Hematology Laboratory Principles and Methods Flashcards

Flashcards covering hematology laboratory concepts, including cell counting principles, automation, hematocrit and hemoglobin determination, laboratory orientation, and manual hemacytometer counts.

What are the three main physical systems present in most automated hematology analyzers?

The three main systems are Hydraulics (fluid movement and diluent handling), Pneumatics (vacuums and pressures for valves and sample transport), and Electrical Systems (data processing circuits).

What basic cell counting principle measures direct current electrical resistance as nonconductive cells pass through an aperture?

Electrical Impedance, also known as the Coulter Principle.

In electrical impedance, how do voltage pulse count and pulse amplitude relate to cellular characteristics?

The number of voltage pulses is proportional to the number of cells, and the amplitude of each pulse is proportional to the cell size.

In optical scatter methods, what specific cell properties are measured by forward angle and side angle light scatter?

Forward angle light scatter measures cell size, while side angle (orthogonal) light scatter measures internal cellular complexity, granularity, and lobularity.

What light source is most commonly used in flow cytometers due to its intensity, stability, and monochromatism?

Helium-neon laser.

What are the reference cell size thresholds for platelets, erythrocytes, and leukocytes on automated cell histograms?

Platelets are measured between $2-20\,\text{fL}$, erythrocytes are measured at $>36\,\text{fL}$, and leukocytes are measured between $35-450\,\text{fL}$.

What do the histogram flags R1, R2, R3, and R4 represent on an abnormal automated WBC histogram?

R1 ($<35\,\text{fL}$) indicates nRBCs or giant/clumped platelets; R2 (overlap at $90\,\text{fL}$) indicates reactive lymphocytes or blasts; R3 (overlap at $160\,\text{fL}$) indicates bands, immature neutrophils, eosinophils, or basophils; and R4 ($>450\,\text{fL}$) indicates high granulocytes.

How do cluster locations on a WBC optical scattergram distinguish lymphocytes, monocytes, neutrophils, and eosinophils?

Lymphocytes appear in the lower left (blue: low FSC, low SSC), monocytes in the middle (green: medium FSC, moderate SSC), neutrophils in the upper region (red: high FSC, high SSC), and eosinophils in the lower right (orange: high FSC, moderate SSC).

What is the most common instrumental cause of a positive error during cell counting on an automated analyzer?

Aperture plugs.

How do cold agglutinins interfere with automated CBC results, and what is the proper corrective action?

Cold agglutinins falsely decrease RBC count and hematocrit while falsely increasing MCV and MCHC; the corrective action is to warm the specimen to $37^\circ\text{C}$ and rerun.

What are the equations that define the Rule of Three in hematology QA/QC?

$\text{RBC} \times 3 = \text{Hb}$, $\text{RBC} \times 9 = \text{Hct}$, and $\text{Hb} \times 3 = \text{Hct}$.

What four layers are formed when anticoagulated whole blood is centrifuged for hematocrit determination?

From top to bottom: Fatty layer, Plasma, Buffy coat, and Packed red cells.

What are the dimensions and color coding for microhematocrit capillary tubes?

Microhematocrit tubes are $75\,\text{mm}$ long with a $1\,\text{mm}$ bore holding $0.05\,\text{mL}$ of blood. Red band tubes contain heparin for plain capillary blood; blue band tubes are plain for anticoagulated blood.

What are the operational specifications for a microhematocrit centrifuge?

The centrifuge must have a radius $>8.0\,\text{cm}$, reach maximum speed within $30\,\text{seconds}$, and maintain a relative centrifugal force of $10,000-15,000 \times g$ for 5 minutes without exceeding $45^\circ\text{C}$.

How are the left and right graduation lines on a Wintrobe tube interpreted?

The left side (red numbers) measures ESR from $0$ to $10\,\text{cm}$ (top to bottom); the right side (white numbers) measures Hematocrit from $10\,\text{cm}$ to $0$ (top to bottom).

What are the adult reference ranges for hematocrit in conventional and SI units?

