Name:
S2D: The Symptom to Diagnosis Podcast - Episode 28: Sore Throat
Description:
S2D: The Symptom to Diagnosis Podcast - Episode 28: Sore Throat
Thumbnail URL:
/images/podcast-microphone-banner.jpg
Duration:
T00H28M20S
Embed URL:
https://stream.cadmore.media/player/169a7532-7b3f-42ae-8dfe-6c288c61fc26
Content URL:
https://cadmoreoriginalmedia.blob.core.windows.net/169a7532-7b3f-42ae-8dfe-6c288c61fc26/Stern S2D- Ep 28.mp3?sv=2019-02-02&sr=c&sig=G7cYQIp%2BbkA%2Fh0oYeM8pAgDJMpIY5UGM%2B9vTpJWQpwk%3D&st=2024-05-02T21%3A02%3A45Z&se=2024-05-02T23%3A07%3A45Z&sp=r
Upload Date:
2023-06-03T00:00:00.0000000
Transcript:
Language: EN.
Segment:0 .
[upbeat intro music] [upbeat intro music] [upbeat intro music] [Dr. Cifu] I'm Adam Cifu. [Dr. Stern] And I'm Scott Stern. [Dr. Cifu] And we're here with another episode of S2D, the Symptom to Diagnosis podcast. This podcast teaches evidence-based strategies for diagnosing common medical symptoms.
We begin each episode with a case unknown to one of us. We then discuss five high yield features that help to accurately diagnose the cause of the symptom at hand. We then return to our case before finishing up with a discussion of fingerprints, common misconceptions, pet peeves, and other random pearls of knowledge. The cases that we discuss are drawn from our clinical experiences but because protecting patient privacy is part of our oath, we never discuss actual patients.
What are we talking about today, Scott? [Dr. Stern] Well, today our topic's a pretty common topic and it's sore throat, and just like in our Symptom to Diagnosis textbook, we're going to focus on acute sore throat. And Adam, you are the expert of the day. And I was wondering if you had a case? [Dr. Cifu] I do, in fact. [Dr. Stern] Funny how that works. Go ahead.
[Dr. Cifu] So this is a 24-year-old medical student, he's been feeling poorly for about three or four days. He just says, "Ugh, you know, I'm tired, wiped out, some chills," and you'll never guess, a sore throat. [Dr. Stern] A sore throat, okay. [Dr. Cifu] He finally drags himself to student health and he's seen. There he's told he has a low grade fever, 99 degrees.
He's also told that he has enlarged tonsils that are a little bit erythematous, but no exudate. There's no cervical lymphadenopathy on the exam, and so he's told that he probably has a virus, and he's sent home with Tylenol and lozenges. [chuckles] I think that's all I'm going to give you. [Dr. Stern] Well, that's okay, I think that's plenty. - [Dr. Cifu] Okay. - [Dr. Stern] You know, so what do I think about with acute sore throat?
There's a couple of things that are just really, really common that we see all the time and are worth talking about. So probably the most common is just viruses NOS but there's a bunch of things we have to look for, including strep pharyngitis, mononucleosis, acute HIV infection, flu, and these days, COVID as well. acute HIV infection, flu, and these days, COVID as well. So those would be kind of pretty high on my list that I might think about actually testing for.
[Dr. Cifu] Sounds great. It's interesting, I think the only time that coronavirus appears in the last edition of Symptom to Diagnosis is on the differential for viral sore throat. [Dr. Stern] That's funny. [Dr. Cifu] So at this point, I don't know, would you critique the student care he received? Or are you sort of okay with this? [Dr. Stern] Well, I mean, realistically, he doesn't sound very sick.
He doesn't have exudate, you could argue about this "fever," if you really thought he had fever, it would be reasonable to do a rapid strep test to decide about whether or not to treat him. His symptoms are very short, and he doesn't have any cervical lymphadenopathy, so mono is not terribly likely. You wouldn't want to miss acute HIV, you wouldn't want to miss COVID, and he's going to be talking with other patients, which means he's putting them at risk for flu.
