Fluorescence intensity as a quality control parameter in clinical flow cytometry.

The fluorescence intensity (FI) and percentage of immunostained peripheral blood lymphocytes (PBLs) were tested as parameters for monitoring quality control of monoclonal antibodies (MoAbs) and the staining procedure. Several potential variables were addressed, including optimal dilutions of MoAbs, standardization of instrument functions with fluorescent microspheres, stability of day-to-day fluorescence detection with fluorescent fixed cells, and effects of separation method and storage conditions on FI and PBL antigens. Although some small (but statistically significant) changes were found in certain tests, in general the FI and percentages of MoAB-positive human PBLs provided information useful in a standardized flow cytometry quality control program. This type of standardization and quality control facilities early discovery of methodologic and reagent problems in the clinical laboratory, as well as the ability to routinely evaluate disease states associated with abnormal antigen density.