Free ASCP MLS Exam Practice Questions Mock Test: Part 44 – Hematology Laboratory Techniques and Instrumentation

The Kleihauer-Betke test is an acid elution test used to detect and quantify fetal hemoglobin (HbF)-containing red cells in maternal blood.

• Principle: Adult hemoglobin (HbA) is eluted (washed out) by acid, but fetal hemoglobin (HbF) resists acid elution and remains in the red cells.

• When stained, fetal cells appear bright pink, while adult cells appear as pale “ghost” cells.

The hemoglobin solubility test (also called the sickle cell solubility test or dithionite solubility test) is a screening test for Hemoglobin S (HbS).

Principle:

• When hemoglobin is reduced (using a reducing agent like sodium dithionite) in a phosphate buffer,

• HbS becomes insoluble and forms a turbid, cloudy suspension,

• While normal hemoglobin (HbA) remains soluble and the solution stays clear.

Nonspecific esterase (using substrates like alpha-naphthyl acetate) is a cytochemical stain that is strongly positive in cells of the monocytic lineage, including monoblasts and promonocytes. This positivity is inhibited by sodium fluoride (NaF), which helps confirm the monocytic origin. It is a key stain for differentiating acute monocytic leukemia from acute myeloid leukemia.

Other options:

• Myeloblasts: positive for MPO and Sudan black B

• Lymphoblasts: positive for PAS

• Plasma cells: not detected by NSE

The cyanmethemoglobin method is the reference method for measuring hemoglobin. It works by converting all forms of hemoglobin (like oxyhemoglobin, deoxyhemoglobin, carboxyhemoglobin, and methemoglobin) into stable cyanmethemoglobin, which is then measured.

In automated hematology analyzers, hemoglobin concentration is directly measured, typically using a colorimetric method (like the cyanmethemoglobin method) after lysing the red blood cells. The hematocrit and RBC indices (MCV, MCH, MCHC) are calculated values derived from the directly measured RBC count and hemoglobin.

PCR (Polymerase Chain Reaction) and its related techniques (like DNA sequencing) are the most specific methods for detecting specific gene mutations (e.g., JAK2 in myeloproliferative neoplasms, BCR::ABL1 in CML). These methods directly analyze the DNA sequence to identify the exact genetic abnormality.

Other techniques:

• Flow cytometry: detects cell surface markers, not specific DNA mutations

• Cytochemistry: stains cell components (enzymes, granules), lineage identification

• Hemoglobin electrophoresis: detects hemoglobin variants, not DNA-level mutations

The Coulter principle states that cells are poor conductors of electricity. When a cell passes through an aperture in a saline solution, it displaces its own volume of electrolyte, causing a momentary change in electrical resistance (impedance). The number of pulses indicates the cell count, and the pulse height is proportional to the cell volume.

Other options:

• (b) Optical density → used for hemoglobin measurement (cyanmethemoglobin method)

• (c) Light scatter → used in flow cytometry or optical cell counters

• (d) Fluorescent dye uptake → used for cell viability or nucleic acid analysis

• Automated reticulocyte counts use fluorescent dyes (e.g., thiazole orange) that bind specifically to residual RNA in immature red blood cells.

• The analyzer detects fluorescence intensity, which correlates with reticulocyte presence and maturity.

Other options:

• (a) Light scatter: used for cell size and granularity, not specific for reticulocytes

• (c) Electrical impedance: counts total cells, cannot distinguish RNA content

• (d) Osmotic lysis: used for RBC fragility tests, not reticulocytes

Trapped plasma between red blood cells, especially in conditions like spherocytosis or sickle cell anemia where cells are less deformable, is not expelled during centrifugation. This trapped plasma is incorrectly measured as part of the red cell column, leading to a falsely elevated hematocrit.

Other options:

• (a) In vitro hemolysis: destroys RBCs → falsely low hematocrit

• (c) Short centrifugation: incomplete packing → falsely high, but mainly due to trapped plasma (so b is the direct reason)

• (d) Improperly sealed tube: sample leakage → invalid/low result

A normal WBC differential count is performed by examining a stained peripheral blood smear and classifying 100 leukocytes into their respective types (neutrophils, lymphocytes, monocytes, eosinophils, basophils).

• Manual differential: typically 100 cells are counted under oil immersion.