So I would probably be more aggressive with him, both because he's been exposed to people and also because he's going to expose others. [Dr. Cifu] Okay. [Dr. Stern] But that's also my style, as you said in recent podcasts, I'm the maximalist and you're the minimalist. - So I would- - [Dr. Cifu] Okay. [Dr. Stern] I would test him.
[Dr. Cifu] So you'd probably get a little bit more history it sounds like and a little bit more sort of post visit counseling also as far as making sure he's not putting other people at risk. [Dr. Stern] And I'd swab him. [Dr. Cifu] Yeah, right, and certainly these days you might COVID test him also given that this is clearly someone who's going to be exposed.
[Dr. Stern] Absolutely. [Dr. Cifu] This was in the distant past, shall we say- - [Dr. Stern] Ah, okay. - [Dr. Cifu] -not now. Okay, let's stop there. [Dr. Stern chuckles] So I think given all that, would you want to give us five points of what I should have done and then we can go back to the case so you can fix it? [Dr. Cifu] Sure. No, I think you managed him just as they did. Okay, so my five key points, I'm going to start with differential diagnosis.
I seem to always start with differential diagnosis, just kind of the framework. And the framework for sore throat is really viral causes, bacterial causes, and non-infectious causes, sort of like acute diarrhea actually, but let's move on from that. So viruses you can usually recognize because there are usually other symptoms.
So it's not just sore throat, there's often cough, coryza, rhinorrhea, myalgias, those kind of things. It sounds like a viral syndrome with sore throat being one of the many symptoms involved. Bacterial infections on the other hand, you know, sore throat is usually the primary dominant system, obviously, you know, these aren't perfect, but that's sort of a good thing to keep in mind.
And non-infectious causes, one, they don't have shockingly infectious symptoms, right? So you don't expect people to feel crappy, have fever, things like that, and because a non-infectious sore throat is usually due to some other condition, you usually have symptoms of that other condition. So for instance, if the person has a sore throat because of reflux disease, you know, they may have classic heartburn.
If it's wheezing cough, they've got a cough, if it's because of post-nasal drip, they probably got congestion and it's probably worse lying down and all that kind of stuff. So you can at least kind of organize your thinking in those three big pivotal points as you go into a patient. [Dr. Stern] So we would take out the third one for him, because he clearly sounds infectious, - and now we're looking at - [Dr. Cifu] Right.
bacterial or viral primarily. [Dr. Cifu] Totally, totally. [Dr. Stern] Alright, you have second point? [Dr. Cifu] Second key point, this is kind of a weird one on this podcast that we're like all about diagnosis, right? But you have to keep in mind why it is important to make a diagnosis. And that's because so many of the sore throats that you see are, as you said, you know, virus NOS, doesn't need any specific treatment, it's going to get better on its own, there's a tendency to get lazy.
And so I think to keep you from getting lazy, you have to think about like, why would I need to diagnosis this person with something? And the complications you want to think about are suppurative complications, right? So, you know, pusy complications, so, you know, peritonsillar abscess, right? Like bad things like that. There are the non-suppurative complications, and those are like the classics, you know, acute rheumatic fever, post-strep glomerulonephritis.
There are infections that actually may require either specialized treatment or counseling, and you mentioned some of these, right? EBV, GC, HIV, fusobacterium, right? Just a disaster, it needs to be treated. And then the primary cause that I talked about before, you know, is there something else which is causing this? So a sore throat isn't going to get better if it's related to GERD unless you do something to treat the GERD, right?
Which might be non-pharmacologic, might be pharmacologic, whatever. [Dr. Stern] Who gets fusobacterium? I've never seen that. [Dr. Cifu] We'll get into that. [Dr. Stern] Okay. And do you know in Australia they call a peritonsillar abscess a quinsy? [Dr. Cifu] Yes. [Dr. Stern] Where is that term from? [Dr. Cifu] I saw it as like an old medical term and not as an Australian term.
