Expression strength key
From haematologyetc.co.uk
The term "expression strength" effectively reflects how strongly a molecule is expressed by neoplastic cells. This is based on the intensity of the observed fluorescence. The term can be helpful in flow cytometric diagnosis: For example identifying the characteristically weak expression of CD79b by CLL cells, or the characteristically strong expression of CD25 by the cells of HCL.
The term is however associated with some difficulties since antibodies and fluorochromes can differ between laboratories, and the judgment of strong (bright) or weak (dim) exprssion is partly subjective based as there is no gold standard to define expression level. A widely used definition uses the term "dim" when a population of cells are positive for a given antigen, but have a mean fluorescence intensity that is lower than that of a positive normal cell population, or "bright" if fluorescence is higher intensity than the control. The control cell is taken as the most closely related normal population.
Given the fairly subjective nature of the term "expression strength", the table only records fluorescent intensity if it has diagnostic importance, using the terms strg (strong/bright fluorescence) or wk for (weak/dim fluorescence). We use the term var when the expression can differ markedly within a single case