• If abnormal or low WBC count: sometimes 200 cells may be counted for better accuracy.

While excellent for quantitative analysis, automated analyzers have a key limitation: they cannot reliably identify and classify abnormal cell morphology, such as atypical lymphocytes, blasts, dysplastic features, or certain parasites (e.g., malaria). A manual blood smear review by a technologist is still essential when flags or clinical indications suggest abnormalities.

Other options are advantages, not limitations:

• High reproducibility → strength

• Large test menu → strength

• High throughput → strength

Flow cytometry analyzes cells in a fluid stream as they pass through a laser beam. It measures:

• Light Scatter: Forward scatter (FSC) indicates cell size, and side scatter (SSC) indicates internal complexity/granularity.

• Fluorescence: Emitted from fluorescently-tagged antibodies bound to specific cell surface or intracellular markers (e.g., CD antigens).

Other options:

• (a) Electrical resistance → principle of Coulter method

• (c) Osmotic fragility → tests RBC membrane stability

• (d) Hemoglobin concentration → measured by spectrophotometry

Cold agglutinins cause red blood cells to clump at room temperature, leading to a falsely low RBC count, high MCV, and high MCHC. Warming the sample to 37°C dissolves the agglutination, allowing the analyzer to count the cells correctly. The warmed sample should be run immediately for accurate results.

Other options:

• (a) Diluting in saline won’t correct agglutination.

• (c) Manual counting won’t fix the problem if clumping persists.

• (d) Reporting initial results would be inaccurate.

The cyanmethemoglobin method is the standard reference method for measuring hemoglobin concentration in automated hematology analyzers. It lyses red blood cells and converts all forms of hemoglobin (except sulfhemoglobin) into stable cyanmethemoglobin, which is then measured photometrically at 540 nm.

Other options:

• (b) Osmotic lysis test → used for RBC membrane fragility

• (c) ELISA → antigen/antibody testing, not Hb

• (d) Immunofluorescence → used in flow cytometry, not Hb measurement

The absolute cell count represents the actual number of a specific type of cell (e.g., neutrophils, lymphocytes) in a given volume of blood.

It is calculated using the formula:

For example:
If the total WBC count = 8,000 /µL
and neutrophils = 60%

Then,

$$\text{Absolute neutrophil count}=(60/100)\times 8000=4800/\mu L$$

Tilting the Westergren tube from the vertical position increases the sedimentation rate by altering the gravitational forces and the dynamics of rouleaux formation, leading to a falsely elevated ESR. The other options (refrigeration, microclots, and delayed testing) are more likely to cause a falsely low ESR.

Other options:

• (a) Refrigeration → slows sedimentation → falsely low ESR

• (c) Microclots → interfere with RBC settling → falsely low ESR

• (d) Delay >6 hours → RBC morphology changes → usually falsely low ESR

On a Sysmex DIFF scattergram:

• Side Scatter (Y-axis) relates to the cell’s internal complexity (granularity). Neutrophils are highly granular, so they have high side scatter.

• Fluorescence Intensity (X-axis) relates to the nucleic acid content (DNA/RNA). Mature neutrophils have a segmented nucleus with condensed chromatin, resulting in low fluorescence.

The spun microhematocrit method is a direct way to measure the Packed Cell Volume (PCV), which is the percentage of total blood volume occupied by red blood cells after centrifugation. The result is expressed as a percentage and is equivalent to the hematocrit (Hct).

Other options:

• (a) Plasma hemoglobin: measured spectrophotometrically

• (c) Total iron stores: assessed via bone marrow iron stain

• (d) Reticulocytes: counted via supravital stain or automated fluorescence

The osmotic fragility test measures the stability of red blood cell membranes by exposing them to a series of saline solutions with decreasing concentrations. Cells with abnormal membranes (like spherocytes) are more fragile and lyse at higher saline concentrations, while normal RBCs can withstand lower osmotic pressure before hemolyzing.

Other options:

• Platelet function: assessed by bleeding time, platelet aggregometry

• WBC lysis resistance: not routinely tested

• Coagulation factor activity: assessed by PT, aPTT, clotting assays

The Red Cell Distribution Width (RDW) is a measure of the variation in red blood cell volume (size). A high RDW indicates anisocytosis (a significant variation in RBC size), which is commonly seen in conditions like iron deficiency anemia.

