Methodologies for enumerating peripheral T lymphocytes.

Flow cytometric or manual microscopic techniques can be employed for the identification and quantitation of T lymphocytes in peripheral blood. Two flow cytometric devices (the Ortho Spectrum III and the Cytofluorograf FC200) were compared with each other and with two manual methods, each of the latter performed by two independent investigators, to evaluate the technical sensitivity and reproducibility of each method. Flow cytometry proved to be the most sensitive and consistent procedure for the enumeration of T cells. Among the manual methods examined, the enhanced immunofluorescence technique was found to be the least subjective and most reproducible.