Automated differential leucocyte counters: an evaluation of the Hemalog D and A comparison with the Hematrak. I. Principles of operation; reproducibility and accuracy on normal blood samples

Basophil counting in hematology analyzers: time to discontinue?

Basophils (basophilic granulocytes) are the least abundant cells in blood. Nowadays, basophils are included in the complete blood count performed by hematology analyzers and therefore reported in practically all patients in whom hematologic investigations are requested. However, hematology analyzers are not reliable enough to report clinically useful results. This is due to a combination of very high analytical imprecision and poor specificity, because the chemical and physical methods used for basophil counting in hematology analyzers are ill-defined and thus basophils are not well recognized by the analyzers. As a result, false basophil counts are quite common. In view of increasing analytical performance demands, hematology laboratories should stop reporting basophil counts produced by hematology analyzers. Suggestions for alternative pathways are presented for those situations where basophils are of clinical relevance.

A comparison of the screening ability of two automated leukocyte differential counters

The ability to screen out abnormal leukocyte differential counts by the H 6000TM and the Hematrak 590TM has been evaluated, using the visual 100 cell differential as a reference. Optimization of the discrimination levels for both instruments by the use of linear regression procedures and "Receiver Operating Characteristics (ROC) curves" and its impact on their performance characteristics is discussed. The overall sensitivity for 314 outpatient/188 inpatient samples was 0.84/0.94 for the H 6000 and 0.84/0.88 for the Hematrak, respectively. The overall specificities for out-/inpatient samples were found to be 0.61/0.44 and 0.47/0.30 for the H 6000 and the Hematrak, respectively. Both instruments had very similar screening abilities for the detection of abnormal leukocyte differential counts. However, the H 6000 flags correlated better with the visual findings than the Hematrak flags as demonstrated by the parameter-sensitivity and predictive value calculations and by the ROC curves.

Adaptation of the May-Grünwald-Giemsa staining method for automated differential counting of blood leukocytes by a Hematrak analyzer

The selection of exact pH (6.85/6.90) concentrations of the stains and staining times made it possible to use the May-Grünwald-Giemsa (MGG) staining method for smears studied with a Hematrak model 240 automated differential leucocyte counter. The differences between the smears stained by the method of Wright according to the recommendations of the manufacturer and the present MGG-modification resulted in non-significant differences in the recognition of various types of leucocytes. The differences between the manual method and those obtained by Hematrak for the MGG-stained samples with normal total leucocyte counts were nonsignificant with all types of leucocytes except basophils, which were underestimated by the instrument. The present staining procedure was adequate in studying of neutrophilias. When samples with lymphocytosis or with immature cells were examined, too few lymphocytes and immature cells and too many monocytes were obtained by the instrument, as compared to the manual method.