MLT GlobeHematology: RBC indices & anemias – page 5
138 Hematology MCQs on RBC indices & anemias with answers and explanations.
A G6PD assay may be falsely normal when performed:
After hemolysis the oldest, most deficient cells are lost and young reticulocytes with higher G6PD remain. Repeat testing after about three months or use the reticulocyte-adjusted interpretation.
Which is NOT a recognized cause of macrocytosis?
Hypothyroidism, folate-antagonist drugs and alcohol raise the MCV. SLE causes anemia of chronic disease or immune hemolysis rather than a characteristic macrocytosis.
MCV 103 fL, normal B12 and folate, and round macrocytes with target cells on the film. The most likely cause is:
Round macrocytes and target cells with normal vitamins suggest liver disease or alcohol. Megaloblastic anemia requires deficient B12 or folate; iron deficiency and thalassemia are microcytic.
Which is NOT a cause of a raised red cell mass?
Erythrocytosis arises from primary marrow drive (JAK2) or increased erythropoietin from hypoxia or tumors. Iron overload does not increase red cell production.
Low MCV and MCH with a normal or high red cell count suggest:
Thalassemia produces many small, poorly hemoglobinized cells, so the RBC count is preserved. Megaloblastic anemia is macrocytic; aplastic anemia and leukemia are usually normocytic.
Which cause of gum abnormality produces tissue overgrowth rather than a bleeding tendency?
Phenytoin causes gingival hyperplasia. Thrombocytopenia and marrow failure cause bleeding gums, and vitamin C deficiency causes fragile vessels with swollen bleeding gums.
Which dietary factor decreases the absorption of non-heme iron?
Tannins and phytates bind iron into insoluble complexes. Ascorbic acid and gastric acid keep iron ferrous and soluble; meat enhances absorption. Iron deficiency itself increases absorption.
Macro-ovalocytes, hypersegmented neutrophils and raised methylmalonic acid with neurological symptoms indicate deficiency of:
Both B12 and folate deficiency cause megaloblastic anemia with hypersegmented neutrophils. Methylmalonic acid rises only in B12 deficiency, and neurological damage is a feature of B12 deficiency.
For a normocytic, normochromic sample, which set of results fails the 'rule of three' check and should be investigated?
The rule expects RBC × 3 ≈ Hb and Hb × 3 ≈ Hct (±3%). With RBC 3.5 and Hct 31%, Hb should be about 10.5 g/dL; 14.0 g/dL does not fit, suggesting an error such as lipemia.
A patient has microcytic anemia with a markedly raised RDW. Compared with thalassemia trait, this finding most favours:
Iron deficiency usually produces a heterogeneous population of cells (high RDW), whereas thalassemia trait usually shows uniform microcytes with a normal or only mildly raised RDW.
A patient has MCV 63 fL and RBC count 5.8 × 10^12/L. Using the Mentzer index, what is the result and interpretation?
Mentzer index = MCV ÷ RBC count = 63 ÷ 5.8 ≈ 10.9. A value below 13 favours thalassemia trait; above 13 favours iron deficiency. It is only a screening aid and must be confirmed.
In anemia of chronic inflammation, raised hepcidin causes anemia mainly by:
IL-6 stimulates hepatic hepcidin, which binds and degrades ferroportin. Iron cannot leave macrophages or enterocytes, so serum iron falls despite adequate stores.
A reticulocyte count is 6% and the hematocrit is 20%. Using a normal hematocrit of 45%, what is the corrected reticulocyte count?
Corrected retic = observed retic × (patient Hct ÷ normal Hct) = 6 × 20/45 = 2.7%. The correction removes the false rise caused by fewer circulating red cells.
An anemic patient has a reticulocyte production index (RPI) of 1.2. This most likely indicates:
An RPI below 2 in an anemic patient means the marrow is not responding adequately, e.g. iron deficiency, marrow failure or renal disease. An RPI above 3 suggests hemolysis or blood loss with a normal marrow.
The reticulocyte count is 2% and the RBC count is 3.0 × 10^12/L. What is the absolute reticulocyte count?
Absolute retic = retic fraction × RBC = 0.02 × 3.0 × 10^12/L = 0.06 × 10^12/L = 60 × 10^9/L. The absolute value avoids the error caused by anemia in percentage results.
Which metabolite is raised in BOTH vitamin B12 deficiency and folate deficiency?
Both B12 and folate are needed to remethylate homocysteine to methionine, so homocysteine rises in either deficiency. Methylmalonic acid rises only in B12 deficiency.
Neutrophil hypersegmentation is usually defined as:
Normally neutrophils have 2–5 lobes, with few five-lobed cells. More than 5% five-lobed cells or even one six-lobed cell is hypersegmentation, an early sign of megaloblastic anemia.
A patient with severe megaloblastic anemia has raised LDH and raised unconjugated bilirubin. These findings are mainly due to:
Many megaloblastic precursors die in the marrow before release (ineffective erythropoiesis), releasing LDH and hemoglobin breakdown products. This is intramedullary, not immune or complement-mediated hemolysis.
A patient with chronic alcohol use has MCV 106 fL with round macrocytes and target cells, no hypersegmented neutrophils and normal B12 and folate. This is best described as:
Alcohol and liver disease cause macrocytosis with round (not oval) macrocytes and target cells due to membrane lipid change. Absent hypersegmentation and normal vitamins argue against megaloblastic anemia.
A child with hereditary spherocytosis suddenly becomes very pale after a febrile illness, and the reticulocyte count falls to almost zero. The most likely cause is:
Parvovirus B19 infects erythroid progenitors (via the P antigen) and stops red cell production for about a week. In patients with shortened red cell survival this causes a transient aplastic crisis.