Hematology

Calculate and check blood counts, read the blood film, and interpret anemia, leukocyte, platelet, and coagulation findings before reporting.

Steps

1
Red-cell indices13 min
4 skills
- Calculate MCV using the stated hematocrit and RBC units
- Calculate MCH using the stated hemoglobin and RBC units
- Calculate MCHC from hemoglobin and hematocrit
- Calculate RDW-CV from the standard deviation of red-cell volume and the MCV
2
How analyzers count cells and measure hemoglobin13 min
3 skills
- Explain how an impedance or optical analyzer counts cells and what it can miscount
- Recognize and correct turbidity that falsely raises a photometric hemoglobin
- Recognize trapped plasma, sealing, and spinning errors in a microhematocrit
3
Reticulocyte counts and the marrow response14 min
4 skills
- Calculate a manual reticulocyte percentage
- Calculate a reticulocyte percentage using the stated Miller-reticle area ratio
- Calculate the absolute reticulocyte count from RBC count and reticulocyte percent
- Judge whether the reticulocyte response is adequate for the anemia
At the bench Relate red cell indices and morphology to the anemia workup
4
Chamber counts and the NRBC correction13 min
4 skills
- Calculate the volume counted in a hemacytometer
- Calculate a cell concentration from a chamber count and dilution
- Correct a WBC count that still includes nucleated red cells
- Keep nucleated red cells out of the white-cell differential denominator
At the bench Classify cells and describe morphology in a manual differential
5
The white-cell differential15 min
4 skills
- Choose a suitable blood-film area and inspect the margins separately
- Classify leukocytes from the features visible on a blood film
- Recognize the usual adult proportions and absolute counts of each white-cell type
- Calculate an absolute leukocyte-lineage count
At the bench Classify cells and describe morphology in a manual differential
6
Red-cell production, clearance and oxygen delivery15 min
4 skills
- Match hematopoietic growth factors to the lineages and stages they support
- Order erythroid precursors by stage from their nuclear and cytoplasmic features
- Trace how macrophages clear aged red cells and return their iron for reuse
- Predict the direction of a hemoglobin oxygen-affinity shift
7
Microcytic anemias and iron studies15 min
4 skills
- Classify an anemia pattern using MCV and RDW
- Explain how hepcidin gives low serum iron with normal or high ferritin in inflammation
- Recognize microcytosis with a preserved RBC count that needs hemoglobin fractionation
- Recognize iron deficiency on iron studies, including when ferritin is not low
At the bench Relate red cell indices and morphology to the anemia workup
8
Macrocytic anemias15 min
4 skills
- Tell vitamin B12 from folate deficiency with methylmalonic acid and homocysteine
- Recognize a raised MCV caused by a high reticulocyte count
- Recognize a vitamin B12 deficiency pattern from the CBC, film, and B12 result
- Recognize polychromatophilic cells as young red cells on a Wright-stained film
At the bench Relate red cell indices and morphology to the anemia workup
9
Recognizing hemolysis and its mechanism15 min
4 skills
- Recognize hemolysis from haptoglobin, indirect bilirubin, LDH, and reticulocyte results
- Tell immune, fragmentation, and intrinsic hemolysis apart using the DAT and film
- Recognize when a normal G6PD result cannot exclude deficiency
- Recognize a spherocyte in the monolayer of a blood film
At the bench Relate red cell indices and morphology to the anemia workup
10
Red-cell shapes on the film14 min
4 skills
- Recognize the central staining pattern of a target cell
- Distinguish echinocyte projections from acanthocyte projections
- Recognize schistocytes and the percentage that suggests thrombotic microangiopathy
- Recognize a Howell-Jolly body as a nuclear remnant
At the bench Relate red cell indices and morphology to the anemia workup
11
Inclusions, sickling screens, erythrocytosis and the ESR15 min
4 skills
- Choose an iron stain to confirm suspected Pappenheimer bodies
- Report a positive Hb S solubility screen without calling trait or disease
- Choose between a repeat count, EPO, and JAK2 V617F for a raised hemoglobin
- Recognize how citrate ratio, anemia, tube tilt, and temperature change a Westergren ESR
At the bench Relate red cell indices and morphology to the anemia workup
12
Reactive white-cell patterns and inherited anomalies15 min
4 skills
- Recognize reactive neutrophilia from a left shift and toxic changes
- Recognize a heterogeneous reactive lymphocyte population
- Distinguish an inherited leukocyte anomaly from a reactive or clonal change
- Report a CBC and film as compatible with a disorder until confirming tests are done
At the bench Recognize abnormal cell findings that need further review
13
Chronic myeloid leukemia15 min
3 skills
- Recognize a broad myeloid maturation spectrum in a CML-compatible pattern
- Identify the genetic finding that establishes CML
- Assign a CML phase from blast and basophil percentages under WHO5 or ICC
At the bench Recognize abnormal cell findings that need further review
14
Blasts on the film and cytochemistry15 min
3 skills
- Recognize myeloblasts and Auer rods that call for an acute myeloid leukemia workup
- Recognize lymphoblasts that call for an acute lymphoblastic leukemia workup
- Match an MPO, Sudan black B, or esterase pattern to blast lineage
At the bench Recognize abnormal cell findings that need further review
15
Classifying acute leukemia15 min
3 skills
- Name the cytogenetic and molecular tests needed to classify a suspected AML
- Name the immunophenotype and genetic tests needed to classify a suspected ALL
- Assign a cell population's lineage from its full flow cytometry marker pattern
At the bench Recognize abnormal cell findings that need further review
16
Small mature lymphocytes, CLL and MBL14 min
2 skills
- Recognize a small mature lymphocytosis that needs flow cytometry for clonality
- Name the flow cytometry result that separates CLL from monoclonal B-cell lymphocytosis
At the bench Recognize abnormal cell findings that need further review
17
Choosing and reading molecular tests15 min
2 skills
- Choose FISH, karyotype, or a molecular test for the change being sought
- Calculate an expected variant allele fraction from the abnormal-cell fraction
18
Platelet counts and platelet function15 min
4 skills
- Check the film for platelet clumps before reporting a low platelet count
- Classify a low platelet count as reduced production, consumption, or sequestration
- Tell reactive from clonal thrombocytosis using the cause, film, and driver mutations
- Tell Bernard-Soulier from Glanzmann by platelet size, count, and aggregation results
At the bench Resolve analyzer flags before releasing a blood count
19
Clot formation, fibrinolysis and the citrate tube15 min
3 skills
- Trace thrombin generation from tissue factor and factor VIIa to the platelet surface
- Trace how plasmin forms, is inhibited, and breaks cross-linked fibrin into D-dimer
- Reject a coagulation specimen with the wrong fill, hematocrit, handling, or timing
At the bench Review coagulation results and identify the next laboratory check
20
PT, APTT and mixing studies15 min
4 skills
- Read a PT and APTT result pair to choose the next coagulation test
- Interpret immediate and incubated mixing-study behavior
- Match an isolated prolonged APTT to factor VIII, IX, XI, or contact-factor deficiency
- Choose a one-stage or chromogenic factor assay and check its dilution linearity
At the bench Review coagulation results and identify the next laboratory check
21
Inhibitors, lupus anticoagulant and thrombophilia timing15 min
4 skills
- Interpret a Nijmegen-Bethesda titer with the inhibitor type and its kinetics
- Interpret lupus anticoagulant screen, mix, and confirm results from two test systems
- Recognize when anticoagulants or acute illness make a thrombophilia result unreliable
- Use thrombin and reptilase times to separate heparin from a fibrinogen defect
At the bench Review coagulation results and identify the next laboratory check
22
Von Willebrand, HIT, DIC and anticoagulant assays15 min
4 skills
- Classify a von Willebrand panel from antigen, activity ratio, and factor VIII
- Sequence HIT immunoassay and functional testing by pretest probability
- Recognize the platelet, PT, D-dimer, and fibrinogen changes that suggest DIC
- Choose the calibrated assay that measures a stated heparin or direct oral anticoagulant
At the bench Review coagulation results and identify the next laboratory check

