Hematology Lecture Auto Blood Analysis

Electrical Impedance

The measurement of charges in electrical resistance produced by cells as they traverse a small aperture; cells are suspended in conductive diluent then pulled through aperture in a tube.

Electrical Impedance Histogram

Determination of RBC count and MCV; allows calculation of Hct, MCH, and MCHC

2-20fL

The amount of platelets the histogram can separate

>36 fL

The amount of RBCs the histogram can separate

35-90fL

The amount of lymphs the histogram can separate

90-160fL

The amount of mononuclear cells the histogram can separate

160-450fL

The amount of granulocytes the histogram can separate

Protein Buildup

Lower cell counts and falsely elevated cell volumes in electrical impedance

Coincident passage of more than one cell

Falsely increased cell volumes and decreased cell counts

Flow Cytometers Light Scattering

Results based off process of absorption, diffraction, refraction, and reflection

Orthogonal Light

Scatter/side scatters allows furthers characterizing of cells giving differentiation of 5 types of WBCs based on volume and internal features

Cythochemical and fluorescent staining

Distinguishes segs, eos, and monos that are peroxidase positive from lymphs, basos, and PLTS that are peroxidase negative; dyes bind to DNA and RNA in WBCs, NRBCs, PLTs, and retics for identification

Cyanmetheomoglobin

The reference method for measuring Hgb

Beckman-Coulter, Sysmex, Abbott, and Siemens Healthineers

The multiple analyzer manufacturers

Hydraulics

The aspirating unit, dispensers, diluters, mixing chambers, aperture baths or flow cells or both, and hemoglobinometer

Pneumatics

Generates vacuums and pressures required for operating the valves and moving specimen through the hydraulics system

Electrical

Controls operational sequences of system and includes electronic analyzers and computing circuitry for data processing as well as a data display

Beckman Coulter

UniCel DxH 900 uses spectrophotometry, impedance, RF conductivity, & multiangle laser light scatter

Sysmex

XN-3100 system uses spectrophotometry, DC detection, & fluorescence flow cytometry with multiangle scatter & fluorescence detection

Abbott

CELL-DYN Sapphire uses spectrophotometry, impedance, & multiangle laser light scatter with fluorescence detection

Siemens Healthineers

ADVIA 2120/2020i uses spectrophotometry, light scatter, & cytochemistry

International Council for Standardization in Hematology (ICSH)

Published the guidelines for evaluation of blood cell analyzers

Limitations of Impedance Technology

Analyzer’s inability to reliably distinguish cells from other particles or cell fragments

Errors in Hemoglobin Determination

Due to spectrophotometric measurement, turbidity of specimen after RBC lysing the Hgb can be falsely increased

Errors in Retic Counting

Falesely increased retic counts can be due to RNA stain reacting with RBC inclusions, malarial parasites, giant PLT, and Hgb S & C

Specimen Integrity & Stability

Specimens should be properly collected, stability of CBC parameters is about 24 hours at RT & 48 hours refrigerated