Evaluation of monocyte counting with two automated instruments by the use of CD 14-specific immunomagnetic Dynabeads

Accurate determination of monocytes can be a problem with automated haematological analysers as well as with visual microscopy. We have compared monocyte counts from our two routine automated instruments, Technicon H*1 and Sysmex NE-1500. In the NE-1500 the monocyte counts appear to increase with increasing concentrations of neutrophils, compared with the H*1 results. The accuracy of the monocyte counts was assessed using Dynabeads M-450 CD14. These uniform magnetizable polystyrene beads coated with monoclonal antibody specific for CD14 membrane antigen isolated monocytes from the blood samples. The influence of this depletion on the monocyte counts and histograms from the two instruments and by visual microscopy were compared. On average 90% of the monocytes counted by visual microscopy were removed from six blood samples. In the same samples the beads removed an average of 75% of cells identified as monocytes by the H*1 but only 49% of those identified as monocytes by the NE-1500. These Dynabeads can be a useful tool in evaluating monocyte identification in different haematological situations and for manufacturers developing technology for automated leucocyte differential counting.