Re: serum & plasma

[Guest guest]

Hi, Sue B.

>Thanks for the great explanation of the difference between serum and

>plasma.

>

>Can you give us some examples of why one or the other would be necessary

>for a particular test?

>

And can you suggest any tricks that would help me REMEMBER which is which?

>(e.g., supine--on your spine)

For a memonic, I don't know of anything really easy. The only one I can

think of works if you are familiar with rugby - serum sounds like (rugby)

scrum, all clotted together.

For tests, on looking through my chart of standard lab values (back of the

medical dictionary - very handy!) I saw that most used serum. (This includes

calcium.) Many tests can be done with either serum or plasma.

Many of the enzyme tests are functional tests of enzymes that require

calcium and/or magnesium to operate. All of the common anticoagulants except

heparin work by binding calcium (needed for clotting). They also bind Mg

strongly. So using any of these anticoagulants means that the enzymes can no

longer work; the functional test then comes up 0 even if there is enzyme

present, just because it can't work.

Complement tests use plasma (EDTA as anticoagulant), probably because clots

would bind complement components. Fibrinogen testing is done on plasma.

Cortisol uses plasma; so do fluoride, potassium, insulin, and testosterone.

OTOH, sodium can be done on either; zinc requires serum. So I can't see any

simple general pattern other than that serum is most common.

Jerry

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[Guest guest]

Hi, ,

>You sound very knowledgeable. How did you learn all of these things?

Thanks - got a graduate degree in biochem and did a spell as a QC lab

manager for a biopharmaceutics company. Also have an ex-med tech as a wife

and having roomed with a pharmacy student in college helped.

>I'm going to try and take advantage of your knowledge if that is ok? : )

What we're here for, right?

>I have very high plasma volume. Is there a way to test what is in that

>plasma?

That is what most blood tests do -- tests on serum will still reflect what

is in the plasma to start with in the majority of cases.

>I have a chronic infection with elevated IgG. could this itself cause

>plasma to expand?

Doubtful that the high Ig would cause blood/plasma volume to increase. There

may be some effect of the infection (like a toxin of some sort) that would

give this effect. The increase just isn't going to give a high enough

osmotic effect, without going way into pathogenicity first (the kind of

thing that B-cell lymphomas give.) An imbalance in ions, especially sodium

or chloride, would be more likely. A high albumin could also give this -

albumin is about 8 times more concentrated than Igs.

Otherwise I would suspect an autonomic nervous system disturbance - the same

kind of thing that gives most of us low blood volume.

>What do you mean by clotting factors ? - fibrinogen and things like that?

Exactly.

>My albumin was also high. Do you know what would cause that?

Don't know a cause - it could be genetic, but may also be a response to an

infection, or a response to autonomic dysfunction.

A high albumin level could lead to high blood volume. Albumin is used

therapeutically to draw fluid from tissues in certain cases of edema; going

overboard with that would lead to dehydrated tissue and high blood volume.

Jerry

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