a **cumulative record** of time and temperature exposure, reflecting the total heat stress a vaccine has experienced throughout its journey from manufacturer to administration. *Statement 3 - FALSE* - While VVMs assess heat exposure that affects vaccine stability, they do **not directly measure vaccine efficacy** or provide quantitative measures of immune response potential. - Heat damage indicated by VVM indirectly suggests reduced potency, but the VVM itself cannot assess efficacy. *Statement 4 - FALSE* - VVMs are **not used to calculate expiry dates**. Manufacturing expiry dates are determined through stability studies under controlled conditions by the manufacturer. *Statement 5 - FALSE* - The **expiry date cannot be relaxed or extended** based on VVM status. The manufacturer's stated expiry date must always be respected regardless of how favorable the VVM reading is. *Statement 6 - FALSE* - This is the **opposite** of how VVM works. If the **inner square is the same color or darker than the outer circle**, the vaccine has been exposed to excessive heat and **should NOT be used**. - The vaccine is safe when the inner square is lighter than the outer circle.
Question 3: The efficiency of cold chain system for oral polio vaccine as monitored by Vaccine Vial Monitor (VVM) depends on:
- A. Viral potency test
- B. Temperature indicator of the system
- C. Change in the colour of vaccine
- D. Change in colour of monitor (Correct Answer)
Explanation: ***Change in colour of monitor*** - The Vaccine Vial Monitor (VVM) is a label on vaccine vials that changes color progressively when exposed to heat, indicating cumulative heat exposure. - A change in the **VVM's color** signifies that the vaccine may have been exposed to temperatures that could reduce its potency and determines its usability. *Viral potency test* - A **viral potency test** directly measures the amount of live virus in a vaccine sample, which is a laboratory-based assessment and not a real-time field indicator of cold chain efficiency. - While it assesses the vaccine's actual effectiveness, it is not what the VVM monitors in the field for cold chain breaks. *Temperature indicator of the system* - A **temperature indicator** on the cold chain system itself monitors the temperature of the storage unit, not the cumulative heat exposure of individual vaccine vials. - While important for overall cold chain management, it doesn't directly indicate the heat exposure specific to a vaccine vial like a VVM does. *Change in the colour of vaccine* - A change in the **color of the vaccine** itself could indicate contamination or degradation due to various factors, not exclusively due to inadequate cold chain management as monitored by VVM. - The VVM is a separate label designed specifically to monitor heat exposure effects on the vaccine.
Question 4: A 10 week old child comes for vaccination, with previous history of inconsolable cry & fever after getting vaccinated at 6 weeks. What should be done next?
- A. Give DT (Correct Answer)
- B. Defer for 1 month
- C. Administer antibiotics
- D. Give DPT vaccination
Explanation: ***Correct Option: Give DT*** - **Inconsolable crying** (typically defined as crying ≥3 hours) following pertussis-containing vaccine is classified as a **precaution** for subsequent doses per IAP, CDC, and WHO guidelines - When a **precaution** exists, the pertussis component should be **withheld** from future doses - **DT vaccine** (diphtheria-tetanus without pertussis) ensures continued protection against diphtheria and tetanus while avoiding repeat exposure to the pertussis antigen that likely caused the reaction - This represents appropriate **risk-benefit assessment** in immunization practice *Incorrect: Give DPT vaccination* - Continuing DPT after inconsolable crying ignores established AEFI (Adverse Events Following Immunization) guidelines - While fever alone is not a contraindication, **inconsolable crying is a recognized precaution** that warrants modification of the vaccination schedule - Repeating the same vaccine risks recurrence of the adverse event *Incorrect: Defer for 1 month* - Simply deferring without changing the vaccine type doesn't address the underlying issue - The child would still receive the pertussis component later, risking another adverse reaction - Unnecessary delay in protection against diphtheria and tetanus when DT is available *Incorrect: Administer antibiotics* - **Post-vaccination fever and crying** are inflammatory responses to vaccine antigens, not bacterial infections - Antibiotics have no role in managing vaccine-related reactions - This approach doesn't address the need for continued immunization protection
Question 5: Refrigerated blood stored up to 48 hours before transfusion can destroy which of the following ?