Other parameters:

• MCH: mean hemoglobin content per RBC

• MCHC: hemoglobin concentration within RBCs

• MPV: mean platelet volume (platelet size, not RBCs)

The standard manual platelet count using a hemocytometer uses the following calculation:

Total Platelet Count/µL = (Average count per square) × (Depth Factor) × (Dilution Factor)

• Average count per square: 180 platelets (in the central squares)

• Depth Factor: 10 (the chamber depth is 0.1 mm, which is factored as 10)

• Dilution Factor: 100

The Prussian blue stain (also known as Perl’s stain) is the specific histochemical stain used to detect storage iron (hemosiderin) in the bone marrow macrophages. Iron reacts with potassium ferrocyanide in an acidic solution to form an insoluble blue pigment. This is the standard method for assessing iron stores.

Other stains:

• Wright stain → routine blood smear morphology

• Myeloperoxidase stain → enzyme in myeloid cells

• Sudan Black B → lipid components in myeloid granules

• Polychromatophilic RBCs are young red blood cells that still contain residual RNA. On a standard Wright stain, this RNA causes the cytoplasm to stain with a blue-gray hue (polychromasia).

• Supravital stains (like new methylene blue or brilliant cresyl blue) specifically stain this residual RNA, causing it to precipitate and form a blue network or granules within the cell.

• A cell that shows this blue network after supravital staining is definitively identified as a Reticulocyte.

Why the other options are incorrect:

• a) Spherocyte: A spherocyte is a sphere-shaped red cell with no central pallor, identified by its morphology, not by a supravital stain.

• b) Target cell: A target cell has a characteristic “bullseye” appearance, also identified by its morphology on a Wright stain.

• d) Sickle cell: A sickle cell has a crescent or sickle shape, identified by its morphology, often requiring a sickle cell prep (sodium metabisulfite) to induce the sickling.

The Wright-Giemsa stain is a Romanowsky-type stain. Its key components are:

• Methylene blue derivatives (e.g., azure B), which are basic dyes that stain acidic components (like nucleic acids) blue-purple.

• Eosin, which is an acidic dye that stains basic components (like hemoglobin and cationic proteins) pink-orange.

While not entirely specific, the PAS stain is the most useful cytochemical stain for identifying lymphoblasts, particularly in acute lymphoblastic leukemia (ALL). Lymphoblasts often show a characteristic “block-like” or coarse granular positivity with PAS, whereas they are typically negative for MPO and Sudan Black B (which are markers of myeloid lineage).

Other options:

• MPO and Sudan black B: positive in myeloblasts

• Esterase stain: identifies monocytes or monocytic lineage, not lymphoblasts

Platelet clumping caused by EDTA-dependent antibodies leads to platelets aggregating in vitro. These clumps are too large to be counted as individual platelets by automated analyzers, resulting in a falsely low platelet count, a condition known as pseudothrombocytopenia.

Other options:

• (b) Thrombocytosis → falsely high platelet count (opposite effect)

• (c) Leukopenia → not affected by platelet clumping

• (d) Polycythemia → increased RBC mass, unrelated

The main advantage of automation in hematology is the ability to process a large number of samples quickly while providing highly accurate and reproducible results for parameters like CBCs and differentials, which improves laboratory efficiency and patient care.

Other options:

• (a) Reduces need for anticoagulants: false, anticoagulants are still required

• (c) Eliminates need for staining: false, staining may still be required for manual differentials or morphology

• (d) Removes operator oversight completely: false, operator review is still needed for flagged or abnormal results

• Heinz bodies are precipitates of denatured hemoglobin attached to the inner red cell membrane.

• They are not visible on routine Wright-stained smears.

• They are best seen using supravital stains, especially Brilliant cresyl blue or Crystal violet.

Other stains:

• (a) Wright stain: does not show Heinz bodies clearly.

• (c) Prussian blue: detects iron (hemosiderin).

• (d) New methylene blue: shows reticulocytes (RNA), not Heinz bodies.

External quality assurance (EQA), or proficiency testing, involves testing unknown samples provided by an external agency and comparing your laboratory’s results with those of other laboratories or a reference method. This independent assessment helps ensure the accuracy and reliability of a lab’s testing procedures across different institutions.

