Welcome to Part 40 of our Free ASCP MLS Exam Practice Questions series. In this section, we focus on Hemoglobinopathies and Thalassemia, two major groups of inherited red blood cell disorders that are frequently encountered in clinical practice and heavily tested in the ASCP MLS exam.
Understanding the structural and functional abnormalities of hemoglobin, along with the genetic basis of thalassemia syndromes, is essential for laboratory professionals.
🔹 Topics Covered in This Part
- Normal hemoglobin structure and variants
- Hemoglobinopathies: sickle cell disease, HbC, HbE, and other variants
- Thalassemia syndromes: alpha- and beta-thalassemia
- Clinical features and complications of hemoglobinopathies and thalassemias
- Laboratory diagnosis: electrophoresis, HPLC, genetic testing, and CBC findings
60 MCQs (3341-3400):
📘 How to Use These Practice Questions
- The questions in this section are designed to test your knowledge of hemoglobin structure, genetic mutations, and diagnostic evaluation.
- Numbering continues from the previous set — starting at Question 3341.
- Answer keys with explanations will follow at the end of the question set for review.
- What is the genetic basis of thalassemia?
a) A structural abnormality in the hemoglobin molecule
b) A decreased rate of globin chain synthesis
c) An absence of iron in the heme group
d) A decreased rate of heme synthesis - Hemoglobin H disease results from the deletion of how many alpha-globin genes?
a) 1 of 4
b) 2 of 4
c) 3 of 4
d) All 4 - Which hemoglobin variant migrates with HbS on alkaline electrophoresis but is not clinically sickling?
a) HbA
b) HbF
c) HbC
d) HbD - A patient has a normal hemoglobin level but microcytic red cells. Hemoglobin electrophoresis shows 70% HbA and 30% of a variant that migrates like HbA2. This is most consistent with:
a) HbC trait
b) HbE trait
c) HbO trait
d) HbD trait - Which hemoglobinopathy is characterized by the formation of rod-shaped crystals within red blood cells?
a) HbS
b) HbC
c) HbSC
d) HbD - The most appropriate screening test for the presence of hemoglobin S is:
a) Alkali denaturation test
b) Dithionite solubility test
c) Heat instability test
d) Isoelectric focusing - Hemoglobin Lepore results from a fusion product of which two genes?
a) Alpha and Beta
b) Gamma and Delta
c) Delta and Beta
d) Alpha and Gamma - In Hereditary Persistence of Fetal Hemoglobin (HPFH), there is a loss of expression of which globin chain?
a) Alpha
b) Beta
c) Gamma
d) Delta - Which hemoglobin is a tetramer of beta chains and is known as a “fast” hemoglobin on electrophoresis?
a) HbA
b) HbF
c) Hb Bart’s
d) HbH - In homozygous beta-thalassemia, which hemoglobin pattern is typically seen on electrophoresis?
a) Predominantly HbA with elevated HbA2
b) Predominantly HbS
c) Markedly increased HbF with absent or decreased HbA
d) Normal pattern with microcytosis - Which of the following is a characteristic finding in hemoglobin C disease?
a) Macrocytes
b) Spherocytes
c) Target cells
d) Rouleaux formation - A patient with beta-thalassemia minor would characteristically have:
a) A decreased red blood cell count
b) A high MCV
c) An increased HbA2 level
d) Decreased iron stores - Which hemoglobin variant is most common in Southeast Asian populations and migrates with HbC on alkaline gel?
a) HbD
b) HbE
c) HbO
d) HbG - The presence of HbH can be demonstrated by incubating red blood cells with:
a) Prussian blue stain
b) Brilliant cresyl blue
c) New methylene blue
d) Crystal violet - In sickle cell trait, the approximate percentage of HbS on electrophoresis is:
a) >90%
b) 70-80%
c) ~40%
d) <5% - What is the composition of Hemoglobin Bart’s?
a) Alpha2Delta2
b) Gamma4
c) Beta4
d) Alpha2Gamma2 - A false-negative result in the hemoglobin solubility test for HbS can be caused by:
a) A very high reticulocyte count
b) A severely decreased hematocrit
c) Using a specimen older than 2 hours
d) A high blood glucose level - Which of the following is true for Hemoglobin Constant Spring?
a) It is a short alpha-chain variant.
b) It is a fusion hemoglobin.
c) It is an elongated alpha-chain variant.
d) It is a beta-chain variant. - In a patient with heterozygous delta-beta thalassemia, what are the expected hemoglobin findings?
a) Normal HbA2, slightly elevated HbF
b) Elevated HbA2, normal Hb
c) Elevated HbA2, elevated HbF
d) Absent HbA, elevated HbF - Which of the following hemoglobins cannot be detected by the standard cyanmethemoglobin method?
