G6PD deficiency MCQs With Answer

Introduction

G6PD deficiency MCQs With Answer is an essential revision resource for B. Pharm students studying pharmacology, hematology, and therapeutics. This concise, question-driven guide explores glucose-6-phosphate dehydrogenase deficiency pathophysiology, X-linked genetics, oxidative stress mechanisms, clinical features like hemolytic anemia and neonatal jaundice, diagnostic assays, and drug-induced hemolysis. Emphasis on drug interactions—primaquine, sulfonamides, dapsone—and safe medication choices helps future pharmacists apply evidence-based decisions. These targeted MCQs reinforce concepts such as pentose phosphate pathway role, Heinz bodies, bite cells, and management strategies. Questions focus on clinical scenarios, laboratory interpretation, and rational drug selection. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the primary biochemical role of glucose-6-phosphate dehydrogenase (G6PD) in red blood cells?

• Generate ATP via glycolysis
• Maintain reduced glutathione by producing NADPH
• Metabolize heme into bilirubin
• Transport oxygen bound to hemoglobin

Correct Answer: Maintain reduced glutathione by producing NADPH

Q2. Which pathway is G6PD the rate-limiting enzyme of?

• Glycolysis
• Tricarboxylic acid cycle
• Pentose phosphate pathway (hexose monophosphate shunt)
• Beta-oxidation of fatty acids

Correct Answer: Pentose phosphate pathway (hexose monophosphate shunt)

Q3. G6PD deficiency is inherited in which pattern?

• Autosomal dominant
• Autosomal recessive
• X-linked recessive

Correct Answer: X-linked recessive

Q4. Which red blood cell morphological finding is classically associated with G6PD deficiency after oxidative stress?

• Howell-Jolly bodies
• Heinz bodies and bite cells
• Schistocytes only

Correct Answer: Heinz bodies and bite cells

Q5. Why are young reticulocytes less susceptible to hemolysis in G6PD deficiency?

• They have increased hemoglobin affinity for oxygen
• They contain higher G6PD enzyme activity and more antioxidant capacity
• They lack mitochondria and thus avoid oxidative stress
• They are larger, preventing splenic sequestration

Correct Answer: They contain higher G6PD enzyme activity and more antioxidant capacity

Q6. Which laboratory pattern is typical during an acute hemolytic episode in G6PD deficiency?

• Decreased LDH, increased haptoglobin
• Increased LDH, decreased haptoglobin, increased indirect bilirubin
• Normal LDH and bilirubin
• Isolated increased conjugated bilirubin

Correct Answer: Increased LDH, decreased haptoglobin, increased indirect bilirubin

Q7. Which of the following is a reliable diagnostic test for quantifying G6PD enzyme activity?

• Complete blood count alone
• Fluorescent spot test (qualitative)
• Spectrophotometric quantitative enzyme assay
• Direct Coombs test

Correct Answer: Spectrophotometric quantitative enzyme assay

Q8. Why can G6PD enzyme assay be falsely normal immediately after a hemolytic episode?

• Older RBCs dominate and have higher enzyme levels
• Recent transfusion introduces donor RBCs with normal G6PD
• Young RBCs and reticulocytes with higher G6PD skew the result upward
• The assay measures DNA, not enzyme activity

Correct Answer: Young RBCs and reticulocytes with higher G6PD skew the result upward

Q9. Which population groups have higher prevalence of G6PD deficiency?

• Scandinavian and Inuit populations
• Sub-Saharan African, Mediterranean, Middle Eastern, and certain Asian populations
• Native American populations exclusively
• All populations have equal prevalence globally

Correct Answer: Sub-Saharan African, Mediterranean, Middle Eastern, and certain Asian populations

Q10. Favism, acute hemolysis after ingesting fava beans, is associated with deficiency of which enzyme?

• Pyruvate kinase
• Glucose-6-phosphate dehydrogenase (G6PD)
• Glutathione peroxidase
• Aldolase

Correct Answer: Glucose-6-phosphate dehydrogenase (G6PD)

Q11. Which of the following drugs is a classic cause of hemolysis in G6PD-deficient patients?

