Hematology Analyzer

Overview

A hematology analyzer produces the complete blood count, the most-ordered test in medicine: how many red cells, white cells and platelets are in a sample, how big they are, and what fraction of the white cells are each subtype. It draws a tiny volume of anticoagulated blood, prepares several precisely diluted aliquots, and counts cells one at a time as they pass through a sensing zone, turning a drop of blood into a screen of numbers and histograms in under a minute.

The Sampling System system pierces the tube and uses a Syringe Metering Pump to meter blood and diluent into the Mixing Chambers chambers, where the Reagent & Fluidics System adds diluent to one aliquot and a lysing reagent to another. Prepared aliquots are drawn through the Detection System system, which counts and sizes cells, while the Control Electronics electronics tally pulses into histograms shown on the Display Panel. Spent fluid goes to the Waste System container.

How it works

Counting uses two complementary physics. The impedance method sends a current across the Impedance Aperture, a tiny orifice; each cell that passes briefly raises the resistance, and the size of that pulse is proportional to the cell's volume, perfect for the huge populations of red cells and platelets. For the white-cell differential, the analyzer hydrodynamically focuses cells single-file through the Optical Flow Cell, illuminates each one with a Laser Diode, and reads forward and side scatter on its Scatter Photodiode detectors. Forward scatter reports size and side scatter reports internal granularity, so neutrophils, lymphocytes, monocytes, eosinophils and basophils separate into distinct clusters.

Sample preparation makes the counting honest. The Reagent & Fluidics System dilutes the red-cell aliquot enough that cells cross the aperture one at a time, while the lyse reagent in the WBC/Lyse Chamber strips red cells away so white cells can be counted cleanly and the released hemoglobin measured photometrically. Hemoglobin concentration, cell counts and the measured size distributions feed the derived indices, hematocrit, mean cell volume, and the rest. Between samples the Waste System system drains the chambers and the probe is washed, so one patient's cells never contaminate the next count.