[Dr. Stern] Oh, I just know because one of my relatives once was in Australia had called me up and says, "I have a quinsy-" - [Dr. Cifu] I have a quinsy. - [Dr. Stern] And I'm like- -what the hell is a quinsy? [chuckles] [Dr. Cifu] The Australians have funny names - for a lot of things. - [Dr. Stern] I guess. [Dr. Cifu] I listen to a podcast called the Unmade podcast, which is these two Australian guys talking, and they're funny because they often point out things, and one of the things that always comes up is documentaries they refer to as docos.
[Dr. Stern] Docos. Wait, they call their podcast the Unmade podcast, but they made the podcast. [Dr. Cifu] Oh, it's spectacular. So the entire podcast is ideas for podcasts which will never be made or which at least - they won't make. - [Dr. Stern] Oh my god. - That's funny. - [Dr. Cifu] Oh it's so good. [Dr. Stern] All right.
So you've told us now what the differential was and the second one was why we need to worry about some of those entities. What's your third key point? [Dr. Cifu] Third key point, the center score. - Okay? - [Dr. Stern] Ah. [Dr. Cifu] Because who doesn't love a really good clinical decision rule, right? And if you think about clinical decision rules, like the very first two things that should come to mind are the center score for strep throat and the Ottawa Ankle Rules, right? They're like, when you teach clinical decision rules, that's how you need to teach them.
So what is in the center score? So it's made up of five things. So the presence of exudates, the presence of cervical lymphadenopathy, the presence of fever, the absence of cough, and age under 15, and all of these things are factors which increase your likelihood of having strep throat, okay? And if you have four or more of those findings, that has a likelihood ratio of about five and most of the charts which deal with this say, okay, so let's actually use that likelihood ratio.
And if you're in kind of a regular, you know, adult urgent care place, the background likelihood, kind of just prevalence of strep throat among people coming in with pharyngitis is about 10%, that's like your pre-test probability. So with a likelihood ratio of five, if you have four or more positive, that comes up to be 35% post-test probability.
And so we usually think like that's certainly enough to test, right? And so that's often used as a cut point for should we do a rapid strep test or not? [Dr. Stern] So he had no cough presumably, at least you didn't mention it. [Dr. Cifu] Right. [Dr. Stern] And we could say he had a fever, although it's low grade, but probably real.
[Dr. Cifu] Right. [Dr. Stern] So he would get two, right? [Dr. Cifu] Exactly. I did the calculations. So two would get him to a post-test probability of about 10%. Three, because I'll tell you an interesting thing that happened in this case, three gets you to a post-test probability of 22%. [Dr. Stern] You know what I don't like about the center score is, it equates all those as being the same, and my clinical experience would say that exudates weigh heavier than some of the others.
Do you have any data on that? You're laughing at me. [Dr. Cifu] You're such a snoot. You're like pulling out your anecdotes - from 50 years ago. - [Dr. Stern] I am! I am! But tell me that's not true! [Dr. Cifu] Come on. It's a well validated clinical decision rule. - I'm sure- - [Dr. Stern] Right. [Dr. Cifu] -it's better validated than your made up - clinical acumen [chuckles]. - [Dr. Stern] Fine, fine.
Those are fighting words. All right. [Dr. Cifu] Clinical acumen with quotations - around it. - [Dr. Stern] Oh my goodness, we're going to break into a fight on this podcast. All right. So the center score. What's your fourth key point? [Dr. Cifu] Okay. So actually four and five, I'm going to concentrate on two must-not-miss-diagnoses. And I think you actually, well, you mentioned one, and I'm going to mention another one.
So first is Lemierre's syndrome which is caused predominantly by fusobacterium, and come on, fusobacterium necrophorum, could you come up with a scarier bacterium name? [Dr. Stern] Dead man's disease. [Dr. Cifu] So Lemierre's syndrome is a septic thrombophlebitis of the internal jugular vein, okay? It's usually proceeded by pharyngitis and then patients present with high fevers, rigors, neck and throat pain.