a) Carboxyhemoglobin
b) Methemoglobin
c) Sulfhemoglobin
d) Deoxyhemoglobin - What is the primary defect in thalassemia?
a) Abnormal heme synthesis
b) Quantitative deficiency of globin chains
c) Structural instability of hemoglobin
d) Iron incorporation defect - A patient has 5% HbF (normal <2%) and a normal HbA2 level. This is most consistent with:
a) Alpha thalassemia minor
b) Beta thalassemia minor
c) Delta-beta thalassemia minor
d) Hereditary Persistence of Fetal Hemoglobin (HPFH) - Which hemoglobin variant has an increased oxygen affinity?
a) HbS
b) Hb Kansas
c) Hb Chesapeake
d) Hb Bibba - The Kleihauer-Betke test is used to quantify:
a) HbA2
b) HbS
c) HbF
d) HbH - Hemoglobin E is most commonly associated with which red cell morphology?
a) Macrocytic, normochromic
b) Normocytic, normochromic
c) Microcytic, hypochromic
d) Microcytic, normochromic - In the hemoglobin solubility test, turbidity indicates the presence of:
a) HbA
b) HbF
c) HbS
d) HbA2 - Hydrops fetalis is associated with the deletion of how many alpha-globin genes?
a) 1
b) 2
c) 3
d) 4 - Which of the following hemoglobins is unstable and may precipitate, forming Heinz bodies?
a) HbA
b) HbF
c) Hb Köln
d) HbA2 - In HbS, the amino acid substitution is:
a) Glutamic acid → Valine at position 6 on the beta chain
b) Valine → Glutamic acid at position 6 on the beta chain
c) Lysine → Glutamic acid at position 26 on the beta chain
d) Glutamic acid → Lysine at position 26 on the beta chain - Which laboratory finding is most characteristic of beta-thalassemia major?
a) Normal RBC count with macrocytosis
b) Increased RBC count with microcytosis and elevated HbF
c) Decreased RBC count with normocytosis
d) Marked polychromasia with spherocytes - The genetic mutation in sickle cell anemia involves:
a) Lysine replacing glutamic acid at position 6 of beta-globin
b) Valine replacing glutamic acid at position 6 of beta-globin
c) Deletion of alpha-globin gene
d) Duplication of delta-globin gene - Hemoglobin S polymerizes under:
a) Alkaline pH
b) Low oxygen tension
c) High temperature
d) Normal oxygen conditions - Which test is most specific for identifying hemoglobin variants?
a) Hemoglobin solubility test
b) Hemoglobin electrophoresis
c) Osmotic fragility test
d) Reticulocyte count - Sickle cell trait (heterozygous HbAS) is usually:
a) Clinically asymptomatic
b) Associated with severe anemia
c) Lethal in infancy
d) Associated with microcytosis only - Which inclusion body is commonly seen in splenectomized sickle cell patients?
a) Heinz bodies
b) Howell–Jolly bodies
c) Pappenheimer bodies
d) Basophilic stippling - The hallmark laboratory finding in β-thalassemia major is:
a) Increased HbA
b) Increased HbA2 and HbF
c) Increased HbC
d) Increased HbE - Alpha-thalassemia results from:
a) Mutations in beta-globin gene
b) Deletions in alpha-globin gene
c) Overproduction of HbF
d) Decreased synthesis of delta chains
Answer: b) Deletions in alpha-globin gene - Which form of alpha-thalassemia is incompatible with life?
a) Silent carrier (1 gene deletion)
b) Trait (2 gene deletions)
c) HbH disease (3 gene deletions)
d) Hydrops fetalis (4 gene deletions) - The most common hemoglobinopathy worldwide is:
a) HbC disease
b) HbS disease
c) Thalassemia trait
d) HbE trait - Which abnormal hemoglobin is resistant to malaria infection?
a) HbC
b) HbS
c) HbE
d) HbD - The “target cell” on a peripheral smear is often associated with:
a) Thalassemia and liver disease
b) Megaloblastic anemia
c) Iron deficiency anemia
d) Aplastic anemia - Which clinical feature is most typical of β-thalassemia major?
a) Mild anemia, asymptomatic
b) Severe anemia requiring transfusions
c) Petechiae and mucosal bleeding
d) Polycythemia - Which hemoglobin variant is caused by lysine replacing glutamic acid at position 6 of beta-globin?
a) HbS
b) HbC
c) HbE
d) HbD - HbE disease is most prevalent in:
a) Middle East
b) Africa
c) Southeast Asia
d) South America - Which thalassemia typically shows microcytic, hypochromic RBCs with normal iron studies?
a) Iron deficiency anemia
b) Beta-thalassemia trait
c) Sideroblastic anemia
d) Anemia of chronic disease - What is the major risk of repeated transfusions in thalassemia major?
