FLOW-CYTOCHEMICAL DIFFERENTIAL LEUKOCYTE ANALYSIS WITH QUANTITATION OF NEUTROPHIL LEFT SHIFT - AN EVALUATION OF THE COBAS-HELIOS ANALYZER

The Cobas-Helios (Roche Diagnostic Systems, Inc., Branchburg, NJ) is a new, fully automated hematology analyzer that performs a complete blo od count and differential leukocyte count (DLC), classifying leukocyte s by flow-cytochemical technology. The DLC component of the Cobas-Heli os was evaluated according to the National Committee for Clinical Labo ratory Standards H20-A protocol. Instrument performance was acceptable with respect to all parameters investigated, including imprecision, i naccuracy and clinical sensitivity for the identification of quantitat ive and qualitative leukocyte abnormalities. In a minority of samples with neutrophil left shift, neutrophils tended to overlap the monocyte domain, resulting in overestimation of monocytes and underestimation of neutrophils. This problem did not affect clinical sensitivity and w as generally associated with a positive instrumental left-shift flag. Flags for the identification of specific qualitative abnormalities of the leukocyte population (atypical lymphoid cells, nucleated red cells , blast cells, immature granulocytes and neutrophil left shift) perfor med well. In addition to a conventional five-part DLC, the Cobas-Helio s also identifies and quantitates atypical lymphoid cells and ''large immature cells,'' the latter corresponding to bands and immature granu locytes. Counts of atypical lymphoid cells and large immature cells co rrelated well with the equivalent cell classes as enumerated by the re ference method of the National Committee for Clinical Laboratory Stand ards. The Cobas-Helios offers the most reliable quantitative index of neutrophil left shift currently available in a commercial automated DL C analyzer.