Hemacytometer Cell Count Distributions: Implications of Non‐Poisson Behavior

The variance of observed cell counts using a hemacytometer was analyzed. The variance was found to be greater than expected under the normally assumed Poisson distribution because of variations in the volume of the counting area. Furthermore, counts from the two sides of the hemacytometer were found to be correlated. Total cell count on a hemacytometer was better described using a normal distribution with quadratic variance, N(λ,λ + σλ2), with σ=0.012. Because hemacytometer cell counts are not Poisson distributed, modified counting protocols are recommended.