I am having trouble accurately counting the number of lymphocytes, monocytes, and neutrophils in human blood samples isolated through density gradient using dextran.

We usually count PBMCs isolated with Ficoll in the cytometer, and it is accurate enough. When done with dextran samples, cells are overstated and we cannot properly perform functional analysis.

Is there any optimal way to count leucocytes isolated with dextran by flow cytometry or any other technique?