Use of the new Coulter MAXM for leucocyte differentials.

The Coulter MAXM is an automated instrument designed to give a complete haematological profile including cell counts and WBC differential (DIFF). The WBC DIFF is determined by tridimensional flow cytometry on the basis of cell volume, light scattering and conductivity (VCS technology). Evaluation of the MAXM DIFF was performed by comparison with microscopic examination of blood smear. A total of 467 samples were studied by the MAXM and reference techniques, according to a standard protocol employed in our laboratory to define the criteria for smear examination. Good correlation was obtained between the two methods in non-flagged samples and those flagged only with an isolated "Imm Gran" message. In a group of 407 non-haematological and 60 haematological patients, there were 12 (2.6%) false positive and 5 (1.1%) false negative reports, all in non-haematological cases and the five false negative results corresponding to no more than minor abnormalities. The Coulter MAXM was thus shown to be an excellent haematology analyser. This instrument was capable of detecting significant abnormalities of blood smears with a sensitivity of 97.9%, a specificity of 94.7% and a global efficiency of 96.3% in the samples examined in the present study.