What laboratory analysis is most helpful for determining the number of mature T cells in suspected DiGeorge's syndrome?

Flow cytometry is the most helpful laboratory analysis for determining the number of mature T cells in suspected DiGeorge's syndrome. This technique allows for the detailed characterization of T cell populations by using fluorescently labeled antibodies that recognize specific surface markers associated with T cells.

In DiGeorge's syndrome, there is a congenital deficiency of T cells due to thymic hypoplasia. Flow cytometry can quickly quantify the absolute numbers of CD3-positive T cells, which are a key marker for mature T lymphocytes. Additionally, flow cytometry can differentiate between subsets of T cells (such as CD4+ and CD8+ cells), providing valuable information about the immune status of the individual.

Other options, while useful in various contexts, do not provide the specific information needed for assessing T cell maturation in DiGeorge's syndrome. A complete blood count offers limited insight into immunological status, the nitroblue tetrazolium test assesses neutrophil function rather than T cell quantity, and T-cell enzyme assays focus more on functional aspects rather than providing a direct count of mature T cells.