And it can be a disaster because as you imagine, you know, if you have a septic thrombophlebitis of the IJ, you generally get septic emboli, there are local complications, it's kind of a disaster. It needs to be recognized. It needs to be treated. So this is another reason that when you see a person, you know, with a sore throat, do a careful neck exam. See, you know, are they actually tender over their IJ?
Because someone who's got strep throat, you know, they may have tender nodes, but they're not going to have tenderness over their IJ. And if patients are coming in with a sore throat and have things like say dyspnea or pleuritic chest pain or abdominal pain, you should really broaden your differential and think about fusobacterium. My fifth key point you definitely mentioned is acute HIV.
So acute HIV is much less common than it used to be, but obviously people are still getting HIV, and somewhere between 50 and 90% of people have an acute retroviral syndrome after they're infected. So it's important to recognize this. And probably the reason that it's most important to recognize it is that during the acute retroviral syndrome, people have a very high viral load, and almost by definition, right?
They don't know that they have HIV during that time. So if they're feeling well enough, they may very well be sexually active. And so then it's not just your patient you're taking care of, it's contacts of the patient who you're taking care of. The presentation is mostly non-specific, which I guess means that we have to be thoughtful about it. Two things that you can see with acute HIV, acute retroviral syndrome, that's less common with other things are rash, see that in an over 50% of people, and mucocutaneous ulcers, which actually are pretty specific, but not very sensitive.
[Dr. Stern] Interesting. You know another one we didn't mention which I thought about when you were talking about examining the neck is every now and then acute thyroiditis. [Dr. Cifu] Yeah. [Dr. Stern] It's really neck pain rather than sore throat, but I've had patients come in and say they have a sore throat. And only when you ask them to point to where it hurts, they point to their thyroid, right?
Have you seen this too? [Dr. Cifu] I'm like stop talking, because that's one of my clinical pearls. [Dr. Stern] Oh sorry, I'm going to stop talking. [Dr. Cifu] We clearly don't have as much to talk about with sore throat because we're sort of like- [Dr. Stern] Riffing a bit much. [Dr. Cifu] Exactly, and trying to stay away from some things that are coming up later.
[Dr. Stern] All right. So with all of that, we've got a guy with a sore throat and a center score of two out of five. And I was recommending doing a nasal swab for COVID, which will give us flu, and a throat swab for strep, whether or not I test him for mono now, or wait for a couple of days- - [Dr. Cifu] Right. - [Dr. Stern] -I might wait, but I could certainly see checking an acute HIV test.
So back to the case. [Dr. Cifu] So he comes back and his roommate who's, you know, learning clinical skills, and his roommate who's, you know, learning clinical skills, examines him and says, "I think you have lymphadenopathy. I think you have tender cervical nodes." And then roommate of the medical student, who's also a medical student and medical student shrug and, you know, move on with their lives.
[Dr. Stern chuckles] [Dr. Cifu] Our patient just gets worse and worse over the next two days. Two days later, he wakes up absolutely rigoring, drenched in sweat, miserable. Roommate takes him to the emergency room because it's Sunday morning at this point. And he's got a huge peritonsillar abscess - actually at this point. - [Dr. Stern] Oh my god.
[Dr. Cifu] And it's such an interesting story, as you can tell, this is a little bit more real than many of our stories, because the emergency room doctor just did an I&D right there, and as the pus was evacuated from this abscess, our patient was like, "Huh, I feel all better." [Dr. Stern] Oh my god. [Dr. Cifu] It was the most striking cure I've ever seen.
[Dr. Stern] Just the thought of having your throat lanced - and pus dripping out- - [Dr. Cifu] I know, I know. [Dr. Stern] -is disgusting. [Dr. Cifu] Well, so that's the case. [Dr. Stern chuckles] All right. So now that we're done with that, we're going to go to fingerprints, misconceptions, pet peeves, et cetera. So fingerprints, what do you got? [Dr. Cifu] I got nothing. How about you?