a) Hemolysis
b) Iron overload
c) Pancytopenia
d) Megaloblastosis - Hemoglobin H disease is associated with:
a) Beta-chain tetramers
b) Alpha-chain tetramers
c) Gamma-chain tetramers
d) Delta-chain tetramers - Which RBC morphology is most commonly seen in HbH disease?
a) Spherocytes
b) Target cells and “golf ball” inclusions
c) Howell–Jolly bodies
d) Bite cells - Which laboratory test is used to confirm HbH inclusions?
a) Wright’s stain
b) Supravital stain (brilliant cresyl blue)
c) Prussian blue stain
d) PAS stain - Patients with sickle cell disease often present with:
a) Hemarthrosis
b) Vaso-occlusive crises
c) Petechiae
d) Splenomegaly only - Which hemoglobin has the highest affinity for oxygen?
a) HbA
b) HbS
c) HbF
d) HbC - The sickle solubility test is primarily used to detect:
a) HbF
b) HbA2
c) HbS
d) HbC - A patient with HbSC disease typically has:
a) Milder symptoms than HbSS
b) Identical severity as HbSS
c) Asymptomatic condition
d) Severe transfusion dependence - Which thalassemia condition produces elevated Hb Bart’s in newborn screening?
a) Beta-thalassemia minor
b) Alpha-thalassemia (major/hydrops fetalis)
c) HbC trait
d) HbE trait - The main distinguishing feature between iron deficiency anemia and thalassemia trait is:
a) Microcytosis in both
b) Ferritin levels (low in IDA, normal in thalassemia)
c) High HbA2 in IDA
d) Increased RDW in thalassemia - Hb Lepore is a result of:
a) Fusion of delta and beta genes
b) Deletion of alpha genes
c) Deletion of beta genes
d) Point mutation in gamma gene - Which test best evaluates the severity of thalassemia?
a) Serum ferritin
b) Hemoglobin electrophoresis
c) Reticulocyte count
d) Peripheral smear only - Splenic sequestration crisis is most common in:
a) HbC trait
b) Sickle cell disease
c) Beta-thalassemia trait
d) HbE disease - Which laboratory finding is consistent with thalassemia trait?
a) Normal or elevated RBC count despite anemia
b) Low RBC count and high RDW
c) High MCV and low ferritin
d) Low iron and low transferrin saturation - The best long-term treatment for β-thalassemia major is:
a) Repeated iron supplements
b) Bone marrow or stem cell transplantation
c) Splenectomy alone
d) Vitamin B12 injections
📌 How to Use This Practice Set
- Answer each question before checking the key.
- Focus on why the correct answer is right and the others are wrong.
- Use this set as timed practice to simulate the real exam environment.
Answer Key
Answer Key:
- b) A decreased rate of globin chain synthesis
- c) 3 of 4
- d) HbD
- b) HbE trait
- b) HbC
- b) Dithionite solubility test
- c) Delta and Beta
- b) Beta
- d) HbH
- c) Markedly increased HbF with absent or decreased HbA
- c) Target cells
- c) An increased HbA2 level
- b) HbE
- b) Brilliant cresyl blue
- c) ~40%
- b) Gamma4
- b) A severely decreased hematocrit
- c) It is an elongated alpha-chain variant.
- a) Normal HbA2, slightly elevated HbF
- c) Sulfhemoglobin
- b) Quantitative deficiency of globin chains
- c) Delta-beta thalassemia minor
- c) Hb Chesapeake
- c) HbF
- c) Microcytic, hypochromic
- c) HbS
- d) 4
- c) Hb Köln
- a) Glutamic acid → Valine at position 6 on the beta chain
- b) Increased RBC count with microcytosis and elevated HbF
- b) Valine replacing glutamic acid at position 6 of beta-globin
- b) Low oxygen tension
- b) Hemoglobin electrophoresis
- a) Clinically asymptomatic
- b) Howell–Jolly bodies
- b) Increased HbA2 and HbF
- b) Deletions in alpha-globin gene
- d) Hydrops fetalis (4 gene deletions)
- c) Thalassemia trait
- b) HbS
- a) Thalassemia and liver disease
- b) Severe anemia requiring transfusions
- b) HbC
- c) Southeast Asia
- b) Beta-thalassemia trait
- b) Iron overload
- a) Beta-chain tetramers
- b) Target cells and “golf ball” inclusions
- b) Supravital stain (brilliant cresyl blue)
- b) Vaso-occlusive crises
- b) HbS
- c) HbS
- a) Milder symptoms than HbSS
- b) Alpha-thalassemia (major/hydrops fetalis)
- b) Ferritin levels (low in IDA, normal in thalassemia)
- a) Fusion of delta and beta genes
- b) Hemoglobin electrophoresis
- b) Sickle cell disease
- a) Normal or elevated RBC count despite anemia
- b) Bone marrow or stem cell transplantation
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- Exam Name: MLS(ASCP)
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