• Acetaminophen
• Primaquine
• Amoxicillin
• Metformin

Correct Answer: Primaquine

Q12. Rasburicase is contraindicated in G6PD deficiency because it can cause:

• Hyperuricemia
• Oxidative hemolysis and methemoglobinemia
• Platelet aggregation
• Renal tubular necrosis only

Correct Answer: Oxidative hemolysis and methemoglobinemia

Q13. Which of these antibiotics is most likely to precipitate hemolysis in a G6PD-deficient patient?

• Penicillin
• Sulfonamides (e.g., sulfamethoxazole)
• Cephalexin
• Azithromycin

Correct Answer: Sulfonamides (e.g., sulfamethoxazole)

Q14. How does oxidative stress lead to hemolysis in G6PD-deficient RBCs?

• Oxidants cause direct DNA damage in RBCs
• Inability to regenerate reduced glutathione allows oxidative denaturation of hemoglobin and membrane damage
• Oxidants inhibit hemoglobin synthesis causing anemia
• Oxidative stress triggers autoimmune hemolysis

Correct Answer: Inability to regenerate reduced glutathione allows oxidative denaturation of hemoglobin and membrane damage

Q15. In neonates, G6PD deficiency most commonly presents as:

• Persistent conjugated hyperbilirubinemia
• Severe unconjugated hyperbilirubinemia and risk of kernicterus
• Neutropenia
• Thrombocytopenia

Correct Answer: Severe unconjugated hyperbilirubinemia and risk of kernicterus

Q16. Which morphological RBC change is formed by denatured hemoglobin attached to the membrane?

• Basophilic stippling
• Howell-Jolly bodies
• Heinz bodies
• Spherocytes

Correct Answer: Heinz bodies

Q17. Female carriers of G6PD mutations may show variable expression due to:

• Autosomal dominant transmission
• Skewed X-chromosome inactivation (lyonization)
• Maternal imprinting
• Haploinsufficiency of autosomal genes

Correct Answer: Skewed X-chromosome inactivation (lyonization)

Q18. Which WHO classification grade indicates the most severe G6PD deficiency with chronic hemolysis?

• Class V
• Class II
• Class I
• Class IV

Correct Answer: Class I

Q19. What is the expected reticulocyte response after an acute hemolytic episode in G6PD deficiency?

• Reticulocytopenia
• Marked reticulocytosis as bone marrow compensates
• No change in reticulocyte count
• Transient aplastic crisis instead of reticulocytosis

Correct Answer: Marked reticulocytosis as bone marrow compensates

Q20. The fluorescent spot test screens for G6PD deficiency by detecting:

• Glutathione levels directly
• Conversion of NADP to NADPH producing fluorescence
• Presence of Heinz bodies in stained smear
• Hemoglobin oxidation state

Correct Answer: Conversion of NADP to NADPH producing fluorescence

Q21. Which clinical sign is most suggestive of intravascular hemolysis in G6PD deficiency?

• Splenomegaly only
• Dark or tea-colored urine due to hemoglobinuria
• Isolated lymphadenopathy
• Conjugated hyperbilirubinemia

Correct Answer: Dark or tea-colored urine due to hemoglobinuria

Q22. Which of the following is considered a safe analgesic/antipyretic choice for a G6PD-deficient patient?

• High-dose aspirin
• Acetaminophen (paracetamol) at therapeutic doses
• Phenazopyridine
• Methylene blue

Correct Answer: Acetaminophen (paracetamol) at therapeutic doses

Q23. Which hemoglobin test is useful to demonstrate Heinz bodies?

• Giemsa stain only
• Supravital stain (e.g., crystal violet) on peripheral smear
• Direct Coombs test
• Serum electrophoresis

Correct Answer: Supravital stain (e.g., crystal violet) on peripheral smear

Q24. A B. Pharm student should counsel patients with G6PD deficiency to avoid which class of drugs commonly used for urinary tract infections?

• Beta-lactams
• Nitrofurantoin and sulfonamides
• Macrolides
• Aminoglycosides

Correct Answer: Nitrofurantoin and sulfonamides

Q25. When managing severe hemolysis in G6PD deficiency, which immediate treatment is often required?

• Exchange transfusion for mild anemia
• Supportive care including hydration and blood transfusion if needed
• High-dose corticosteroids as first-line
• Iron chelation therapy

Correct Answer: Supportive care including hydration and blood transfusion if needed

Q26. Which statement about newborn screening for G6PD deficiency is correct?

