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)