A Body fluids contain a
number of cell types — nucleated and non-nucleated cells (red blood cells).
The nucleated cells include hematopoietic and non-hematopoietic cells. The
hematopoietic cells are comprised of nucleated red blood cells, lymphocytes,
monocytes, and neutrophils. The non-hematopoietic cells include mesothelial
cells and histiocytes/macrophages. A third group of nucleated cells are the
malignant cells, which originate from hematopoietic cells (lymphoma cells or
leukemia blasts) or non-hematopoietic metastatic tumor cells (carcinoma,
melanoma, sarcoma, et al).
Body-fluid cell counts are usually performed manually
in a hemocytometer when the cell numbers and/or sample volume are deemed to
be too small for automated analysis. These non-stained counts yield an
absolute cell count and the ratio of nucleated to non-nucleated cells.
Afterwards, a cytospin slide is stained and reviewed to obtain a
differential count of 100 cells. We include hematopoietic (e.g.,
lymphocytes, monocytes, neutrophils) and non-hematopoietic nucleated cells (mesothelial
cells, macrophages, et al) in the differential. Another category that is
included in the differential count is called “atypical cells.” The atypical
cells could be blasts, lymphoma cells, and other metastatic tumor cells. The
atypical cells are counted only when they are discernible as single cells
and they can be described morphologically in a concise way. Large groups or
clusters of atypical cells are not included in the differential and are
reported separately. All cases with atypical cells should be sent for
pathologist review if there is no previous diagnosis pertaining to the
findings. Methods and principal cell types can be found in the Clinical and
Laboratory Standards Institute Guideline: Body Fluid Analysis for Cellular
Composition.1
—Winfried Reichelt, MD, PhD
—Eric Nutt, MT(ASCP)
—Guang Fan, MD, PhD
Oregon Health and Science University
Portland, OR
Reference
- Clinical and Laboratory Standards Institute. Body
Fluid Analysis for Cellular Composition. Proposed Guideline. Wayne, PA:
Clinical and Laboratory Standards Institute; 2005. CLSI document H56-P.
Thawing frozen specimens
Q I find lots of info
on freezing specimens but not any on how to thaw them. Do you have any
advice?
A You are right that there is
no shortage in the literature on how and when to freeze a specimen, but
thawing instructions are a little harder to find. In part, I suspect that is
due to the relative simplicity of the process. For most analytes, thaw
specimens at room temperature and mix by inversion before testing. Thawing
in a 37^0C water bath or heat block may be acceptable unless the specimens
are thermolabile. When such specimens are neglected and allowed to stay at
warm temperatures, heat sensitive analytes may deteriorate and render
inaccurate results.
—Dennis Ernst, MT(ASCP)
Director
Center for Phlebotomy Education
Ramsey, IN
Further reading
Clinical and Laboratory
Standards Institute. Collection, Transport, and Processing of Blood
Specimens for Testing Plasma-Based Coagulation Assays and Molecular
Hemostasis Assays; Approved Guideline—Fourth Edition. Wayne, PA: Clinical
and Laboratory Standards Institute; 2008.CLSI Document H21-A5.
Dark field microscopy for syphilis
Q I have a new
STD-clinic physician who wants to perform dark field microscopy for
syphilis. How would you suggest I make sure this physician is competent? We
do not perform this test in our own laboratory.
A Let us start by asking
whose responsibility it is to ensure the physician's competency. This
depends on the licensing and accreditation of your lab and your
organization's structure. If your lab's license covers microscopy
performed in clinics and you take responsibility for the quality of
point-of-care testing throughout the organization, it is your
responsibility to determine the competency of individuals performing
those tests. If, however, each testing site is responsible for its own
license, it can be politically difficult for the lab to look at the
competency of individuals performing tests outside of it jurisdiction.
It then becomes the STD physician's department's responsibility to
attest to his competency.
Dark field microscopy requires proper equipment,
knowledge, and experience. Many STD physicians have acquired this in
their training and prior practice. It would not be appropriate to have
the laboratory test the physician's competency if there is no one in the
lab with similar knowledge and experience.
There are some alternative ways you can determine
the physician's competency in this skill:
- Ask for documentation from his previous practice or training
program, if the physician has
recently completed training. - Ask for a determination and documentation of competency from an
expert in an STD clinic in
your area. - If the physician has the knowledge and experience with dark
field microscopy for spirochetes,
you could ask a peer of
his practicing in a different STD clinic to certify his competency.
—Daniel M. Baer, MD
Professor Emeritus
Department of Pathology
Oregon Health and Science University
Portland, OR
Daniel M. Baer, MD, is
professor emeritus of laboratory medicine at Oregon Health and Science
University in Portland, OR, and a member of MLO's editorial advisory
board.
