A new type of hemocytometer and its application to measurement of mean corpuscular diameter of red blood cells

Abstract

A new type of hemocytometer was divised for simultaneous measurement of the mean corpuscular diameter (MCD) and red cell count (RCC). The counting chamber of the new hemocytometer has entirely the same size and section as the Thoma's, but has silver plated stripes. The edgelines of the stripes run regular intervals of 12.5μ, as shown in Fig. 1. This silver plating does not interfere counting, as cells and lines are perceptible through the plating film. The principle to measure MCD depends upon the fact that the number of red cells crossing the edgelines are proportional to the ratio of the diameter of red cells to the distance between edgelines. As shown in Fig. 2,the probability, Px, of red cells crossing the lines against all the red cells in the chamber is equal to the ratio of the diameter of red cells, x, to the distance between the lines, l.Px=x/l E(Rx)/(Nx)=Px E(Rx)=N/lx・f(x)・dx Rx : the number of the red cells, of which diameter is x, crossing the lines. Nx : the number of the red cells, of which diameter is x, exist in the chamber. E(Rx) : the expectation of Rx f(x) : the probability density function of Nx N : the total number of the red cells in the chamber Hence, E(R)=N/l∫^∞_0x・f(x)・dx=N/lx^^- E(R) : the expectation of R R : the number of the red cells, crossing the lines x^^- : mean diameter of the red cells : MCD x^^-=l・E(R)/N=l・P P : the probability of the red cells crossing lines rgainst all the red cells in the chamber Let p be the relative frequency of R against N, p=R/N … 1) p=p+Δp From the property of binominal distribution, Δp=1/2sin(2sin^^-1√ <p>)sin(4・1/√<4N>・180/π)… 2)Δx^^-/x^^-=Δp/p … 3) From these equations 1), 2), and 3), MCD is calculated simultaneously with the error of measurement, Δx^^-, which means ahalf of confidence interval. Table 1 shows the error of the measurement of MCD, calculated with equation 2), under 95 % of confidence coefficience against several RCC vs MCD. If Thoma's hemocytometer is used to measure MCD, the error of the measurement Δx is ± 0.85μ, while the new type of hemocytometer gives ± 0.24μ against RCC 500 × 10^4/mm^3,MCD 8.0μ of the red cells. This new type of hemocytometer is expected to have a practical value.