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*** LAB NEWS ***
CBC VS. CBC DIFFERENTIAL
The Hematology Laboratory continues to receive questions about which
specific tests are performed when either a CBC or a CBC DIFFERENTIAL
is ordered. Please note the following:
1.
A CBC is comprised of the following, as performed by an automated
analyzer:
* WBC count
* RBC count
* Hemoglobin
* Hematocrit
* MCV |
* MCHC
* RDW
* Platelet count
* MPV
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2.
A CBC DIFFERENTIAL (CBCD) is comprised of all the tests performed
in the CBC as above PLUS the following:
* Lymphocyte %
* Monocyte %
* Neutrophil %
* Eosinophil %
* Basophil %
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* Lymphocyte #
* Monocyte #
* Neutrophil #
* Eosinophil #
* Basophil #
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3. Automated differentials, manual differentials, and blood
films scans are NEVER performed when a CBC is ordered. If, for example,
the results of the CBC are abnormal, and a differential is warranted,
the laboratory cannot add it without an order from the healthcare
provider.
4. If a CBC DIFFERENTIAL is ordered, the automated 5-part
differential will be reported unless one or more of the following
is true, in which case a manual differential will be performed:
* WBC < 4000/ul or > 15,000/ul
* Basophil > 3.0%
* Lymphocytes >60.0% on patients >6 years old
* Variant lymph flag
* Suspect blast flag
5. In some cases, a blood film scan will be performed when
a CBC DIFFERENTIAL is ordered. Blood film scans are performed in
order to verify aberrant WBC or platelet flags reported by the automated
cell counter. If WBC abnormalities are seen on a blood film scan,
a full 100 cell manual differential is performed. Blood film scans
are performed when:
* Neutrophil > 80% accompanied by a suspect band flag
* Neutrophil # > 8500/ul
* Monocyte % > 15.0
* Eosinophil % > 15.0
* All R (Region) flags
* Hemoglobin < 8.0 g/dL or > 18.0 g/dL: For morphology
* MCV < 70.0fl or > 110fl: For morphology
* RDW > 20.0 or R (Region) flag: For morphology
* Platelet (PLT) < 70,000 on new patients or < 50,000 on all
other patients
* All PLT and/or mean platelet volume (MPV) R (Region) flags
6. Other notes:
a. Only one manual differential will be performed on a patient per
24-hour period.
b. Manual differentials are now done during the midnight shift as
staffing permits.
c. Specimens are stored in the laboratory for only 24 hours, after
which they are discarded.
d. Physicians still have the option to order only a WBC count, hemoglobin/hematocrit,
or platelet count if these are the only tests indicated.
7. If you have any questions about these tests ordering please
contact the Hematology Laboratory at 4-2375, or myself (4-2601,
pperrotta@notes.cc.sunysb.edu).
- Peter L. Perrotta, M.D.
Chief, Hematology Laboratory
Ph 631-444-2601 Fax 631-444-2653
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