• It is unnecessary because neonatal jaundice is always mild
• Early screening helps prevent kernicterus by guiding phototherapy decisions
• Screening always detects female heterozygotes reliably
• Screening measures only hemoglobin levels

Correct Answer: Early screening helps prevent kernicterus by guiding phototherapy decisions

Q27. Which of the following metabolic consequences occurs due to decreased NADPH in RBCs?

• Increased regeneration of reduced glutathione
• Failure to detoxify peroxides leading to oxidative damage
• Enhanced fatty acid synthesis in RBCs
• Increased pentose production for DNA synthesis in RBCs

Correct Answer: Failure to detoxify peroxides leading to oxidative damage

Q28. Which historical fact explains selective advantage of G6PD deficiency alleles in certain regions?

• Protection against severe malaria (Plasmodium falciparum)
• Resistance to tuberculosis
• Increased fertility rates
• Better nutritional absorption

Correct Answer: Protection against severe malaria (Plasmodium falciparum)

Q29. Which lab value is typically low during intravascular hemolysis?

• Indirect bilirubin
• Haptoglobin
• Reticulocyte count
• Lactate dehydrogenase (LDH)

Correct Answer: Haptoglobin

Q30. A patient with suspected G6PD deficiency had a normal enzyme assay during acute hemolysis. The best next step is:

• Declare the patient non-deficient and stop follow-up
• Repeat quantitative assay after recovery of hematologic status (several weeks)
• Perform bone marrow biopsy immediately
• Start lifelong antioxidant therapy without further testing

Correct Answer: Repeat quantitative assay after recovery of hematologic status (several weeks)

Q31. Which mutation type most commonly causes G6PD deficiency?

• Large chromosomal deletion
• Point mutations in the G6PD gene leading to enzyme variants
• Triplet repeat expansion
• Mitochondrial DNA mutation

Correct Answer: Point mutations in the G6PD gene leading to enzyme variants

Q32. Which of the following clinical scenarios should alert a pharmacist to suspect G6PD deficiency?

• Patient with anemia responding to iron therapy
• Patient with acute onset dark urine and jaundice after taking primaquine
• Chronic bleeding with low platelets
• Asymptomatic mild leukocytosis

Correct Answer: Patient with acute onset dark urine and jaundice after taking primaquine

Q33. Which over-the-counter medication is explicitly avoided in G6PD deficiency due to oxidative potential?

• Ibuprofen
• Phenazopyridine
• Acetaminophen
• Loperamide

Correct Answer: Phenazopyridine

Q34. In pharmacology, why must pharmacists be aware of G6PD status before prescribing dapsone?

• Dapsone has no hematologic effects in any patient
• Dapsone can cause dose-related oxidative hemolysis and methemoglobinemia in G6PD-deficient patients
• Dapsone enhances G6PD enzyme activity
• Dapsone only affects platelet function

Correct Answer: Dapsone can cause dose-related oxidative hemolysis and methemoglobinemia in G6PD-deficient patients

Q35. Which biochemical marker increases due to red cell destruction and hemoglobin breakdown?

• Haptoglobin increases
• Indirect (unconjugated) bilirubin increases
• Direct bilirubin increases exclusively
• Serum albumin drastically rises

Correct Answer: Indirect (unconjugated) bilirubin increases

Q36. Which of the following is a non-drug trigger known to precipitate hemolysis in G6PD deficiency?

• Prolonged fasting
• Ingestion of fava beans (favism)
• Exposure to high altitude only
• Excessive vitamin D intake

Correct Answer: Ingestion of fava beans (favism)

Q37. Which cell-processing event produces “bite cells” seen in G6PD deficiency?

• Splenic macrophages removing Heinz bodies from RBCs
• Bone marrow fragmentation of RBCs
• Immune complex deposition on RBCs
• RBCs undergoing apoptosis in circulation

Correct Answer: Splenic macrophages removing Heinz bodies from RBCs

Q38. For a heterozygous female, which test can better identify mosaic G6PD activity than standard quantitative assay?

• Peripheral smear alone
• DNA molecular analysis (mutation-specific PCR) and functional single-cell assays
• Urine dipstick test
• Serum iron studies

Correct Answer: DNA molecular analysis (mutation-specific PCR) and functional single-cell assays

Q39. Which pharmacologic agent is safe and recommended for malaria prophylaxis in known G6PD-deficient individuals?

