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A blood specimen containing cold agglutinins of high titer gave obviously erroneous values when counted on Coulter equipment in a laboratory with a low ambient temperature. Owing to microagglutinates, the Model A and Model F counters gave erroneously low erythrocyte counts, and therefore high calculated values for mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH). Three Model S counters gave low erythrocyte (RBC) counts, high observed MCV values, and low calculated hematocrits (hematocrit = MCV X RBC). The resulting values for MCH and mean corpuscular hemoglobin concentration (MCHC) were impossibly high. Warming the diluent entering the counter not only eliminated these spurious values but resulted in more precise readings in general. The authors recommend that temperature control be added to the Coulter Model S equipment.
Hattersley et al. (Thu,) studied this question.