Blood Groups and Transfusion — MCQs

10 questions

Although more than 400 blood groups have been identified, the ABO blood group system remains the most important in clinical medicine because it is essential for safe blood transfusions. Which of the following statements about the ABO blood group system is correct?

Direct Coombs test is positive in all EXCEPT:

Which of the following statements is true regarding the Duffy Fy(a-b-) blood group?

A CKD patient had to undergo dialysis. His Hb was 5.5. So two blood transfusions were to be given. First bag was completed in 2 hours. Second was started and midway between he developed shortness of breath, hypertension. Vitals: BP 180/120 mm Hg and pulse rate 110/min. What is the cause?

Anti-D prophylaxis is required in which of the following situations?

Case of trauma in a patient with an unknown blood group. Patient is unstable and requires urgent blood transfusion. Which type of blood should be transfused?

Which of the following components are involved in non-IgE mediated anaphylactic reactions?

Blood transfusion associated acute lung injury occurs due to -

What is the primary stimulus for erythropoietin production?

Q10

What is the primary function of Langerhans' cells?

Blood Groups and Transfusion Indian Medical PG Practice Questions and MCQs

Question 1: Although more than 400 blood groups have been identified, the ABO blood group system remains the most important in clinical medicine because it is essential for safe blood transfusions. Which of the following statements about the ABO blood group system is correct?

A. The ABO blood group system divides blood into four groups: A, B, AB, and O.
B. In the ABO blood group system, antibodies are present in plasma when the corresponding antigen is absent on red blood cells. (Correct Answer)
C. The ABO blood group system was the first blood group system to be discovered in 1901.
D. ABO antigens are found in most body tissues and fluids.

Explanation: ***In the ABO blood group system, antibodies are present in plasma when the corresponding antigen is absent on red blood cells [3], [5].*** - This statement is correct and is a fundamental principle of the ABO system, explaining why individuals with type A blood have **anti-B antibodies** and vice versa, preventing incompatible transfusions [2], [5]. - The presence of naturally occurring antibodies against the missing ABO antigens ensures immediate and potent transfusion reactions if incompatible blood is transfused. *The ABO blood group system divides blood into four groups: A, B, AB, and O [1], [3].* - While the ABO system does classify blood into these four main groups, this statement alone is not the most comprehensive or explanatory characteristic of its clinical importance compared to the antibody-antigen relationship. - The existence of these four groups is a result of the **presence or absence of A and B antigens** on the red blood cell surface [3]. *The ABO blood group system was the first blood group system to be discovered in 1901.* - The ABO blood group system was indeed discovered in **1901 by Karl Landsteiner**, who was later awarded the Nobel Prize for this discovery, making it the **first significant blood group system identified**. - However, while historically important, this statement describes its discovery history rather than a core principle of its biological function or clinical relevance in the same way the antibody rule does [4]. *ABO antigens are found in most body tissues and fluids.* - ABO antigens are found not only on **red blood cells** but also on the surface of most other **body cells**, including epithelial cells, and in secretions like saliva and tears in individuals known as "secretors." - This widespread distribution is crucial for tissue typing in organ transplantation but is not the primary reason for the ABO system's paramount importance in safe blood transfusions compared to the antibody-antigen incompatibility rule.

Question 2: Direct Coombs test is positive in all EXCEPT:

A. G6PD deficiency (Correct Answer)
B. Rh incompatibility
C. Autoimmune hemolysis
D. ABO incompatibility

Explanation: ***G6PD deficiency*** - **G6PD deficiency** is an intrinsic red blood cell defect that leads to hemolytic anemia, but it does **not involve immune-mediated destruction** of red blood cells. - The **Direct Coombs test** detects antibodies or complement components bound to the surface of red blood cells; since G6PD deficiency is not immune-mediated, the test will be negative. *Rh incompatibility* - **Rh incompatibility** occurs when maternal antibodies cross the placenta and target fetal red blood cells, leading to **immune-mediated hemolysis** [1]. - The anti-D antibodies bind to fetal red blood cells, resulting in a **positive Direct Coombs test** (detecting antibody-coated fetal RBCs) [1]. *Autoimmune hemolysis* - **Autoimmune hemolysis** involves the body producing **autoantibodies** against its own red blood cells, leading to their premature destruction [3]. - These autoantibodies (e.g., IgG, IgM) bind to the red blood cell surface, making the **Direct Coombs test positive** [3]. *ABO incompatibility* - **ABO incompatibility** involves the presence of naturally occurring antibodies (e.g., anti-A, anti-B) in a recipient's plasma that react with donor red blood cells [2]. - When incompatible red blood cells are transfused, or in cases of **hemolytic disease of the newborn** due to ABO incompatibility, antibodies bind to the RBCs, resulting in a **positive Direct Coombs test** [2].

Question 3: Which of the following statements is true regarding the Duffy Fy(a-b-) blood group?

A. lacks H- antigen
B. lacks A-antigen
C. All of the options
D. lacks Fy(b) antigen (Correct Answer)

Explanation: ***lacks Fy(b) antigen*** - The **Duffy Fy(a-b-)** phenotype indicates absence of both Fya and Fyb antigens on red blood cells. - Since the phenotype is **Fy(a-b-)**, it definitively lacks the **Fyb antigen** (indicated by the "b-" notation). - This phenotype is common in people of **African descent** and confers natural **resistance to Plasmodium vivax malaria**, as these antigens serve as receptors for the parasite to enter RBCs. *lacks H- antigen* - The **H antigen** belongs to the **H/h blood group system** and is a precursor to A and B antigens in the ABO system. - The absence of H antigen (Bombay phenotype - Oh) is completely **unrelated to the Duffy blood group system**. - Duffy antigens are on the **DARC (Duffy Antigen Receptor for Chemokines)** protein, distinct from the H antigen. *lacks A-antigen* - The **A antigen** is part of the **ABO blood group system** and defines blood types A and AB. - The Duffy blood group system is **genetically and structurally independent** from the ABO system. - Having Fy(a-b-) phenotype does not affect A antigen expression. *All of the options* - This is incorrect because the Duffy Fy(a-b-) phenotype **specifically refers only to the absence of Duffy antigens** (Fya and Fyb). - It has **no relationship** with A, B, or H antigens, which belong to different blood group systems controlled by different genes on different chromosomes.

Question 4: A CKD patient had to undergo dialysis. His Hb was 5.5. So two blood transfusions were to be given. First bag was completed in 2 hours. Second was started and midway between he developed shortness of breath, hypertension. Vitals: BP 180/120 mm Hg and pulse rate 110/min. What is the cause?

A. Allergic
B. FNHTR
C. Transfusion related circulatory overload (TACO) (Correct Answer)
D. TRALI

Explanation: ***Transfusion related circulatory overload (TACO)*** - The patient's presentation with **shortness of breath**, **hypertension**, and **tachycardia** following blood transfusion, especially in a **CKD patient** with likely compromised cardiac and renal function, is highly suggestive of **TACO** [1]. - **Fluid overload** from the transfused blood, exacerbated by pre-existing renal impairment, leads to acute pulmonary edema and cardiovascular stress. *Allergic* - Allergic reactions typically manifest with **urticaria**, **pruritus**, **bronchospasm**, or **anaphylaxis**, often without severe hypertension or primary respiratory distress in this manner [1], [2]. - While mild allergic reactions can occur, the prominent hypertension and acute respiratory distress point away from a simple allergic response. *FNHTR* - **Febrile non-hemolytic transfusion reaction (FNHTR)** is characterized by a temperature increase of at least 1°C, chills, and rigors, usually without significant respiratory distress or marked hypertension [1]. - The patient's symptoms are dominated by respiratory and cardiovascular overload rather than fever. *TRALI* - **Transfusion-related acute lung injury (TRALI)** is characterized by acute respiratory distress with **hypoxemia** and **bilateral pulmonary infiltrates** due to non-cardiogenic pulmonary edema, typically associated with hypotension, not hypertension. - The prominent hypertension and the patient's underlying CKD make TACO a more likely diagnosis than TRALI.

Question 5: Anti-D prophylaxis is required in which of the following situations?

