FUNCTIONAL DESCRIPTION
9-2 Sysmex KX-21 Operator’s Manual -- Revised October 1998
2. DETECTION PRINCIPLE
This instrument performs blood cell count by DC detection method.
2.1 DC Detection Method
Blood sample is aspirated, measured to a predetermined volume, diluted at the specified
ratio, then fed into each transducer. The transducer chamber has a minute hole called the
aperture. On both side of the aperture, there are the electrodes between which flows direct
current. Blood cells suspended in the diluted sample pass through the aperture, causing
direct current resistance to change between the electrodes. As direct current resistance
changes, the blood cell size is detected as electric pulses.
Blood cell count is calculated by counting the pulses, and a histogram of blood cell sizes is
plotted by determining the pulse sizes. Also, analyzing a histogram makes it possible to
obtain various analysis data.
Internal Electrode -
External Electrode +
Blood Cell Suspension
Aperture
DC Supply
Resistance
DC
Transducer Chamber
Figure 9-2-1: DC Detection Method
2.2 Non-Cyanide Hemoglobin Analysis Method
To analyze hemoglobin by automated methods, the Cyanmethemoglobin method or
Oxyhemoglobin method have so far been the main stream.
Cyanmethemoglobin method was recommended as the international standard method in 1966
by ICSH (International Committee for Standardization in Haematology). This method,
however, is so low in hemoglobin conversion rate that it cannot be said an appropriate
method in the automated process in which multi-sample processing is the pre-condition. In
addition, this method uses the reagent of cyanide compound which is a poisonous substance
and requires waste processing; thus, it can hardly be called an environmentally favorable
method.
At present, this method cannot be said suitable for a fully-automated instrument which is
required to handle a large amount of waste.
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