• Primaquine for relapse prevention
• Chloroquine (where sensitive) or atovaquone-proguanil depending on region and resistance patterns
• Treatment with high-dose dapsone
• Methylene blue prophylaxis

Correct Answer: Chloroquine (where sensitive) or atovaquone-proguanil depending on region and resistance patterns

Q40. During counseling, which instruction is most important for patients newly diagnosed with G6PD deficiency?

• Avoid all vaccinations
• Maintain a list of avoided oxidant drugs and substances and inform all healthcare providers
• Immediately start daily antioxidants without guidance
• Stop eating all legumes indefinitely

Correct Answer: Maintain a list of avoided oxidant drugs and substances and inform all healthcare providers

Q41. Which laboratory finding would help differentiate G6PD-related hemolysis from autoimmune hemolysis?

• Positive direct antiglobulin (Coombs) test in G6PD deficiency
• Negative direct Coombs test and presence of Heinz bodies suggests G6PD deficiency
• Elevated ESR specific to G6PD deficiency
• High serum ferritin diagnostic for G6PD deficiency

Correct Answer: Negative direct Coombs test and presence of Heinz bodies suggests G6PD deficiency

Q42. Which form of bilirubin increases the risk of kernicterus in neonates with G6PD deficiency?

• Conjugated (direct) bilirubin
• Unconjugated (indirect) bilirubin
• Delta bilirubin
• Fractionated bilirubin is not relevant

Correct Answer: Unconjugated (indirect) bilirubin

Q43. Which enzyme level comparison helps confirm a diagnosis of G6PD deficiency in males?

• G6PD activity lower than normal reference range in a male patient
• Elevated G6PD activity is diagnostic
• Comparison of G6PD to PK (pyruvate kinase) ratio
• Measurement of DNA methylation patterns

Correct Answer: G6PD activity lower than normal reference range in a male patient

Q44. Which pharmacologic agent used to treat methemoglobinemia is contraindicated in G6PD deficiency?

• Methylene blue
• High-flow oxygen
• Ascorbic acid (vitamin C) as adjunct
• Exchange transfusion if severe

Correct Answer: Methylene blue

Q45. Which public health measure is useful in regions with high prevalence of G6PD deficiency?

• Universal prescription of primaquine to all residents
• Newborn screening programs and clinician/pharmacist education about contraindicated drugs
• Banning all legumes
• Routine administration of rasburicase to cancer patients

Correct Answer: Newborn screening programs and clinician/pharmacist education about contraindicated drugs

Q46. Which of the following best explains why G6PD-deficient erythrocytes are more susceptible to oxidative drugs?

• They have increased membrane cholesterol making them rigid
• They lack mitochondria to detoxify oxidants
• They cannot generate NADPH required to maintain reduced glutathione
• They contain excess hemoglobin S

Correct Answer: They cannot generate NADPH required to maintain reduced glutathione

Q47. Which common laboratory parameter is NOT typically a direct diagnostic indicator of G6PD deficiency?

• G6PD enzyme activity assay
• Genetic testing for G6PD mutations
• Complete blood count alone without specific enzyme testing
• Fluorescent spot test

Correct Answer: Complete blood count alone without specific enzyme testing

Q48. Which drug used for urinary analgesia should be avoided due to oxidative potential causing hemolysis in G6PD deficiency?

• Phenazopyridine
• Ibuprofen
• Acetaminophen
• Diphenhydramine

Correct Answer: Phenazopyridine

Q49. A patient with known G6PD deficiency requires analgesia and antipyresis. Which is the best pharmacist recommendation?

• Recommend phenazopyridine for comfort
• Recommend acetaminophen for pain and fever at recommended doses
• Recommend starting dapsone for analgesia
• Recommend methylene blue to prevent hemolysis

Correct Answer: Recommend acetaminophen for pain and fever at recommended doses

Q50. Which educational point will most reduce medication-related hemolysis risk in G6PD-deficient patients?

• Telling patients to double doses if symptoms persist
• Providing a personalized list of contraindicated oxidant drugs and instructing to seek medical advice before new medications
• Advising to avoid all antibiotics permanently
• Encouraging self-medication with herbal oxidants

Correct Answer: Providing a personalized list of contraindicated oxidant drugs and instructing to seek medical advice before new medications

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com