A. Routine antenatal visit at 20 weeks
B. Manual removal of placenta (Correct Answer)
C. Abortion at 63 days
D. Amniocentesis at 16 weeks

Explanation: ***Manual removal of placenta*** - Manual removal of placenta is a **sensitizing event** that carries a high risk of **feto-maternal hemorrhage** due to direct manipulation and potential placental disruption. - Anti-D prophylaxis is **mandatory** immediately following manual removal of placenta in all Rh-negative women to prevent **Rh alloimmunization**. - This is one of the most significant risk factors for maternal-fetal blood mixing requiring prophylaxis. *Routine antenatal visit at 20 weeks* - A routine antenatal visit at 20 weeks does **not** require anti-D prophylaxis. - Routine antenatal anti-D prophylaxis (RAADP) is recommended at **28 weeks** (and sometimes 34 weeks) of gestation for all Rh-negative pregnant women, not at routine 20-week visits. - The 20-week visit is typically for anatomical ultrasound screening, not for anti-D administration. *Abortion at 63 days* - While abortion at 63 days (approximately 9 weeks) **does require** anti-D prophylaxis, this is not the best answer. - Any spontaneous or induced abortion, especially after 12 weeks (though many guidelines recommend from 6-8 weeks onwards), requires anti-D prophylaxis in Rh-negative women. - However, compared to manual removal of placenta, this represents a lower volume sensitizing event. *Amniocentesis at 16 weeks* - While amniocentesis **does require** anti-D prophylaxis, this is not the best answer. - All invasive procedures (amniocentesis, CVS, cordocentesis) carry risk of fetal blood mixing with maternal circulation and require anti-D prophylaxis in Rh-negative women. - However, manual removal of placenta represents a higher risk scenario requiring immediate prophylaxis.

Question 6: Case of trauma in a patient with an unknown blood group. Patient is unstable and requires urgent blood transfusion. Which type of blood should be transfused?

A. O- (Correct Answer)
B. AB+
C. O+
D. A+

Explanation: ***O-*** - **O-negative blood** is considered the **universal donor** because it lacks A, B, and Rh (D) antigens, making it safe for transfusion to patients of any blood type in an emergency. - In a critically unstable patient with an unknown blood group requiring urgent transfusion, using **O-negative blood minimizes the risk of a severe acute hemolytic transfusion reaction**. *AB+* - **AB-positive blood** is the **universal recipient** blood type, meaning individuals with AB+ blood can receive blood from any donor. - However, transfusing AB+ blood to a patient with an unknown blood type could lead to a **severe hemolytic reaction** if the patient is not AB+. *O+* - While **O-positive blood** is common and can be given to individuals who are Rh-positive, it contains the **Rh antigen**. - Transfusing O-positive blood to an Rh-negative patient (whose Rh status is unknown in this emergency) could cause **alloimmunization** and a hemolytic reaction. *A+* - **A-positive blood** contains A antigens and Rh antigens. - Giving A-positive blood to a patient with an unknown blood type is risky, as it would cause a **hemolytic reaction** if the patient is B, AB, or O, or if they are Rh-negative.

Question 7: Which of the following components are involved in non-IgE mediated anaphylactic reactions?

A. Complement
B. Ig G
C. Ig M
D. All of the options (Correct Answer)

Explanation: ***All of the options*** - **Non-IgE mediated anaphylactic reactions** can involve various immune components beyond IgE, including **IgG**, **IgM**, and the **complement system**. - For instance, **IgG antibodies** can bind to mast cells or basophils and trigger degranulation, while **complement activation** can directly release anaphylatoxins, both leading to anaphylactoid symptoms. *Ig G* - While many anaphylactic reactions are **IgE-mediated**, **IgG antibodies** can also contribute to anaphylaxis, particularly in drug reactions or reactions to biologics. - **IgG-mediated anaphylaxis** often involves immune complexes that activate mast cells or basophils through Fcγ receptors. *Ig M* - **IgM antibodies** are less commonly implicated in direct anaphylactic reactions compared to IgE or IgG. - However, **IgM** can play a role in complex formation that activates the complement system, indirectly contributing to **anaphylactoid responses**. *Complement* - The **complement system** can be directly activated by certain drugs, physical stimuli, or immune complexes without the involvement of immunoglobulins. - This activation releases **anaphylatoxins (C3a, C4a, C5a)**, which can directly degranulate mast cells and basophils, leading to symptoms mimicking true anaphylaxis.

