MLT GlobeHematology: RBC indices & anemias – page 2
138 Hematology MCQs on RBC indices & anemias with answers and explanations.
A woman with long-standing heavy menstrual loss would most likely show which red cell appearance on the smear?
Chronic blood loss causes iron deficiency, reducing hemoglobin synthesis and producing microcytic hypochromic cells, often with pencil cells. Microspherocytes suggest spherocytosis or immune hemolysis.
Marrow failure after high-dose exposure to ionizing radiation typically produces:
Radiation kills dividing hematopoietic stem and progenitor cells, leaving a hypocellular marrow and pancytopenia. It does not cause iron-deficient or megaloblastic changes.
A positive direct antiglobulin test indicates:
The DAT adds anti-human globulin directly to washed patient cells, detecting in vivo sensitization. Free serum antibody is detected by the indirect antiglobulin test.
Besides hereditary spherocytosis, numerous spherocytes on a blood film are typical of:
IgG-coated red cells lose membrane to splenic macrophages and become spherocytes. The DAT separates immune from hereditary spherocytosis.
A healthy adult's mean cell hemoglobin (MCH) is expected to fall within about:
MCH = Hb ÷ RBC count, normally about 27–32 pg. Low values indicate hypochromia (iron deficiency, thalassemia); high values accompany macrocytosis.
Which anemia is NOT microcytic?
Pernicious anemia causes B12 deficiency and a macrocytic megaloblastic anemia. The others impair heme or globin synthesis, producing small cells.
A battery-factory worker has anemia with coarse basophilic stippling of red cells. The most likely cause is:
Lead inhibits pyrimidine 5'-nucleotidase, so ribosomal RNA aggregates as coarse stippling, and it blocks heme synthesis. Stippling may also occur in thalassemia.
Anemia is defined in the laboratory by:
Anemia means reduced oxygen-carrying capacity, measured as low hemoglobin. MCV classifies anemia but does not define it.
Which set of results favors iron deficiency anemia?
Iron deficiency lowers serum iron and ferritin while transferrin synthesis rises, increasing TIBC. Normal iron studies with microcytosis suggest thalassemia trait.
Which condition would NOT be expected to raise the MCV?
Iron deficiency causes microcytosis. Folate and B12 deficiency produce macrocytes, and large reticulocytes can raise the MCV after hemorrhage or hemolysis.
A patient has a hematocrit of 0.30 L/L (30%) and an RBC count of 4.0 × 10^12/L. What is the MCV?
MCV (fL) = Hct (%) × 10 ÷ RBC (× 10^12/L) = 300 ÷ 4.0 = 75 fL. 133 fL results from dividing the RBC count by the hematocrit incorrectly.
Hemoglobin is 9.0 g/dL (90 g/L) and the RBC count is 3.0 × 10^12/L. What is the MCH?
MCH (pg) = Hb (g/dL) × 10 ÷ RBC (× 10^12/L) = 90 ÷ 3.0 = 30 pg. 10 pg comes from forgetting to multiply the hemoglobin by 10.
Hemoglobin is 12.0 g/dL and hematocrit is 36%. What is the MCHC?
MCHC (g/dL) = Hb (g/dL) × 100 ÷ Hct (%) = 1200 ÷ 36 = 33.3 g/dL (333 g/L), which is within the normal range.
What does the red cell distribution width (RDW) measure?
RDW is the coefficient of variation (or SD) of the RBC volume distribution, so it is a numerical measure of anisocytosis. It does not measure shape (poikilocytosis) or hemoglobin content.
Which laboratory test is the earliest to become abnormal as body iron stores are depleted?
Ferritin falls first because it reflects storage iron. Serum iron and transferrin saturation fall later (iron-deficient erythropoiesis), and Hb and MCV fall last when anemia develops.
The typical bone marrow change in megaloblastic anemia is:
Impaired DNA synthesis delays nuclear development while hemoglobinization of the cytoplasm continues, giving large cells with open 'young' chromatin and mature cytoplasm (nuclear–cytoplasmic asynchrony).
A fisherman who often eats raw freshwater fish develops macrocytic anemia with hypersegmented neutrophils. Which parasite is the likely cause?
The fish tapeworm Diphyllobothrium latum competes for vitamin B12 in the gut and can cause B12 deficiency. Hookworm (Necator) causes blood loss and microcytic iron deficiency instead.
Which drug most commonly causes megaloblastic change by inhibiting dihydrofolate reductase?
Methotrexate blocks dihydrofolate reductase, reducing active folate and DNA synthesis. Proton-pump inhibitors can reduce B12 absorption over years, but they do not act on folate metabolism.
A 25-year-old has pancytopenia, a reticulocyte count of 0.2% and a bone marrow trephine that is mostly fat with few hematopoietic cells. No abnormal cells are seen. The most likely diagnosis is:
Pancytopenia with very low reticulocytes and a hypocellular fatty marrow without infiltration is aplastic anemia. Megaloblastic anemia and leukemia usually give a hypercellular marrow.
Which antibiotic is classically associated with idiosyncratic aplastic anemia?
Chloramphenicol causes a dose-related reversible marrow suppression and a rare, often fatal, idiosyncratic aplastic anemia. The other antibiotics are not classic causes.