This lecture introduces you to some of the major applications of flow cytometry in the clinical laboratory. I have also included a section on DNA analysis. Although , at present, it has limited clinical application, it is important research tool and may find clinical application in the future. This lecture is fairly long. You do not need to learn all its content, just to be aware of the different applications.
The largest number of flow cytometers, particularly bench-top instruments, is to be found in routine clinical laboratories. The most common application is still the classification of leukaemias. The range of other applications, and the laboratories using them, is growing rapidly.
Immunophenotypic analysis of leukaemias and lymphomas
Immunophenotyping by flow cytometry is an important tool in the diagnosis and staging of patients with a haematological disorder. The immunophenotype is used to
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provide prognostic information
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select markers for detecting minimal residual disease during treatment.
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Normal blood cells develop from stem cells in the bone marrow in a progressive series of differentiations, branching off to give different lineages of cells (for example, myeloid or lymphoid, T cell or B cell), each of which has a distinct maturation pathway.
At each stage, the cells carry a distinctive set of markers. Malignancies can arise at different stages in the development of a cell. A leukaemia or lymphoma will express a specific set of markers depending on the stage and pathway of differentiation and they are classified accordingly. Tumours may, however, lack certain markers or express aberrant proteins; there are even biphenotypic leukaemias.
The initial evaluation is normally made with a limited panel of antibodies using them in three or four colour combinations. The panel selected will depend on the initial clinical diagnosis. An example of a screening panel for acute leukaemias is given in Table 5.1.
The results from the initial screen may indicate the need for further testing with an extended panel that is more specific for a particular disease.