Other options:

• (a) Daily analyzer maintenance: part of routine operations, not EQA

• (c) Checking patient identification: part of lab workflow, not EQA

• (d) Using duplicate samples only: internal check, not external comparison

The Westergren method is the standard manual technique for measuring the Erythrocyte Sedimentation Rate (ESR). It involves filling a Westergren pipette with anticoagulated blood and measuring the distance the red blood cells fall in one hour. It is the reference method endorsed by organizations like the ICSH.

Other options:

• (a) Cyanmethemoglobin → measures hemoglobin concentration

• (c) Schilling test → measures vitamin B₁₂ absorption

• (d) Osmotic fragility → assesses RBC membrane stability

A supravital stain is applied to living cells (or a fresh, unfixed blood sample) to stain for specific components. For reticulocytes, the target is the residual ribosomal RNA (rRNA).

• New methylene blue is a supravital stain that specifically precipitates and stains the rRNA within reticulocytes, making them easily identifiable under a microscope by their characteristic blue reticulum or network.

Why the other options are incorrect:

• a) Wright stain & b) Giemsa stain: These are Romanowsky-type stains. They are applied to fixed blood smears and are used for the general morphological assessment of all blood cells. While they can show polychromatophilic red cells (which are reticulocytes), they do not specifically stain the reticulum and are not classified as supravital stains.

• d) Prussian blue: This is a histochemical stain used to detect iron stores (hemosiderin) in tissues, such as in bone marrow aspirates. It is not used for staining reticulocytes.

Use the NRBC correction formula:

Corrected WBC=Reported WBC×100NRBCs+100\text{Corrected WBC}=\frac{\text{Reported WBC} \times 100}{\text{NRBCs} + 100}Corrected WBC=NRBCs+100Reported WBC×100​

Reported WBC = 10.0×103/μL=10,000/μL10.0\times10^3/\mu L = 10{,}000/\mu L10.0×103/μL=10,000/μL
NRBCs = 50 per 100 WBCs

Compute step-by-step:

• $10,000\times 100=1,000,000$

• $50+100=150$

• 1,000,000÷150=6,666.6‾1{,}000{,}000 \div 150 = 6{,}666.\overline{6}1,000,000÷150=6,666.6

Round to whole cells: 6,667/µL.

Why the other options are incorrect:

• a) 5,000/µL: This is roughly half the reported count, which would be the case if the number of NRBCs equaled the number of WBCs (100 NRBCs/100 WBCs).

• c) 8,000/µL: This is a less drastic correction that doesn’t match the calculated result.

• d) 15,000/µL: This would be an even higher number, which is incorrect as the presence of NRBCs falsely elevates the initial count.

Sysmex hematology analyzers are known for using the technology called Multi-Angle Polarized Scatter Separation (MAPSS) for their white blood cell differential count. This method uses different angles of laser light scatter to identify and classify white blood cells.

• Dilution = 1:20

• Number of cells counted = 50

• Area counted = 4 corner squares of the hemocytometer

• Each large WBC square = 1 mm² area

• Depth of chamber = 0.1 mm

Step 1: Determine the volume counted

Each large square volume =

Area×Depth=1 mm2×0.1 mm=0.1 mm3\text{Area} \times \text{Depth} = 1 \, \text{mm}^2 \times 0.1 \, \text{mm} = 0.1 \, \text{mm}^3Area×Depth=1mm2×0.1mm=0.1mm3

For 4 squares:

4×0.1=0.4 mm34 \times 0.1 = 0.4 \, \text{mm}^34×0.1=0.4mm3

Step 2: Calculate cells per mm³ (or µL)

Cells per mm3=Number of cells counted×Dilution factorVolume counted\text{Cells per mm}^3 = \frac{\text{Number of cells counted} \times \text{Dilution factor}}{\text{Volume counted}}Cells per mm3=Volume countedNumber of cells counted×Dilution factor​ =50×200.4=10000.4=2500= \frac{50 \times 20}{0.4} = \frac{1000}{0.4} = 2500=0.450×20​=0.41000​=2500 =2,500 WBCs per mm3 (or per µL)= 2,500 \, \text{WBCs per mm}^3 \, (\text{or per µL})=2,500WBCs per mm3(or per µL)

• In polycythemia vera, the hematocrit is markedly elevated, meaning there is less plasma volume in the blood sample.