- A. Hepatitis B
- B. P. Vivax
- C. Treponema pallidum (Correct Answer)
- D. HIV
Explanation: ***Treponema pallidum*** - *Treponema pallidum*, the causative agent of **syphilis**, is highly sensitive to cold temperatures and **does not survive well in refrigerated blood** stored for more than a few days (typically 24-48 hours). - This characteristic makes the risk of **transfusion-transmitted syphilis** extremely low for stored blood components. *Hepatitis B* - **Hepatitis B virus (HBV)** is very hardy and can survive for extended periods, even in refrigerated blood. - Blood donations are routinely screened for HBV to prevent **transfusion-associated hepatitis**. *P. Vivax* - *Plasmodium vivax*, one of the species causing **malaria**, can survive in refrigerated blood, as the parasites can remain viable within red blood cells [1]. - Transmission of malaria through blood transfusion is a known risk, especially in endemic areas, and is not mitigated by refrigeration alone. *HIV* - **Human Immunodeficiency Virus (HIV)** can survive in refrigerated whole blood and blood components for the duration of their typical storage periods. - Therefore, strict screening of blood donors for HIV antibodies and antigens is crucial to prevent **transfusion-related HIV transmission**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 398-400.
Question 6: Which is correct about the Vaccine Vial monitor shown in the image? (Recent NEET Pattern 2016-17)
- A. Vaccine can be used, if expiry date not passed
- B. Vaccine can be used, after expiry date
- C. Vaccine cannot be used, irrespective of expiry date (Correct Answer)
- D. Vaccine is at discard point, consult supervisor
Explanation: ***Vaccine cannot be used, irrespective of expiry date*** - The image shows a **darker inner square** compared to the outer circle, indicating that the vaccine has been exposed to detrimental heat. - A VVM turning dark signifies that the vaccine has lost its **potency** and should not be administered, regardless of the expiry date. *Vaccine can be used, if expiry date not passed* - This statement is incorrect because the VVM clearly indicates **heat exposure** has compromised vaccine quality, making it unsuitable for use. - The VVM overrides the expiry date when it shows significant heat damage, as vaccine potency is reduced even if not expired. *Vaccine can be used, after expiry date* - This is incorrect as a vaccine should never be used **after its expiry date**, irrespective of the VVM status, as sterility and potency cannot be guaranteed. - Using expired vaccines poses a **health risk** and may not provide adequate protection. *Vaccine is at discard point, consult supervisor* - While it is at the discard point, consulting a supervisor is not the primary instruction; the vaccine is simply **unsuitable for use**. - The VVM is designed to be a **clear indicator** for immediate action, not necessarily requiring further consultation for the general health worker.
Question 7: Ideal temperature for DPT storage?
- A. Room temperature
- B. 4 to 8°C (Correct Answer)
- C. 0 to - 20°C
- D. None of the options
Explanation: ***4 to 8°C*** - The ideal temperature for DPT (diphtheria, pertussis, tetanus) vaccine storage is between **+2°C and +8°C** (or 35°F and 46°F), which is the standard refrigerator temperature range. - This temperature range is crucial for maintaining the **potency** and **efficacy** of the vaccine, preventing **degradation** due to excessive heat or cold. *Room temperature* - Storing DPT vaccines at **room temperature** (typically 20-25°C or 68-77°F) for extended periods can lead to a **loss of potency** as heat can degrade vaccine components. - While short-term excursions within this range might be permissible under specific conditions (e.g., during transport), it is not the ideal long-term storage solution. *0 to - 20°C* - DPT vaccines, particularly the **whole-cell pertussis (wP)** component, can be **damaged by freezing**. - Temperatures below 0°C can cause the **adjuvant** (usually aluminum salt) to separate, leading to a loss of efficacy and potential local reactions at the injection site. *None of the options* - This option is incorrect because **4 to 8°C** is indeed the established and recommended ideal storage temperature for DPT vaccines.
Question 8: A patient with the following feature shown in the image. The patient reports having another 3-year-old sibling at home, who is fully immunized as per the immunization schedule. What is the best measure to prevent diphtheria in the sibling of the child with diphtheria?
