Introduction to technology utilised in the clinical laboratory

1. Automated Blood cell analyzers
the basics
JG Nel
Department of Haematology

2. • (picture of the road ahead)

3. • (rearview mirror)

4. • (microscope)

6. Wallace and Joseph Coulter
• (Wallace and Joseph Coulter)

7. The Coulter model A

10. The Red cell count
• (red cells)

11. Aperture impedance counting

12. Light scattering

13. Factors influencing the reliability of
automated counts
• Standardisation
• Coincidence counting

14. Coincidence counting

15. Hydrodynamic focussing

16. Correcting for coincidence

17. Factors influencing the reliability of
automated counts
• Standardisation
• Coincidence counting
• Diluents
• Discrimination thresholds
• The counting technique employed

19. The MCV and Haematocrit
• MCV – can be: derived directly
or derived from Hct and
RCC
• Haematocrit derived directly
or derived from MCV
and RCC

21. MCH and MCHC
• MCH : a derived parameter, using
Hb and RBC
• MCHC: derived from the Hb,Hct and
sometimes the MCV

22. Red cell Distribution Width
• Equivalent to the microscopic assessment
of the degree of anisocytosis
• Of some value in distinguishing
1.Fe deficiency anaemia
Thallasaemia
2.Megaloblastic anaemia
Other causes Macrocytosis

25. The WCC
• Determined by Impedance counting or
Light scattering
• Thresholds set to exclude normal platelets
• Nucleated cells usually included

26. Sources of factitiously low WCC
• Leukocyte agglutination
• Prolonged sample storage
• Abnormally fragile cells

27. Sources of factitiously high WCC
• Usually the result of failure of red cells to
lyse
• Micro clots
• Platelet clumping
• The presence of cryoglobulin

28. Automated differential counts
• Three principles used in various systems
1. Computerized pattern recognition
2. Flow cytochemistry
3. Leukocyte volume analysis

29. Computerized pattern recognition
• (computer)

30. Flow cytochemistry

31. Leukocyte volume analysis

32. Counting platelets

33. Sources of factitious platelet counts
• High counts: markedly microcytic red cells
fragmented red cells
• Low counts: Giant platelets
EDTA induced platelet
clumping
Satelitism

34. Counting reticulocytes

35. Counting Retics

37. The Hb
• Red cells lysed
• Free Hb converted to
haemoglobinsulphate
• Spectrophotometry

38. Quality control
• Accuracy
• Precision

40. The place of the automated blood
cell analyzer
• Cannot recognize all the abnormalities
that a human observer can
• Designed to produce accurate and precise
counts
• Alert the operator when a specimen has
unusual characteristics

41. Flagging
• Results should be flagged when:
1. The specimen might contain: blasts,
immature granulocytes, NRBC or
atypical Lymphocytes
2. Giant or aggregated platelets are present
or distinction between the RBC and Plt
populations cannot be made
3. Abnormalities present assoc with
factitious results

42. A result is can never be better than
the specimen