CORRECTION OF BONE-MARROW NUCLEATED CELL COUNTS FOR THE PRESENCE OF FAT PARTICLES

Although the use of bone marrow transplantation has increased greatly in recent years, the quality control procedures used in bone marrow pr ocessing laboratories remain less than ideal. Accurate marrow total nu cleated cell (TNC) counts are essential for effective monitoring of bo ne marrow collection and processing. Aspirated marrow is variably cont aminated by fat particles, resulting in overestimation of marrow TNC b y automated analyzers. A recently-marketed hematological analyzer (Cob as-Helios; Roche Diagnostic Systems, Branchburg, NJ) offers the potent ial to correct marrow TNC counts for fat particles using available sof tware. The authors investigated the accuracy of corrected TNC counts o n 21 marrow samples, using a visual chamber count as the reference met hod. The correction methods studied were software correction, using th e Cobas-Helios differential system, and replacement of the sample plas ma with saline, Uncorrected automated marrow TNC counts (mean, 28.4 X 10(9)/L) were significantly higher than the visual reference counts (m ean, 23.1 X 10(9)/L). Neither the mean corrected automated count (24.3 X 10(9)/L) nor tile mean saline replaced count (24.6 X 10(9)/L) diffe red significantly from the mean visual reference count. For both the c orrected automated and saline replaced counts, 20 of the 21 data point s (95%) fell within a 95% confidence interval computed for the referen ce method. The authors conclude that both the corrected automated meth od, using the Cobas-Helios, and the saline replacement method are acce ptable alternatives to the visual chamber count.