AUTOMATED RETICULOCYTE COUNTING AND MEASUREMENT OF RETICULOCYTE CELLULAR INDEXES - EVALUATION OF THE MILES-H-ASTERISK-3-BLOOD-ANALYZER

This study evaluated reticulocyte counting and measurement of reticulo cyte cellular indices with the Miles H3 blood analyzer, a new instrum ent that combines the Technicon/Miles technology for blood cells count ing with a staining technique allowing counting of reticulocytes, quan tification of staining intensity and measurement of reticulocyte cellu lar indices. Reticulocyte counts obtained with the Miles H3 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 H3 showed excellent precision, and linearity in the range tested (1.1-49% and 1 -72% reticulocytes, respectively, with two different protocols) with n o significant carryover. Reticulocyte counts were stable after storing blood samples for 72 hours at 4 degrees C. Comparison of the four dif ferent methods, showed an acceptable intraclass correlation between Mi les H3 and Sysmex R-3000 (intraclass correlation coefficient, [r(i)] = .952), Miles H3 and flow cytometry (r(i) = .922), and Sysmex R-3000 and flow cytometry (r(i) = .938). There was no satisfactory correlati on between any of the three automated methods and the values obtained with manual counting of reticulocytes (r(i) = .538-.755), consistent w ith 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 hemogl obin content 26.7 +/- 1.6 pg. We determined the direct cost, including depreciation, of the manual and instrumental methods. Cost/test varie d from $1.61 for manual method to $6.03 for the Sysmex R-3000. Cost/te st for flow cytometry and Miles H3 were $3.34 and $3.49, respectively .