Estimation of Erythrocytes from a Blood Smear by a “Dry Chamber” Method

Summary

A method is described that permits estimation of erythrocytes from a blood smear. A specific optical setting is used yielding a ratio of the “Dry Chamber Unit” to the hemacytometer unit of 1: 0.72. On the blood smear a usable urea is determined. Its boundaries are described. The midpoint fixes the position of the Optimal Micrometer Square. Within this area the erythrocytes are counted in the same manner as done for the hemacytometer method. The average number of erythrocytes of 5 ocular micrometer squares is used for the estimation of the equivalent RBC number found with the hemacytometer method. A total of 2,000 comparative counts have been made on bloods ranging from 720,000 to 8,750,000 cells per mm³. The Dry Chamber Method yields totals that are comparable with that of the hemacytometer. The quantitative error of the Dry Chamber count is within ±200,000, the standard error allowed for the counting chamber.