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Automated Techniques by ewghwehws


									Automated Techniques

    CLS 541-Advanced Medical
         M. sc. Program
A variety of automated instruments for performing
  blood counts have been developed and are now
  widespread use.
Semiautomated instruments often measure a small
  number of components e. g WBC and Hb.
Fully automated multi-channel instruments usually
  measure 8-20 components, including some new
  variables which have no equivalent in manual
High level of precision in automated instruments.
 If use quality control and good calibrated
  the results will be very accurate.
 The most recently developed blood cell
  counters , have automated procedures for
  sample recognition e. g by bar-coding.
 In large laboratories (80-100 samples per
  hour) require fully automated blood
  counters capable of the rapid production
  of accurate and precise blood counts.
 Choice of an instrument for an individual
  laboratory should take running coast,
  including maintenance and reagents; size
  of instrument requirement of service such
  water, compressed air, draining and an
  electricity supply with stable voltage.
 UK National health service medical devices
          Hb concentration

 Most   automated counters measure
  Hb by a modification of the manual
  haemoglobincyanid method (HICN).
 Modification include alteration in the
  concentration of reagents and in the
  temperature and PH of the reaction.
 Measure the absorbance.
        Red blood cell count

 Can    be counted in system based
    on either:
 1- aperture impedance
 2- light scatter technology.
 A large numbers of cells can be counted
  rapidly, there is a high level of precision.
         aperture impedance
 Impedance counting depends on the fact that
  red cells are poor conductors of electricity
  whereas certain diluents are good conductors;
  this difference forms the basic of the counting
  systems used in many instruments.
 Blood highly diluted in buffered electrolyte
  solution. The flow rate of this diluted sample is
  controlled. This result is measured volume of the
  sample passing through an aperture tube of
  specific dimensions.
            Light scattering
 Red cells and other blood cells may be counted
  be means of electro-optical detectors.
 A diluted cell suspension flows through an
  aperture so that the cells pass, in single file, in
  front of a light source; light is scattered by cells
  passing through the light beam. Scattered light
  is detected by a photomultiplier or photodiode
  which converts into electrical impulses which a
  accumulated and counted.
   The a mount of light scattered is
    proportional to the surface area and
    therefore the volume of the cell so that
    the height of the electrical pulses can be
    used to estimate the cell volume.
Haematocrite           and      red      cell
 The term ‘haematocrite’(Hct) rather than
  PCV should be used for the automated
 The red cell indices included: MCV, MCH
  and MCHC; more recently; red cell
  distribution width (RDW).
 All these values will automatic calculation.
          Total WBC count
 The total WBC is determined in whole
  blood in which red cells have been lytic.
 Can be counted in system based on either
  aperture impedance or light scatter
 The precision of the automatic count was
  no better than that of manual count.
 A three part differential count assigns cells
  to categories usually designed: (a)
  ‘granulocytes’    or    ‘large   cell’;   (b)
  ‘lymphocyte’     or    small    cells;   and
  ‘monocytes’ or ‘middle cells’.
 Both impedance counter or light scattering
  instrument are capable of producing
  three-part differential counts from single
  channel; the categorization is based on
  the different volume of various types of
  the cell following partial lysis and
  cytoplasmic shrinkage.
Platelet count and other platelet
 Platelet can be counted in whole blood
  using the same techniques for counting
  red cells.
 Mean platelet volume (MPV) which vary
  inversely with platelet count in normal
 Platelet distribution width (PDW) which is
  a measure of platelet anisocytosis and

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