Feature Story

New and improved: hematology analyzers

December 2002
Raymond D. Aller, MD
William G. Finn, MD

The December, 2002, Survey may be located here.

Hematology cell counters continue to provide an ever-broader scope of capabilities. Technologies that were leading edge a few years ago, such as reticulocyte enumeration, are now routine. Methods that heretofore required much manual manipulation—such as CD4 counts—can now be incorporated as part of the random-access CBC specimen stream on instruments such as the Abbott Cell-Dyn 4000. Food and Drug Administration approval of quantitative nucleated red blood counts on several instruments now permits automated handling of patients with a variety of pathologic states.

For 25 years, the holy grail in the automated counting of the WBC differential has been the enumeration/quantification of immature granulocytes. We continue to debate with clinical colleagues who insist they must have a manual differential because they want to know if "bands" are numerous. It doesn’t faze them that study after study demonstrates that the "band count" is terribly imprecise and nonreproducible. At least one manufacturer has submitted applications to the FDA for clinical use of the "immature granulocyte" channel. This advance has great potential for the precise and accurate quantitation of immature granulocyte forms (the collective total of promyelocytes, myelocytes, and metamyelocytes). Ironically, the clinical significance of automated immature granulocyte counts is difficult to measure at present, since the existing literature is heavily weighted toward only band counts and not extended immature granulocyte counts. We do hope to see these immature granulocyte counts take hold and, finally, eliminate the use of the manual band count.

Bayer’s reticulocyte hemoglobin measurement is useful in the early diagnosis of iron deficiency and in monitoring response to treatment.

Another interesting new channel is hematopoietic progenitor cells, or HPCs, available on the Sysmex XE-2100. In some settings, this will permit stem cells to be quantitated (for example, in an apheresis product) without requiring a direct CD34 study on a flow cytometer. This study is based on differential membrane lipid content. HPCs have lower membrane lipid content than mature leukocytes and are preserved after treatment with a lysing agent.

With increasing routine automation of assays that previously required the use of flow cytometers, we may see flow cytometers redirected to more in-depth analyses of cell structure and function—the emerging field of cytomics.

The rate-limiting step on the introduction of new diagnostic modalities is no longer a matter of how quickly the technology can be developed, licensed, and deployed. Far more important is how quickly medical practitioners embrace the new technologies and incorporate them into their routines.

On pages 37–46, we profile 18 instruments from five manufacturers. As always, we urge you to talk to those who are using these instruments (or their predecessors) to find out what you can expect from the manufacturer in terms of service, support, and reliability.

Those selecting hematology instruments can no longer base their decisions solely on the lowest-price instrument. Medical considerations may dominate. Perhaps the patient mix requires a parameter that is available only on certain instruments, for example. Operational considerations may be paramount—reliable, high-throughput, easy-to-use instrumentation may be more crucial than having all the newest parameters on a more difficult-to-use instrument. The fiscal effect of eliminating flow cytometry for high-volume studies, such as CD4 or CD34, may outweigh a higher cost-per-test on CBCs. Do not let your purchasing agent make the decision without your involvement.

Dr. Aller is based in Vista, Calif., and can be reached at raller@ earthlink.net. Dr. Finn is a member of the CAPHematology/Clinical Microscopy Resource Committee. He is clinical associate professor of pathology, director of hematopathology, and associate director of clinical pathology at the University of Michigan, Ann Arbor.