- A. Give diphtheria toxoid booster
- B. Give a full course of DPT vaccine
- C. Give prophylactic erythromycin (Correct Answer)
- D. Nothing is required to be done
Explanation: ***Correct: Give prophylactic erythromycin*** - Erythromycin is the **recommended antimicrobial prophylaxis** for close contacts of diphtheria patients to eradicate *Corynebacterium diphtheriae* carriage. - This prevents asymptomatic carriers from transmitting the bacteria, even if vaccinated, as vaccination provides immunity against the toxin, not necessarily against carriage. *Incorrect: Give diphtheria toxoid booster* - While immunization reduces the risk of symptomatic diphtheria disease by inducing **antitoxin immunity**, it does not reliably prevent nasal or pharyngeal carriage of the bacteria. - A booster might be considered if the last dose was more than 5 years ago, but it is not the primary immediate measure to prevent transmission from a known contact. *Incorrect: Give a full course of DPT vaccine* - The patient's sibling is already reported to be **fully immunized**, implying they have received the appropriate doses of the DPT vaccine according to the immunization schedule. - Giving a full course when already immunized would be redundant and ineffective to prevent immediate exposure and potential carriage. *Incorrect: Nothing is required to be done* - Close contacts of diphtheria cases are at **high risk of acquiring and transmitting the infection**, even if they are fully immunized, as immunization protects against the toxin but not necessarily carriage. - Failure to intervene would allow potential colonization and transmission, posing a risk to the community and the contact themselves.
Question 9: A lady, when exposed to cold, experiences extremities turning blue. Which of the following antibodies is associated with this condition?
- A. Anti-RO
- B. Anti-SS-B
- C. Anti-SS-A
- D. Anti-SCL-70 (Correct Answer)
Explanation: Anti-SCL-70 - The symptom of extremities turning blue, especially upon cold exposure, describes **Raynaud's phenomenon**, a common feature of **systemic sclerosis (scleroderma)** [1]. - **Anti-SCL-70 antibodies** (topoisomerase 1 antibodies) are highly specific for **diffuse cutaneous systemic sclerosis**, a severe form of the disease often associated with Raynaud's. *Anti-RO* - **Anti-RO (SSA) antibodies** are primarily associated with **Sjögren's syndrome** and **subacute cutaneous lupus erythematosus**, conditions not typically characterized by prominent Raynaud's as the presenting symptom [2]. - While Sjögren's syndrome can have Raynaud's, it's not the defining feature and other symptoms like **dry eyes** and **dry mouth** would likely be present. *Anti-SS-B* - **Anti-SS-B (La) antibodies** are also associated with **Sjögren's syndrome**, often appearing alongside anti-RO antibodies [2]. - Their presence does not directly point to diffuse systemic sclerosis or severe Raynaud's as the primary condition. *Anti-SS-A* - **Anti-SS-A (RO) antibodies** are primarily linked to **Sjögren's syndrome** and **neonatal lupus**, and can also be seen in **systemic lupus erythematosus** [2]. - While Raynaud's can occur in lupus, the presence of isolated cold-induced blue extremities points more strongly towards systemic sclerosis given the provided options.
Question 10: A new test was developed for detection of COVID-19. What is the sensitivity of the test as per the information provided above?
- A. 97%
- B. 37.5% (Correct Answer)
- C. 20.5%
- D. 60%
Explanation: ***37.5%*** - **Sensitivity** is calculated as the number of **true positives** divided by the sum of true positives and false negatives (i.e., total number of individuals with the disease). - From the table, **True Positives (Test Positive and Disease +)** = 60, and **False Negatives (Test Negative and Disease +)** = 100. So, sensitivity = 60 / (60 + 100) = 60 / 160 = 0.375 or 37.5%. *97%* - This value is incorrect. It might be confused with **Negative Predictive Value (NPV)**, which is the probability that subjects with a negative test truly don't have the disease (1800/1900 ≈ 0.947 or 94.7%), but it's not 97%. - It does not correctly represent the calculation for sensitivity as described above. *20.5%* - This value is incorrect. It does not correspond to any standard epidemiological measure of test performance based on the provided data. - This percentage might arise from an incorrect division or addition of values from the table. *60%* - This value is incorrect. While 60 **true positives** are present, sensitivity requires dividing this by the total number of diseased individuals, not just any other total. - This could be confused with the ratio of true positives to total positive tests (Positive Predictive Value), which would be 60/100, resulting in 60%, but this is not sensitivity.
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