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Hematology
24 cards from 2 lessons in Hematology, each linking to the passage it came from.
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Anemia Evaluation and Microcytic and Macrocytic Anemias
What does MCV describe?
The average volume of the red cells.
An average can hide a mixture of small and large cells. Read it alongside RDW, the histogram, and the film.
What can an increased RDW reveal when the MCV is within the reference interval?
Variation in cell volume, including a mixed red-cell population.
Small and large cells can average to an MCV within the reference interval. RDW measures how much cell size varies and cannot name the cause.
How is the absolute reticulocyte count calculated from a percentage?
RBC count × reticulocyte percentage ÷ 100.
Keep the RBC count's volume unit. A low RBC count raises the percentage without more reticulocytes, so the absolute count shows the true marrow output.
What does an inadequate reticulocyte response in anemia suggest?
Insufficient or ineffective erythropoiesis.
Judge the count against how severe the anemia is and how long ago it began. In the first days after blood loss or hemolysis, the marrow may not yet have raised its output.
What typical iron-study pattern supports iron deficiency?
Low ferritin, low serum iron, increased TIBC, and low transferrin saturation.
Inflammation can raise ferritin and lower TIBC, hiding the pattern. Compare the iron studies with C-reactive protein, the CBC, and any known source of blood loss.
Why can ferritin be within or above the reference interval in iron deficiency?
Ferritin rises as part of an acute-phase response.
A ferritin in or above the reference interval can hide depleted stores. Read it with C-reactive protein or another inflammation marker and the transferrin saturation.
How does increased hepcidin restrict iron availability during inflammation?
It reduces ferroportin-mediated iron export from intestinal cells and macrophages.
Iron remains in storage cells, so less reaches plasma and developing erythrocytes. Ferritin can stay within the reference interval or rise.
Which RBC-count pattern can accompany marked microcytosis in thalassemia trait?
A relatively preserved or increased RBC count.
A high RBC count with microcytosis suggests thalassemia. Iron studies and hemoglobin analysis follow to confirm it, because the indices overlap and iron deficiency can coexist.
Which paired blood-film findings support megaloblastic hematopoiesis?
Macro-ovalocytes and hypersegmented neutrophils.
Impaired DNA synthesis delays nuclear maturation. The morphology does not show which vitamin is deficient, so confirm with vitamin B12 and folate tests.
Which metabolic marker helps distinguish vitamin B12 deficiency from isolated folate deficiency?
Methylmalonic acid.
Vitamin B12 supports methylmalonyl-CoA metabolism. Renal impairment and age can also increase methylmalonic acid.
Why does increased homocysteine fail to distinguish B12 deficiency from folate deficiency?
Either deficiency can impair homocysteine metabolism.
Renal function, B6 status, age, and medications also affect the result.
Why can a regenerative reticulocyte response raise MCV?
Reticulocytes are larger than mature red cells.
An increased proportion of these young cells can increase the population's average volume during recovery or hemolysis.
Read the passage: Nonmegaloblastic macrocytosis and spurious results
Differentials, Blood Film Morphology, and Indices
Where on a blood film should you assess routine red-cell morphology?
A representative monolayer where cells lie singly with preserved central pallor.
Thick areas and the extreme feather edge distort morphology. Survey the whole film before choosing the counting area.
Why are the margins and feather edge inspected separately from the differential count?
They may concentrate large abnormal cells or platelet clumps.
Scan them for these findings, then count in the monolayer, because a count taken at the edges overrepresents large cells.
What appearance defines a spherocyte on a well-prepared stained film?
A dense red cell without central pallor.
Spherocytes look the same in hereditary spherocytosis and in immune hemolysis, so the shape cannot tell the two apart.
What does a target cell look like on a stained film?
Central hemoglobin separated from an outer hemoglobin rim by a pale zone.
The target shape reflects excess membrane relative to cell volume and hemoglobin. It occurs in several hemoglobin and liver disorders.
How do echinocyte projections differ from acanthocyte projections?
Echinocyte spicules are regular and evenly spaced. Acanthocyte spicules are irregular in length, shape, and spacing.
Echinocytes are often a drying or pH artifact. Before reporting them, check that the film is well made and that they appear across the whole monolayer.
What process do schistocytes indicate?
Red-cell fragmentation.
Helmet and triangular fragments support mechanical or microangiopathic injury.
What is a Howell-Jolly body composed of?
Residual nuclear DNA.
These inclusions persist when splenic clearance is absent or reduced, and they can also accompany megaloblastic change.
Which stain confirms iron in suspected Pappenheimer bodies?
Prussian blue.
Pappenheimer bodies contain clustered iron granules. The iron stain separates them from other blue inclusions.
What does polychromasia usually represent on a Wright-stained film?
Young, RNA-rich red cells with blue-gray cytoplasm.
A reticulocyte count measures the marrow response that the film only estimates.
How do you calculate an absolute leukocyte-lineage count?
Total WBC count × the lineage percentage ÷ 100.
A low percentage can coexist with a normal absolute count when another lineage increases. Keep the total count's unit.
Which measurements and formula give MCHC in g/dL?
Hemoglobin in g/dL × 100 ÷ hematocrit in percent.
MCHC expresses hemoglobin concentration within the red-cell volume. An MCHC far above 38 g/dL is spurious, usually from lipemia, icterus, or marked leukocytosis interfering with the hemoglobin measurement.
Which two conditions can a positive Hb S solubility screen not tell apart?
Sickle cell trait and sickle cell disease.
Confirm with a hemoglobin method that identifies and quantifies the fractions. Age, transfusion, and a low Hb S fraction can cause false-negative screens.
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