Abstract: This disclosure describes the development of a sample preparation, measurement, and analysis method that permits accurate characterization of red blood cells, platelets, and white blood cells, including a 3-part differential of the white blood cells count, to be performed on small volumes of a biological sample. This method is compatible with compact and portable instrumentation that permits the sample collection to be performed in a subject's home and analysis to be performed elsewhere by transmission of the data to a laboratory or doctor's office.