Cytofluorometric methods for assessing absolute numbers of cell subsets inblood

The enumeration of absolute levels of cells and their subsets in clinical s amples is of primary importance in human immunodeficiency virus (HIV)+ indi viduals (CD4+ T- lymphocyte enumeration), in patients who are candidates fo r autotransplantation (CD34+ hematopoietic progenitor cells), and in evalua ting leukoreduced blood products (residual white blood cells). These measur ements share a number of technical options, namely, single- or multiple-col or cell staining and logical gating strategies. These can be accomplished u sing single- or dual-platform counting technologies employing cytometric me thods, Dual-platform counting technologies couple the percentage of positiv e cell subsets obtained by cytometry and the absolute cell count obtained b y automated hematology analyzers to derive the absolute value of such subse ts. Despite having many conceptual and technical limitations, this approach is traditionally considered as the reference method for absolute cell coun t enumeration. As a result, the development of single-platform technologies has recently attracted attention with several different technical approach es now being readily available. These single-platform approaches have less sources of variability. A number of reports clearly demonstrate that they p rovide better coefficients of variation (CVs) in multicenter studies and a lower chance to generate aberrant results. These methods are therefore cand idates for the new gold standard for absolute cell assessments. The current ly available technical options are discussed in this review together with t he results of some cross-comparative studies, Each analytical system has it s own specific requirements as far as the dispensing precision steps are co ncerned. The importance of precision reverse pipetting is emphasized, Issue s still under development include the establishment of the critical error r anges, which are different in each test setting, and the applicability of s implified low-cost techniques to be used in countries with limited resource s. Cytometry (Comm. Clin. Cytometry) 42:327-346, 2000. (C) 2000 Wiley-Liss, Inc.