• When the standard amount of sodium citrate anticoagulant is used, the plasma-to-anticoagulant ratio becomes unbalanced, resulting in excess citrate relative to plasma.

• This excess chelates more calcium during coagulation testing, leading to falsely prolonged PT and aPTT results.

Hemoglobin electrophoresis separates hemoglobin variants based on charge differences at different pH levels.

Other options:

• Alkaline only: may miss some variants

• Acid only: insufficient for common hemoglobins

• Neutral: rarely used for routine electrophoresis

Commercially prepared whole blood controls are used daily to monitor the precision and accuracy of hematology analyzers. These controls have known target values for all CBC parameters (RBC, WBC, Hgb, Hct, platelets, indices) and are run to ensure the instrument is operating within established performance limits.

Other options:

• Normal saline or distilled water: do not contain cells → cannot test analyzer function

• EDTA plasma only: lacks cellular components → not sufficient for CBC quality control

The Mean Corpuscular Volume (MCV) is the average volume of a red blood cell. It is calculated by dividing the hematocrit (Hct) by the red blood cell count (RBC), and then multiplying by 10 to convert the units from femtoliters (fL) to the conventional reporting unit.

EDTA (Ethylenediaminetetraacetic acid) is the anticoagulant of choice for routine hematology testing, including CBCs. It perfectly preserves cellular morphology and prevents clotting by chelating calcium, without interfering with the cellular analysis or staining characteristics of blood cells.

Other anticoagulants:

• (a) Sodium citrate: used for coagulation studies (PT, aPTT).

• (b) Heparin: used for some chemistry and cytogenetic tests; causes WBC clumping in CBC.

• (d) Potassium oxalate: used with sodium fluoride for glucose testing, not hematology.

Internal quality control (IQC) involves the daily use of control materials with known values to verify that an analytical process (like running a CBC on a hematology analyzer) is producing accurate (true) and precise (reproducible) results before patient samples are reported.

Other options:

• (a) Correct test ordering: part of laboratory management, not IQC

• (c) Elimination of human error: IQC reduces errors but cannot eliminate them entirely

• (d) Calibration once per year only: calibration frequency is separate from daily IQC

Both Myeloperoxidase (MPO) and Sudan black B (SBB) are cytochemical stains used to identify cells of the myeloid lineage, including myeloblasts. They are considered the most specific and reliable stains for this purpose, with SBB often being slightly more sensitive. A positive reaction with either stain confirms myeloid differentiation.

In the Siemens Advia hematology analyzer, the Peroxidase (Perox) channel differentiates white blood cells based on:

• Peroxidase activity (x-axis) → indicates enzyme content

• Light scatter (y-axis) → indicates cell size and internal complexity

A falsely high MCHC is typically caused by errors that increase the hemoglobin measurement or decrease the red cell volume (MCV) calculation.

• Lipemia: Increases turbidity, falsely elevating the hemoglobin measurement.

• Cold agglutinins: Cause red cells to clump, leading to a falsely low RBC count and MCV, which artificially inflates the MCHC.

• Spherocytosis: The red cells have a smaller volume (low MCV) but normal hemoglobin content, leading to a genuinely high MCHC.

• High Reticulocyte Count: Reticulocytes are larger, which would typically lower the MCHC, not raise it. It does not cause a false elevation.

Excess EDTA draws water out of red blood cells due to osmotic effects, causing them to shrink (crenate) and lose their normal biconcave shape. This can make them appear as spherocytes or echinocytes (burr cells) on a blood smear, leading to altered red cell indices.

Other options:

• (a) Hypochromic: due to low hemoglobin, not excess EDTA

• (c) Rouleaux formation: due to increased plasma proteins (e.g., multiple myeloma)

• (d) Macrocytic: cells would appear larger, opposite of EDTA effect

A reticulocyte count requires a supravital stain, such as new methylene blue or brilliant cresyl blue. These stains are applied to living, unfixed red blood cells and precipitate the residual RNA in reticulocytes, making it visible as a blue network or granules. This allows for the identification and counting of these immature red cells.

Other stains:

• (a) Wright–Giemsa: routine blood film (does not show reticulum)

• (c) Prussian blue: iron stores

• (d) Sudan black: lipids in myeloid cells

The Kleihauer–Betke test is an acid elution technique used to detect red blood cells containing fetal hemoglobin (HbF). HbF is resistant to acid elution and remains pink, while adult hemoglobin (HbA) is eluted, leaving “ghost” cells. This test is primarily used to detect and quantify fetomaternal hemorrhage.