Adult women: $37\%-43\%$ ($0.37-0.43$ volume fraction); Adult men: $40\%-50\%$ ($0.40-0.50$ volume fraction).

What are the critical values for hematocrit across any age group?

$\le 0.21$ ($\le 21\%$) or $\ge 0.65$ ($\ge 65\%$).

What reaction principle forms the basis of the Sahli method for hemoglobin estimation?

Blood is mixed with $0.1\,\text{N HCl}$ to convert hemoglobin into acid hematin, which produces a brown color that is matched against a reference glass standard.

What are the key chemical constituents of Drabkin's reagent and their functions in the cyanmethemoglobin method?

Potassium ferricyanide converts ferrous iron ($Fe^{2+}$) to ferric iron ($Fe^{3+}$) to form methemoglobin; Potassium cyanide converts methemoglobin to cyanmethemoglobin ($HiCN$); and Dihydrogen potassium phosphate reduces reaction time from $10-15\,\text{minutes}$ to $3\,\text{minutes}$.

Which form of hemoglobin is NOT measured by the cyanmethemoglobin method?

Sulfhemoglobin.

What blood color alterations are associated with methemoglobin, carboxyhemoglobin, and sulfhemoglobin?

Methemoglobin produces a chocolate brown color, carboxyhemoglobin produces a cherry red color, and sulfhemoglobin produces a mauve lavender color.

What equation calculates the hemoglobin concentration of a reference solution in $\text{g/L}$ during spectrophotometer calibration?

$\text{Hb value of Reference Solution (g/L)} = \text{Concentration in mg/100 mL} \times 2.5$.

What are the adult reference ranges and critical values for hemoglobin concentration?

Adult women: $12.0-16.0\,\text{g/dL}$ ($120-160\,\text{g/L}$); Adult men: $13.0-18.0\,\text{g/dL}$ ($130-180\,\text{g/L}$). Critical values are $\le 7.0\,\text{g/dL}$ ($\le 70\,\text{g/L}$) or $\ge 20.0\,\text{g/dL}$ ($\ge 200\,\text{g/L}$).

What is the weight distribution between lecture and laboratory in MLS 3102, and what is the absence policy for dropping a student?

Lecture accounts for $60\%$ and Laboratory accounts for $40\%$ of the course grade. A student is dropped if absent for $20\%$ or more of total synchronous sessions.

What are the dimensions and total volume of an Improved Neubauer counting chamber?

Total grid area is $3\,\text{mm} \times 3\,\text{mm} = 9\,\text{mm}^2$, depth is $0.1\,\text{mm}$, and total volume is $0.9\,\text{mm}^3$.

Which specialized hemacytometers are used for manual eosinophil counts due to their larger total volumes?

Speirs-Levy ($2.0\,\text{mm}^3$ volume) and Fuchs-Rosenthal ($3.2\,\text{mm}^3$ volume) counting chambers.

How do Thoma WBC and RBC pipettes differ in physical markings, bulb beads, and dilution ranges?

The WBC pipette has a white bead, markings $0.5$, $1$, $11$, and a $1:10-1:100$ dilution range. The RBC pipette has a red bead, markings $0.5$, $1$, $101$, and a $1:100-1:1,000$ dilution range.

What reagents can be used as diluting fluids for manual WBC counting?

$1\%$ ammonium oxalate, $2-3\%$ glacial acetic acid with gentian violet, $1\%$ hydrochloric acid, or Turk's solution (glacial acetic acid and methyl violet).

What is the mathematical formula for calculating a corrected WBC count in the presence of nucleated RBCs?

$\text{True leukocyte count} = \frac{\text{Total count} \times 100}{100 + \text{No. of nRBCs}}$ (performed when $\ge 5\,\text{nRBCs}$ per $100\,\text{WBCs}$ are observed).

What are the standard adult reference ranges for manual total WBC and RBC counts in SI units?

Adult WBC count is $4.0-10.0 \times 10^9/\text{L}$. Adult RBC count is $4.0-5.4 \times 10^{12}/\text{L}$ for women and $4.5-6.2 \times 10^{12}/\text{L}$ for men.