In February 1971, Mayo Clinic's Routine Hematology Laboratory put into service a new instrument—the Coulter Model S—which automatically determines red and white cell counts, hemoglobin, hematocrit, mean cell volume, mean cell hemoglobin and mean cell hemoglobin concentration.
The instrument incorporates the measuring devices of six Coulter Counters. The instrument aspirates 1.3 ml. of blood from the sample tube. Most of this blood is used to flush out the previous sample from the system and only a small portion of it is used for the determinations. The blood is diluted and mixed within the diluter module and is propelled through the system by a pneumatic power supply. Measuring devices respond with signals which are translated electronically into numbers which appear on the imprinted form.
The Model S was thoroughly evaluated in the laboratory over a six-month period and was proved to be dependable, fast and, precise. Reproducibility of determinations of hemoglobin concentration, hematocrit and red and white cell counts was excellent.
Coulter Model B instruments are still used in the laboratory for platelet determinations, and sedimentation rates are determined by manual methods. Differential counts and reticulocyte counts are still made by microscope visualization.