Particle classification from light scattering with the scanning flow cytometer

Background: The differential light-scattering pattern, an indicatrix, provi des the most complete characterization of the optical properties of a parti cle. Particle classification can be performed on the basis of particle para meters retrieved from the indicatrices. This classification extends the abi lity of flow cytometry in particle recognition. Methods: The scanning flow cytometer (SFC) permits an acquisition of traces of light scattering signals, i.e., native SFC traces, from single particle s. The acquired native SFC traces are transformed into indicatrices. The pe rformance of the SFC in measurements of indicatrices has been demonstrated for the following particles: lymphocytes, erythrocytes, polystyrene particl es, and milk-fat particles. Results: The structure and profile of the indicatrix for each particle type have been found to be unique. Classification of polystyrene particles has been performed on the basis of the map formed by particle refractive index and size. The polystyrene particles were classified using this map into dif ferent size categories ranging from 1.4-7 mu m, with a size deviation of 0. 07 mu m. Conclusions: The method based on analysis of native SFC traces shows better performance in particle classification than the method based on the partic le refractive index and size map. The classification performance of the SFC will be useful, for example, for particle sorting and particle identificat ion, and with additional fluorescent measurements may have applications in multiparameter particle-based immunoassay. Cytometry 37:215-220, 1999. (C) 1993 Wiley-Liss, Inc.