Estimation of lymphocyte percentage and number on the Coulter Counter, Model S Plus Phase II.

The Coulter Counter Model S Plus Phase II provided precise measurements of lymphocyte percentage and count and carry-over was negligible. Lymphocyte percentage values agreed well with those from the stained blood film except when the percentage was high and in these circumstances the instrument gave underestimates. When making artificial mixtures with increasing lymphocyte count a progressive underestimation of the lymphocyte percentage was also noted. The display of leucocyte volume distribution was found to be a useful attribute particularly when the instrument alerted the operator to "rejected" profiles. Rejection by the instrument proved to be a helpful function occurring in the myeloid leukaemias, erythroblastosis, and in some cases when the lymphocytes differed from normal--for example, glandular fever and chronic lymphocytic leukaemia.