- [Dr. Stern] I got nothing. - [Dr. Cifu] Yeah, okay. - Common misconceptions. - [Dr. Stern] All right. - Go ahead. - [Dr. Cifu] I'll start out. So the common misconception is kind of the need for throat cultures, and this is to really understand your rapid strep test, your RADT, your rapid antigen detection test. So the sensitivity and specificity of that test, sensitivity 70 to 90%, 90% is kind of what's on the package, 70% is what comes up more in kind of clinical studies, because there's obviously a lot of user variability, right?
If you like poke the tonsil, that's one thing. If you miss the tonsil completely, that's another thing. And if you really get in there and swab up and down until the person gags, that's another thing. So sensitivity 70 to 90%. Specificity is really good, 90 to 100%. Thus, if positive, there's really no reason to send a throat culture, right?
It's positive. You're going to treat, the specificity is high, you know, you're done. If on the other hand, it's negative, in a low-risk person, who's at low risk for complications, basically adults, right? There's really no reason to send a culture. If it's negative in a high-risk person, maybe a child, an adolescent, maybe some child or adolescent with, you know, exposure history, something like that, then it really makes sense to culture so you've got backup given the lowish sensitivity.
[Dr. Stern] So with those, if you rewind not knowing he developed a peritonsillar abscess, with just a low grade fever and the erythematous throat before he has lymphadnopothy, would you have done a rapid strap on him when he was first seen? - [Dr. Cifu] Totally. - [Dr. Stern] Totally. [Dr. Cifu] And I think you would have done the same thing. [Dr. Stern] Well, you know me.
[Dr. Cifu] Right, I mean, you probably would have biopsied his tonsils. [Dr. Stern] Right, you know, I'd probably have done a chest X-ray and a head CT scan just to make sure. - [Dr. Stern] All right. - [Dr. Cifu chuckles] [Dr. Cifu] How about you? You have any common misconceptions? [Dr. Stern] Well, just that you've already mentioned that it's all viral, I do think we tend to get lazy. [Dr. Cifu] Yeah. That's a good point.
And you know, there are a lot of, I was going to say finding a needle in a haystack, but it's really not that, it's always being aware that there's the potential for something worrisome, right? And whether it's sore throat or headache, or I don't know, cough, you know, it's to simultaneously recognize that like, this is probably nothing, but it's something really important for the patient because the patient actually came in with this, right?
So I need to make sure that I'm doing a good job, that I'm reassuring the person appropriately, not excessively working up everybody, right? Because you don't want to scan every headache that comes in, but on the other hand, always recognizing there's some finite possibility that this is one of these can't-miss-diagnoses that I got to always be ready to evaluate. [Dr. Stern] Well on that we agree. How do you like that?
[both chuckle] [Dr. Cifu] It's got to happen sometimes. [Dr. Stern] All right, pet peeves. What do you got? [Dr. Cifu] Pet peeves. Okay. So mine are really nitpicky. So- [Dr. Stern] Go ahead. [Dr. Cifu] To our listeners, please try not to grind your teeth while I go through these. The first one is identifying things that are not lymph nodes as lymph nodes.
And I say this just because I've seen this done a lot by people who should know better, okay? So submandibular salivary glands. Everybody should stop, you know, take one hand off the steering wheel if you're driving and feel your submandibular salivary glands. We all have those, okay? Those are normal. Don't call those swollen lymph nodes. And the other thing that is funny that I've seen a lot of people say, "Oh, this is a swollen lymph node," is the carotid bulb, right?
And the clues to the carotid bulb is it's generally directly lateral to the superior border of the thyroid cartilage and, wait for this, it's pulsatile, assuming your patient is alive. And so you should not call that a lymph node as well. [Dr. Stern] Don't you worry then it's an aneurysm? [both chuckle] [Dr. Cifu] Let's go on. [Dr. Stern] All right, so my pet peeve is actually either people not using a tongue depressor or not being able to find one.
I mean, it's very- In many patients, you can't get a good look at the tonsils by just saying, "Ah." And there's so many times people are lazy, like, look at the tonsils. [Dr. