Terminology-blood tests/MPD
Date: Fri, 24 Jan 1997 11:03:01 -0500
From: "Susan J. Leclair" <sleclair@UMASSD.EDU>
Subject: Re: to Peggy L.
MCV - mean corpuscular volume - the average size of the red cells. This is
a mathematical formula in which you divide the hematocrit by the red cell
count plus a fudge factor. Think of it as your 4th math questions "if 12
apples cost $1.20, how much does 1 apple cost?" This is an average so it
assumes a homogenous population of cells. It will be imprecise if you have
change in size.
MCH - mean corpuscular hemoglobin - similar to the MCV, it reflects that
average weight of hemoglobin in each cell. Again, it assumes a
homogeneous population of cells and is gotten by dividing the red cell
count into the hemoglobin value (plus the ubiquitous fudge factor).
MCHC - mean corpuscular hemoglobin concentration - This is just a little
bit different from the MCH in that it reflects the amount of space taken up
by the hemoglobin in the cell. It is a percentage relation between the
hematocrit and hemoglobin values. The higher it is, the "fuller" the cell
is of hemoglobin. Since hemoglobin is in a "liquid" state and since there
are enxymes and other stuff in the cell, the cell will break apart if you
try to put more than about 36% hemoglobin into it. Think putting a pint of
liquid into a cup container. More physicians rely on the MCHC than the MCH
since the hematocrit and hemoglobin are two of the more accurate and most
precise of all hematology tests. Red cell counts are not as good so this
value - since it comes from good values - is seen as a better test. Again,
this test is accurate only to the degree that the cells are homogenous.
RDW - Red cell distribution width answers the homogeneity question. It
sized every single cell and creates a type of "bell curve" (Remember from
school?). If every cell were exactly the same size, the values would be 1.
But red cells lasts for 120 days and during that time, they start out
bigger and gradually get smaller and rounded. So the best red cell
population has a little change in size (the 10 -15 value). Anything above
that suggests that there is a significant change in size and that the MCV,
MCH, and MCHC should be viewed with that in mind.
Hope that helps.
Susan J. Leclair, MS, CLS(NCA)
Professor of Medical Laboratory Science
Department of Medical Laboratory Science
University of Massachusetts Dartmouth
Dartmouth, Massachusetts 02747-2300
Date: Tue, 14 Jan 1997 11:46:24 -0500
From: "Susan J. Leclair" <sleclair@UMASSD.EDU>
Subject: Re: Education of Terms
All terms in medicine are filled with qualifications and exceptions but, as
a broad gauge, these definitions will give you an idea of what is going on.
too few platelets = thrombocytopenia - does not tell whether the low
platelets is due to
faulty production or increased useage
bruisings = purpura. Bruises can be separated intop etecchiae (very small,
freckly like small vessel bleeding), ecchymosis (flat, usually monocolored
bruises), and hematoma(large, swollen, multi-colored, may be hard).
(remember you can add a string of nouns togehter to make almost any
conbination as in
bruising due to low platelets = thrombocytopenic purpura)
too many red cells = erythrocytosis
anisocytosis = changes in the size of the red cells. Reflected in a value
of the CBC called
"MCV" (approximately 80 - 100 fL is considered average)
macrocytosis/macrocytes = red cels larger than normal. (above 100)
microcytosis/microcytes = red cells smaller than normal (below 80)
poikilocytosis = change in the shape of the red cells. Typically, red
cells are round and
biconcave. Changes such as teardrop, target (more formally known as
leptocytes and
codocytes), sickle, fragmented (schistocytes), spherocytes, etc.
desbribe the
population of abnormal cell shapes. Reflected in the CBC values "RDW"
polychromasia or polychromatophilia = staining subtility that can differentiate
younger red cells from the rest of the population. Increases in
polychromasia reflects
increased marrow production of red cells. When this increases, a
test (performed on
peripheral blood and there fore much more acceptable to patients
than a bone
marrow aspirate) variously called a reticulocyte count, absolute
reticulocyte count,
RPI will try to assess the degree of marrow involvement.
too many white cells = leukocytosis
too many granulocytes (synonyms are neutrophils, neuts, polys,
bands, segs, nonsetgs,
PMN's, grans) = neutrophilia
the presence of immature granulocytes (metamyelocytes, myelocytes,
progranulocytes) = shift to the left
too many lymphocytes = lymphocytosis
reactive lymphocytes (out moded term = atypical) = type of
lymphocyte seen during
a functional response of the immune system. These cells
are your immune response
for such diseases as measles, mumps, colds, etc. They were
unjustly believed to be
the cause of infectious mononucleosis in the 20's. Loss of
function is seen in
lymphomas and lymphocytic leukemia.
too many monocytes = monocytosis. The main phagocytic (eating)
cell in the blood
and tissue. Increases are seen as they try to clean up
dead and dying cells from
trauma (heart attacks, car accidents), fungal infections, etc.
Absolute cell counts = the percent of a cell line reported in the
differential multiplied by
the total white cell count. This clears up potential confusion
about what cells are the
problerm and how many do you have. For example: A differnetial is
done by \
classifying the first 100 cells seen. Supposed you saw 90 grans.
This may mean you
have too many neutrophils or too few lymphocytes. Using the
Absolute counts can
tell you the answer. You need a minimum of 1000 FUNCTIONAL
granulocytes to
remain uninfected. We typically do not test functionality so many
rely on the
numbers. Below this, physicians get antsy. Below 500, an
infection is assumed to be
present.
Does this help?
Susan J. Leclair, MS, CLS(NCA)
Professor of Medical Laboratory Science
Department of Medical Laboratory Science
University of Massachusetts Dartmouth
Dartmouth, Massachusetts 02747-2300
Date: Mon, 13 Jan 1997 21:35:32 -0500
From: Norm Freeburg <nfreeburg@CYBERUS.CA>
Subject: Pat, some terms
Pat,
My husband has PV, not ET - so I can't help much with symptoms and
such - pruritus (itching) IS considered a symptom of PV and it can be REALLY
BAD!!! in PV. Some Et'ers have also mentioned it.
In terminology, some of our health-care people online have given us
help with this (available in the archives, perhaps?), but I've listed some
basic terms below that I like to know when I'm reading articles/abstracts.
Please continue to keep us updated on your treatment!
Ruth
erythrocyte - red blood cell
leukocyte - white blood cell
thrombocyte - platelet
-osis (an abnormality - increase as in erythrocytosis, leukocytosis,
thrombocytosis)
-penia (a decrease as in leukopenia or blood cytopenias)
megakaryocytes - earlier forms of platelets
reticulocytes - earlier red blood cells (I think just after losing the
nucleus)
normoblast - nucleated red blood cell
-blast - premature cells ("nucleated precursers")
hemopoiesis - blood cell production (also erythropoiesis,
thrombopoiesis
etc.)
extramedullary - outside of the bone marrow as when blood production
occurs outside of the marrow in myeloid metaplasia
splenomegaly - enlarged spleen (as when it is producing blood or
full of
cells)
hepatomegaly - enlarged liver (ditto)
hyperplasia - an abnormal increase in cells - as in the marrow in
myeloproliferative disease
dysplasia - an abnormal decrease in cells - as in the marrow in myeloid
dysplasia
myeloid - pertaining to the marrow (bone) as in myelofibrosis or
myeloproliferative
myeloblast - an early form of the granular white blood cells
(leukocytes which are neutrophils, basophils, or
eosinophils)