This study evaluated reticulocyte counting and measurement of reticulocyte cellular indices with the Miles H*3 blood analyzer, a new instrument that combines the Technicon/Miles technology for blood cells counting with a staining technique allowing counting of reticulocytes, quantification of staining intensity and measurement of reticulocyte cellular indices. Reticulocyte counts obtained with the Miles H*3 analyzer were compared with those obtained by manual counting, flow cytometry (thiazole orange method) and by the Sysmex R-3000 (Baxter Diagnostics) reticulocyte analyzer. Reticulocyte counting with the Miles H*3 showed excellent precision, and linearity in the range tested (1.1-49% and 1-72% reticulocytes, respectively, with two different protocols) with no significant carryover. Reticulocyte counts were stable after storing blood samples for 72 hours at 4 degrees C. Comparison of the four different methods, showed an acceptable intraclass correlation between Miles H*3 and Sysmex R-3000 (intraclass correlation coefficient, [r(i)] = .952), Miles H*3 and flow cytometry (r(i) = .922), and Sysmex R-3000 and flow cytometry (r(i) = .938). There was no satisfactory correlation between any of the three automated methods and the values obtained with manual counting of reticulocytes (r(i) = .538-.755), consistent with the well known imprecision of the manual technique. For a group of normal pediatric subjects, age 1-10, we obtained the following values (+/-SD) of reticulocyte indices: mean corpuscular volume 97.6 +/- 4.7 fL; cell hemoglobin concentration mean 28.2 +/- 1.4 g/dL; cell hemoglobin content 26.7 +/- 1.6 pg. We determined the direct cost, including depreciation, of the manual and instrumental methods. Cost/test varied from $1.61 for manual method to $6.03 for the Sysmex R-3000. Cost/test for flow cytometry and Miles H*3 were $3.34 and $3.49, respectively.