More skills in this part

Hematology

Systematic microscopic film examination

In the lab

The flagged CBCAbout 18 to 28 minutes

Microscope

WBC0 / 100MANUAL DIFF ORDEREDPeripheral blood differentialPerform manual diff Inside a CBCRun the CBC Set up the microscopeAdjust the light Study reactive neutrophiliaOpen teaching slides

Bench references

Iron study patterns

Deficiency, inflammation, mixed findings, and overload

Interpret the iron panel results together. Serum iron reflects circulating iron, and ferritin helps assess storage iron. Inflammation can sequester iron in storage and raise ferritin, so little iron is available for red cell production.

Total iron-binding capacity (TIBC) reflects transferrin, the main iron transport protein. Transferrin saturation (TSAT) is the percentage of that capacity occupied by iron.

TSAT (%) = serum iron ÷ TIBC × 100

Use the same concentration units for iron and TIBC.

Iron 30 µg/dL ÷ TIBC 300 µg/dL × 100 = 10% TSAT. µg/dL = micrograms per deciliter. A low TSAT occurs in both iron deficiency and inflammation.

Typical adult patterns

↓ decreased; ↑ increased; N within the applicable reference interval.

Pattern	Serum iron	TIBC / transferrin	TSAT	Ferritin
Iron deficiency	decreased	increased	decreased	decreased
Anemia of inflammation	decreased	decreased or normal	decreased or normal	normal or increased
Mixed deficiency + inflammation	decreased	Variable, often normal or decreased	decreased	decreased, normal, or increased
Iron overload	Often increased	normal or decreased	Usually increased	Usually increased

Why inflammation changes the panel

A low ferritin supports depleted stores. During inflammation, a normal or high ferritin cannot exclude deficiency, and liver injury can also raise ferritin. Hepcidin, an iron-regulating hormone, reduces iron release from stores and absorption from the gut. Inflammation can also lower transferrin. Mixed deficiency may then lack the high TIBC and low ferritin expected in iron deficiency.

High ferritin alone does not establish overload. A persistently high TSAT makes overload more likely. Some overload disorders have a normal TSAT, so a normal value does not exclude overload.