Question 8: Blood transfusion associated acute lung injury occurs due to -

A. Nosocomial infections
B. Auto-immune disorder
C. Genetic susceptibility
D. HLA-mediated reaction (Correct Answer)

Explanation: ***HLA-mediated reaction*** - Transfusion-related acute lung injury (TRALI) is primarily caused by **antibodies** in the donor plasma (usually anti-HLA or anti-HNA antibodies) reacting with the recipient's **neutrophils** [1]. - This interaction leads to neutrophil activation and sequestration in the pulmonary vasculature, causing **endothelial damage** and increased capillary permeability [1]. *Nosocomial infections* - Nosocomial infections are **hospital-acquired infections** and are not a direct cause of TRALI. - While infections can lead to lung injury, the mechanism of TRALI is distinct and immunologically mediated by donor antibodies. *Auto-immune disorder* - An autoimmune disorder involves the body's immune system attacking its own tissues, which is not the primary mechanism of TRALI. - TRALI is an **alloimmune reaction** where donor antibodies react with host antigens, rather than a pre-existing autoimmune condition. *Genetic susceptibility* - While genetic factors might sometimes play a role in an individual's general inflammatory response or susceptibility to certain conditions, they are **not the direct or primary cause** of TRALI. - The acute lung injury in TRALI is triggered by specific **antibody-antigen interactions** during the transfusion.

Question 9: What is the primary stimulus for erythropoietin production?

A. Increased temperature
B. Decreased blood pressure
C. Decreased plasma proteins
D. Tissue hypoxia (Correct Answer)

Explanation: ***Tissue hypoxia*** - Erythropoietin (EPO) production is primarily stimulated by sensing **low oxygen levels** in the kidneys. - This response is crucial for maintaining adequate oxygen delivery to tissues by increasing **red blood cell mass**. *Increased temperature* - An increase in body temperature is a stimulus for processes like **sweating** and **vasodilation**, to regulate body temperature. - It does not directly affect erythropoietin production or red blood cell synthesis. *Decreased blood pressure* - A decrease in blood pressure primarily stimulates the **renin-angiotensin-aldosterone system** and the release of **ADH** to regulate blood volume and pressure. - It does not directly cause an increase in erythropoietin release as its primary function is not related to oxygen sensing. *Decreased plasma proteins* - A decrease in plasma proteins primarily affects **oncotic pressure** and can lead to edema. - It is not a direct stimulus for erythropoietin production.

Question 10: What is the primary function of Langerhans' cells?

A. Antigen presenting cells (Correct Answer)
B. Involved in immune responses
C. Phagocytosis of pathogens
D. Keratinocyte production and maintenance

Explanation: ***Antigen presenting cells*** - Langerhans' cells play a critical role as **antigen presenting cells** (APCs) in the immune system, facilitating the activation of T-cells [1][2]. - They are found in the **epidermis** and are essential in initiating immune responses against pathogens [1][3]. *Seen in auto immune conditions* - While Langerhans' cells may be involved in autoimmune responses, they are not exclusively seen in these conditions. - Their primary function isn't linked to autoimmunity but rather to **immunological surveillance** and **antigen presentation** [1]. *Phagocytic cells* - Langerhans' cells are not primarily **phagocytic**, as their main role focuses on presenting antigens rather than directly engulfing pathogens [1]. - Phagocytic cells include macrophages and neutrophils, which are more involved in **directly consuming foreign particles**. *Seen in chronic infection* - Although Langerhans' cells can participate in the immune response during infections, they are not specifically characterized as being prominent in **chronic infections**. - Chronic infections are typically associated with different immune cell dynamics, involving other cells such as **plasma cells** and **T-cells**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 200. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 207-208. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, p. 1144.

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