Automated Processes in Hematology

HEMATOLOGY AUTOMATION

• Automation has improved precision and accuracy of patient results.
• Reduced reliance on manual techniques as processes become more automated.
• Example advancements:
  • Blood smears have evolved: three-part differential → five-part differential → seven-part differential.
  • Automated reticulocyte counts and new indices enhance diagnostic efficiency.
  • Automation in counting body fluids contributes to timely disease management.

HISTOGRAMS

• Histograms are customizable graphic representations showing cell frequencies versus size.
• Data is collected and plotted in a volume/frequency distribution format:
  • Y-axis: relative number of cells
  • X-axis: cell size or volume (measured in femtoliters, fL)
• Histograms are useful for analyzing:
  • Erythrocyte (RBC) populations
  • Leukocyte (WBC) populations
  • Platelet populations

ELECTRICAL IMPEDANCE

• Cells are sized and counted through changes in electrical resistance when they pass through a small aperture.
• Utilized on Sysmex or cell analyzers for RBC and platelet counting.
• Blood sample diluted in saline to improve conductivity:
  • Cells are drawn through an aperture via vacuum.
  • Two electrodes establish an electrical current.
• Low-frequency alternating current is applied, resulting in:
  • Voltage changes generating pulses corresponding to cell counts.
• Malfunctions in aperture can affect counting accuracy.

HYDRODYNAMIC FOCUSING

• Technique to ensure RBCs aren’t counted twice:
  • Narrows cell stream to single file to enhance accuracy.
  • Directs cells past detection aperture, preventing recirculation.

CELL ANALYSIS PARAMETERS

• Understanding key parameters from hematology profiles:
  • WBC/BASO: White blood cell counts.
  • RBC: Red blood cell counts.
  • HGB: Hemoglobin levels (measured in mmol/L).
  • HCT: Hematocrit values (measured in L/L).
  • MCV: Mean corpuscular volume (average size of RBC in fL).
  • MCH, MCHC, PLT: Various indices of RBC and platelet characteristics.

SCATTERGRAMS/SCATTERPLOTS

• Scatterplots depict multiple measurable cell characteristics:
  • Use light scatter for analyzing cell populations.
  • Help identify population abnormalities and specific subpopulations including lymphocytes, granulocytes, and monocytes.

FLOW CYTOMETRY

• Utilizes laser light to analyze cell characteristics:
  • Measures light scatter to evaluate:
  • Cell size
  • Cytoplasmic granularity
  • Nuclear complexity
• Produces scattergrams to cluster cell types:
  • Distinguishes granulocytes, monocytes, and lymphocytes.

HEMOGLOBIN ASSESSMENT

• Hemoglobin concentrations measured using spectrophotometry:
  • Primarily through the cyanmethemoglobin method.
  • Modern analyzers favor non-cyanide methods for safety.

COAGULATION ANALYZERS

• Different methodologies employed in clot detection:
  • Mechanical End Point Detection: Utilizes metal electrodes to detect fibrin formation through changes in electrical conductivity.
  • Electromagnetic Detection: Measures viscosity changes during clot formation using oscillation of a metal ball.
  • Photometric Detection: Based on optical density changes as fibrinogen converts to fibrin, often using turbidimetric analysis.
  • Chromogenic and Immunologic Detection: Measure enzymatic activity or antigen levels using specific substrates and antibodies.
  • Example: Anti-Xa test for heparin therapy monitoring using chromogenic methods.