A #tweetorial on ANA, for non-immunologists.
As a medical student, I was taught ANA = lupus.
As a resident, I was taught ANA = red herring.
As a fellow, I have learned ANA can mean nothing or something, but if you miss the something, it could be bad.
So what is that something?

2/ ANA stands for “anti-nuclear antibody”. This just means an antibody against anything in the nucleus! It is not specific, as there are many things in the nucleus, things I’d long forgotten resided there.

3/ Things like dsDNA (SLE), histones (drug-ind SLE), centromeres and topoisomerases (scleroderma), ribonucleoproteins (MCTD), RNA polymerases (remember those?!), and so much more!

4/ When we test for ANA, we often to do this using immunofluorescence with HEp-2 cells (human epithelial cells that we found in laryngeal carcinoma and thought “Hey! These have big structures and high cell division rates so they’ll be great to use for ANA testing!” #science).

5/ So we make a layer of these HEp-2 cells and we dump our blood sample on them and if we have antibodies to the stuff in these cells, we’ll see them light up! They don’t always light up the same way, however, different antibodies are associated with different patterns of IF.

6/ Remember, ANA is not specific, it just means an antibody against SOMETHING in the nucleus, so these patterns matter. dsDNA may have a homogenous pattern bc it’s all up in the chromatin. U1-RNP may have a speckled pattern bc it’s in the nucleus but not the chromatin, and so on.

7/ But then what the heck is this result: “ANA negative, but cytoplasmic stain positive” that comes up in the order comments?! Confusing at first, but simple once I remembered what a cell was. Outside of the nucleus is the cytoplasm right? (Duh!)

8/ So if the blood you’re dropping onto these cells has antibodies to anything in the cytoplasm, then that’s where you’re gonna see it light up! Once I realized this, the name "ANA" testing seemed a bit of a misnomer, as the cytoplasm is clearly tested as well, but I digress.

9/ Things that are in the cytoplasm include, t-RNA synthetases (anti-Jo and more), mitochondria (like in PBC), and a host of other random enzymes and proteins that can be associated with disease (esp in myositis/dermatomyositis/ILD, we have found).

10/ SO, when you order an ANA (and please do this wisely), remember what you’re doing. Basically just dumping your patient’s blood on some cells that have all the things of a cell and seeing if any antibodies stick anywhere.

11/ Sounds wackadoodle, but in the right clinical context and with appropriate interpretation, it may be the first clue on your way to a diagnosis! For more information, check out the Atlas of Antinuclear Antibodies. Enjoy!
https://www.mblbio.com/e/ivd/atlas_structure.html