When results do not agree

Compare with hemoglobin, red cell indices, C-reactive protein or another inflammation marker, and collection and iron-treatment history.

Soluble transferrin receptor may help when inflammation obscures ferritin. Increased red cell production also raises it, and cutoffs vary by method. Reticulocyte hemoglobin reflects the iron available to recently produced red cells. It can be low in either deficiency or inflammation.

Hematology03 / 10Iron study patternsDeficiency, inflammation, mixed findings, and overload

PT and APTT patterns

Screening patterns, specimen checks, and mixing studies

Prothrombin time (PT) and activated partial thromboplastin time (APTT) measure the clotting time of citrated plasma after activation by different reagents. Some factors are measured by both tests, so one time or both can be prolonged.

PT · tissue factor / extrinsic arm
VII

APTT · contact / intrinsic arm
XII → XI → IX + VIII

Common: X + V → thrombin (activated II) → fibrin formation

Assay schematic. Roman numerals identify the factors. Factors V and VIII are cofactors. Thrombin cleaves fibrinogen to fibrin. Contact activation also needs prekallikrein and high-molecular-weight kininogen.

Patterns and possible explanations

Screening pattern	Possibilities to investigate	Distinguishing findings
PT prolonged APTT in range	VII deficiency/inhibitor; early vitamin K deficiency or warfarin.	Also possible with liver disease or direct factor Xa inhibitors.
APTT prolonged PT in range	VIII, IX, XI, or contact-factor deficiency/inhibitor; heparin; direct thrombin inhibitor (for example, dabigatran); lupus anticoagulant.	Contact-factor deficiency usually causes no bleeding. Lupus anticoagulant can accompany thrombosis.
Both prolonged	Common/multiple-factor deficiency: vitamin K deficiency, liver disease, or disseminated intravascular coagulation; anticoagulants.	Compare with platelets, fibrinogen, medications, and targeted tests.

Specimen and method checks

An underfilled tube leaves excess citrate for the plasma volume and may prolong times. A hematocrit above 55% also reduces the plasma volume, so adjust the citrate volume as the procedure directs. Check for clots, heparin from a line draw, delays, and optical interference.

Anticoagulant effects depend on drug, concentration, and method. Normal times cannot exclude a direct oral anticoagulant.

What a mixing study shows

Equal volumes of patient and normal plasma supply missing factors. If the time corrects by the method's criteria, deficiency is more likely. Failure to correct suggests an inhibitor or drug. Some inhibitors become apparent only after incubation.

Mixing also dilutes inhibitors, so a weak inhibitor may be missed. Anticoagulant drugs can mimic an inhibitor pattern.

Bleeding with normal PT/APTT: investigate von Willebrand disease, platelet dysfunction, mild factor deficiencies, or factor XIII deficiency.

Hematology04 / 10PT and APTT patternsScreening patterns, specimen checks, and mixing studies

Hematology, quick reference 7 of 10
RBC morphology
Eight shape findings on a stained peripheral blood film
Assess red blood cell (RBC) shape where cells lie singly or just touch and normal central pallor remains visible. Thick areas distort shape and obscure pallor. Normal pallor occupies about one third of a cell's diameter.
May-Grünwald Giemsa-stained blood films.
Echinocyte
Short, evenly spaced projections. Often an artifact. Also seen in uremia. Acanthocytes have irregular projections.
Acanthocyte
Uneven projections of varied length. Severe liver disease and lipid disorders. Compare with regular echinocytes.
Spherocyte
Dense, no central pallor (single arrow). Immune hemolysis and hereditary spherocytosis. Thick areas hide normal pallor.
Elliptocyte
Elongated ovals (paired arrows). Hereditary elliptocytosis and iron deficiency. Large ovals suggest megaloblastic change.
Target cell
Stained center, pale ring, outer rim. Thalassemia, liver disease, and hemoglobin variants. Uneven distribution across the film suggests an artifact.
Stomatocyte
Slit-like central pallor. Hereditary stomatocytosis and liver disease. Slow drying can mimic this.
Teardrop cell
One tapered end (dacrocyte). Marrow fibrosis, marrow infiltration, and megaloblastic anemia. Artifact tails often point the same way.
Schistocyte
Angular or helmet-shaped fragment. Microangiopathic or mechanical damage. Follow counting and urgent-review policy.
Assess schistocytes by their number and the other film findings, alongside the blood count and hemolysis studies.
Image credits.
https://latticemls.org/guides/red-cell-shapes/ · Sources checked September 5, 2026 · v62badb80
© Berberian Labs LLC · CC BY-NC-SA 4.0
Hematology07 / 10RBC morphologyEight shape findings on a stained peripheral blood film

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Hematology

Steps

More skills in this part

Hematology

Systematic microscopic film examination

Iron study patterns

Typical adult patterns

Why inflammation changes the panel

When results do not agree

PT and APTT patterns

Patterns and possible explanations

Specimen and method checks

What a mixing study shows

RBC morphology

Echinocyte

Acanthocyte

Spherocyte

Elliptocyte

Target cell

Stomatocyte

Teardrop cell

Schistocyte