Glossary

What this glossary is for

Rheumatology runs on a vocabulary that never gets explained to you first. You leave an appointment holding words like synovitis, seronegative, titer, and DMARD, and then you go and look them up. What you find is usually one of two things, either a dictionary line that tells you nothing useful or a page trying to sell you a supplement. This glossary covers the terms used across this site, written the way they're used in clinic.

Every entry gives the number behind a term where a number exists, which is a deliberate choice rather than a style. Saying a test is specific for a disease means one thing, while saying it's 95 percent specific means something rather different and a good deal more useful. Only the second one lets you weigh what a result means for you.

Where no number exists, the entry says so rather than borrowing one from a related measure or a different group of people. That comes up more often than you'd expect it to. An entry that says the evidence isn't there is more useful than one that fills the space with something borrowed.

The correction this page needed

The page this replaces said something that was wrong. It said about 5 percent of healthy people have a positive antinuclear antibody test, and that figure is right at one dilution only. As a general statement it misleads, and the difference is worth knowing because it changes what a positive result means.

An ANA test is done at rising dilutions of the blood sample, and the result is the highest dilution at which the antibodies still appear. One study gets cited most often here, and in it the rate fell steeply as the dilution rose among apparently healthy people. It was 31.7 percent at 1 to 40, 13.3 percent at 1 to 80, 5.0 percent at 1 to 160, and 3.3 percent at 1 to 320. The rate didn't differ much across age groups from 20 to 60.

So the 5 percent figure describes healthy people at 1 to 160, and quoted without its dilution it makes a positive result sound rare. That makes it sound far more alarming than it is, because many laboratories report at those higher dilutions. One US survey tested at a single 1 to 80 dilution and found 13.8 percent of people aged 12 and over positive, with the true value somewhere from 12.2 to 15.5. Women came out at 17.8 percent and men at 9.6 percent.

What a positive result turns out to mean

The reassuring number comes from following positive people forward rather than from testing them once. One study looked at 825 blood donors, of whom 130 tested positive by at least one method, which is 15.8 percent. Two of the 825 went on to a diagnosis of an autoimmune rheumatic disease over five years, and a rheumatologist made both of those diagnoses.

That study examined only 37 of the 130 positive donors, so it isn't a full account of what happened to all of them. The direction is clear all the same, and it's the direction anyone newly told their ANA is positive most needs to hear. A positive ANA with no symptoms alongside it is usually not the start of a disease.

The full performance figures sit elsewhere, on the lab reference page for antinuclear antibodies. That page covers what happens to positive results once they reach rheumatology. This page holds the correction because this is where the wrong number was, and fixing it on the lab page alone would have left it standing here.

How the entries are organized

The terms below fall into four rough groups. Drugs and drug classes cover what gets prescribed, and that group holds methotrexate, hydroxychloroquine, prednisone, the DMARDs, and the biologics. Lab and immune system words cover results and mechanisms, and that group holds rheumatoid factor, cytokines, TNF-alpha, interleukin 6, autoantibody, and HLA-B27.

Clinical findings cover what a doctor sees or a scan shows, and that group holds synovitis, uveitis, sicca, interstitial lung disease, pulmonary hypertension, and nailfold capillaroscopy. Disease state words cover inflammation, remission, and flare. Those three get used loosely outside clinic and strictly inside it, which causes more confusion between patients and clinicians than any of the technical words do.

A few entries fall outside those four groups because they belong to particular conditions. Those are antisynthetase syndrome, amyopathic dermatomyositis, immune-mediated necrotizing myopathy, and the anti-Jo-1 antibody. Insulin resistance and endocrine-disrupting chemicals are here for a different reason, which is that they come up again and again in the metabolic and environmental material, and both are widely misused in health writing.

Questions patients ask.