Other labs that you wanna pay attention to in connective tissue disease.
Rheumatoid factor could be seen in RA; maybe Hepatitis C.
What is rheumatoid factor?
Here we go.
So what happens with rheumatoid factor
is that the IgM is then going to target the Fc portion of the IgG.
Once again, I repeat, the IgM is going to then target
the Fc portion or region of the IgG.
That is the definition of rheumatoid factor,
and if I’m rheumatoid factor then it’s should be thinking rheumatoid arthritis.
Remember, we talked about the whole sleuth
of seronegative spondyloarthropathies, remember?
And there we talked about psoriatic arthritis,
we talked about ankylosing spondylitis,
inflammatory bowel diseases, psoriatic arthritis, and those are seronegative.
What does that mean?
These are RF positive.
Extremely important and much more specific for rheumatoid arthritis is this,
and please know this well, it’s called Cyclic Citrullinated Peptide (CCP).
Once again, cyclic citrullinated peptide, it is an arginine derivative.
There is another one called vimentin, but I’ll leave that alone.
The big one here is CCP, note well for rheumatoid arthritis, quite specific.
Now C-reactive protein is extremely non-specific.
Any type of inflammatory process, right?
For example, fever, inflammation, even the coronary arterial disease
will result in C-reactive protein to be elevated.
What is it?
It is an acute phase reactant.
All acute phase reactants are being synthesized from where?
The liver, good.
Do you remember the name of the interleukin that we discussed?
Keep that in mind.
So this, obviously, is going to be completely dependent on the level of inflammation.
ESR, Erythrocyte Sedimentation Rate.
So think of your RBC is being centrifuged,
higher the number the higher level acute phase reactant, especially fibrinogen.
Remember, these are the components coming from where?
And what is C-reactive protein usually refer
or acute phase reactant usually in response to?
Now, acute phase reactants coat the RBCs.
Next, and then decreases the forces keeping them apart
so the repelling force is then lost. Hah!
So if you then lose the repelling force of an RBC,
guess what they’re gonna do?
Stack up on top of each other like poker chips.
You like going gambling?
Here you go, here’s your rouleaux formation.
Here’s the actual physics behind it.
The false elevation can be seen with severe anemia
and then you can find a false decrease in liver disease is a big one.
Also nephrotic syndrome because you’re losing a lot of that protein,
aren’t you, in nephrotic?
In other words, take a look at these protein-losing enteropathies.
Have you heard of something called Menetrier’s disease, haven’t you?
So when you lose your protein you’re gonna have a false decrease of what?
Erythrocyte sedimentation rate.
You have a false elevation when you have severe anemia.
Keep that in mind.
Obviously, ESR is going to be non-specific, but you can use ESR.
For example, if you have a 67-year-old lady
and she complains a pain here in the temporal region
and you find an increase in ESR, the number one differential please?
Aha! Giant cell arteritis aka temporal arteritis.
Here we’ll take a look at erythrocyte sedimentation rate.
Think of doing a centrifuge on an RBC and what are they doing?
They’re coming together, sedimentation.
The higher the number is a higher level of acute phase reactants, for example, fibrinogen.
I told you acute phase reactants are being synthesized from where please?
Now what about these acute phase reactants?
What do they do?
The repulsive forces such as me—no, I’m joking—
the repulsive forces when they decrease between RBCs,
guess what they wanna do?
They wanna come together and stack up on top of each other
and you wanna go gambling—
no you don’t, not really, not in the state, but you form rouleaux formation.
That’s rouleaux formation, more number of acute phase reactant
you lose the forces repelling the RBCs.
Well, obviously, rouleaux formation is extremely nonspecific.
You can find rouleaux formation with multiple myeloma;
you can find it with Waldenstrom macroglobulinemia.
Now about that ESR, you can have a false elevation on your severe anemia
or you can have a false decrease in—
now you may give me the common theme—
you can have a false decrease in ESR in the pathology
in which the protein is either not being synthesized—
give me the disease there—organ liver disease or excessive loss.
Give me a kidney issue there,
nephrotic syndrome or you’re not absorbing the protein.
For example, you’ve heard of Menetrier disease.
Menetrier, too much mucus in your stomach, increase in the pH,
cannot cleave off the ogen off of pepsinogen
resulting in protein-losing enteropathy.
Whenever you have a condition in which you’re not able to properly supply
enough protein to the body in the serum,
you’re gonna have a false decrease in your erythrocyte sedimentation rate.