An ongoing dialogue on HIV/AIDS, infectious diseases,
February 4th, 2026
Mystifying Abbreviations — Infectious Diseases Edition
Motivated by an attending stint on the general medical service, I once wrote a post here called, “Mystifying Abbreviations on Medical Rounds.” It proved to be quite popular, so I’m pleased to inform you that saying “RUQUS” (right upper quality ultrasound) and “G and G” (glucan and galactomannan) have truly entered the vernacular, especially here at my hospital.
(I’m convinced we remain the #1 utilizers of beta glucan testing in the world, for better and for worse. The low-risk case with the barely positive beta glucan triggers a spectacular number of unnecessary ID consults.)
Now, I’m back with a similar topic, only this time with an ID-specialty focus. My inspiration this time wasn’t the inpatient medical service, but an email a colleague wrote that truly stretched the limitations of my acronym knowledge. I found myself re-reading several sentences, wondering “huh?” and “what the …?” multiple times, not able to decipher their meaning even within the context of the email.
Here, for the record, is part of that email:
RCTs on provision of SUD tx with PrEP and ART like MHUs and PNs — RCT just completed NIDA funded, CROI abstract to come … also LAI PrEP and ART plus SUD tx to PWUD …
So here’s the challenge: I’ve listed a bunch of ID-related acronyms below and made brief comments that sometimes are hints — and other times are just the first thing that popped into my head. You, the wise readers, will offer your suggestions about what they mean. Some should be easy, some might be truly head-scratchers, but that’s part of the fun.
Have at it.
IGRA — frequently ordered, almost as frequently misinterpreted
PWID — very similar to PWUD, but somehow different enough to justify a separate acronym
BSI — not to be confused with BSA
CLABSI — BSI, but now with administrative consequences
CRBSI — similar to CLABSI, but until recently, I hadn’t heard this one so including it here
DILI — sounds cute; very much not
VRE — a three-letter word that can force you stop citalopram
CRE — looks like VRE, behaves worse
CPE — related to CRE, but more specific
ESBL — aspires to be pronounced as a word like MRSA instead of letter-by-letter, which it always is
PSSA — say this one it as it’s written and you too can sound like you’re from South Boston
LAI — add it to your coffee in the morning
MDR — vague, ominous, and highly contextual
XDR — MDR, but worse
RIPE — not for XDR
BCx — the lowercase “x” at the end is different from the X in XDR, and stands for … nothing, though UCx uses it too
PDR — RRRRRR, or “pirate bacteria”
SUD — encompasses OUD, AUD, and StUD — and you know what those are, right?
TDM — sounds straightforward until you need to interpret and act on the results
EHE — bold vision, weird acronym
IRIS — pretty name, not so pretty to manage
LTBI — may need RIPE “lite,” and importantly non-infectious
PsA — no one can explain why the third letter is capitalized
bNAbs — another one with inscrutable capitalization rules — I mean, why not BNAbs?
TOC — beware lingering molecules of dead bugs!
OPAT — does not refer to Irish people named “Patrick”
EOT — you’ll suffer if you don’t specify this for your OPAT patients, those named Patrick or otherwise
AYALHIV — well, I know what the last three letters stand for
Of course, abbreviations and acronyms exist for a reason — they save time, space, and keystrokes, and they let us sound efficient while we’re still figuring things out. But when they pile up unchecked, they turn even a straightforward clinical discussion into something that feels like a badly encrypted message, or that 6-character jumble (the confirmation code) that you get with every flight. People are well within their rights to say, on hearing a new one, what does that mean?
Before wrapping up, here’s one of the more absurd abbreviation sagas in modern medical history. For years, we’ve been required to check off “GC modifier” on every patient we see with a trainee in order to get credit for their documentation. Fine.
But no one — and I mean no one — knows what “GC” actually stands for. Not physicians. Not coders. Not compliance officers. It exists solely as two letters that must be clicked, lest the visit somehow not count. Which may be the purest example of an acronym achieving total bureaucratic independence from meaning — and a fitting way to end a discussion about how shorthand, once created, takes on a life of its own.
Paul E. Sax, MD
Associate Editor
NEJM Clinician
Biography | Disclosures & Summaries
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