New and improved: hematology analyzers
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
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.