Other options:

• Heinz bodies: detected by supravital stain

• Iron granules: detected by Prussian blue stain

• DNA remnants: detected by Howell–Jolly bodies

The Red Cell Distribution Width (RDW) is a numerical measure of the variation in the size of red blood cells (RBCs). A high RDW indicates a high degree of anisocytosis (variation in cell size), which is seen in conditions like iron deficiency anemia or vitamin B12 deficiency.

• CD5 is a T-cell–associated antigen that is normally expressed on mature T lymphocytes.

• It can also be found aberrantly on a subset of B cells, especially in chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL) — which helps in their immunophenotypic identification.

So, under normal conditions → CD5 = mature T cells.

The principle of electrical impedance (also known as the Coulter principle) is based on cells being poor conductors of electricity compared to the liquid they are suspended in.

• The primary anticoagulant for routine hematology testing (CBC, blood smear, reticulocyte count) is EDTA (ethylenediaminetetraacetic acid), in either the dipotassium (K₂EDTA) or tripotassium (K₃EDTA) form.

• Mechanism: EDTA chelates calcium (Ca²⁺), preventing clotting while preserving cellular morphology and blood integrity for several hours.

Other options:

• (a) Sodium citrate: used for coagulation studies (PT, aPTT).

• (c) Heparin: used in plasma chemistry and cytogenetics, not CBC.

• (d) Oxalate: used with fluoride for glucose testing, not hematology.

A flag for “immature granulocytes” (IG) is a critical alert from the analyzer that cells normally not present in significant numbers in peripheral blood (such as promyelocytes, myelocytes, and metamyelocytes) have been detected. The presence of these cells can be clinically significant, indicating conditions like infection, inflammation, or a bone marrow disorder (e.g., leukemia).

Why the other options are incorrect:

• a) Report the results as-is: This is dangerous and violates laboratory standards. Reporting unflagged automated results is acceptable, but any critical flag must be investigated.

• c) Warm the specimen to 37°C and rerun: This is a procedure used for a cold agglutinin flag, where RBCs clump in the cold, not for an IG flag.

• d) Request a new sample: There is no indication that the sample is compromised (e.g., clotted, hemolyzed). The IG flag is likely a true biological finding, not an artifact of poor collection. A new sample would likely show the same flag.

• MPV represents the average size of platelets in a blood sample.

• It is directly measured by automated hematology analyzers using electrical impedance or optical methods.

Other platelet parameters:

• PDW (Platelet Distribution Width): variation in platelet size

• MCHC: mean hemoglobin concentration in RBCs

• RDW: variation in RBC size

Auer rods are needle-shaped cytoplasmic inclusions composed of fused primary granules. They are a morphologic hallmark of myeloid lineage and are most commonly and readily identified during the routine examination of a blood smear or bone marrow aspirate stained with a Romanowsky-type stain, such as Wright’s stain or Wright-Giemsa.

Side scatter (SSC) is the measurement of light scattered at approximately 90 degrees. This occurs when light hits internal structures within the cell. Therefore, SSC is directly proportional to the cell’s internal complexity or granularity. Cells with more granules (e.g., neutrophils) have high SSC, while cells with simple cytoplasm (e.g., lymphocytes) have low SSC.

Other options:

• (a) Cell volume → forward scatter

• (c) Hemoglobin concentration → measured spectrophotometrically, not by scatter

• (d) Membrane charge → not assessed in flow cytometry

• Terminal deoxynucleotidyl transferase (TdT) is a nuclear enzyme expressed in immature lymphoid cells — specifically pre–B and pre–T lymphoblasts.

• It is not present in mature lymphocytes or myeloid cells.

The Mean Corpuscular Hemoglobin (MCH) is the average amount of hemoglobin per red blood cell. It is calculated using the formula:

MCH (pg) = (Hemoglobin (g/dL) × 10) / RBC count (×10¹²/L)

This gives the result in picograms (pg) per cell.

Other RBC indices:

• MCV = (Hct × 10) / RBC → average red cell size

• MCHC = (Hgb × 100) / Hct → average concentration of hemoglobin in RBCs

• RDW → variation in RBC size (anisocytosis)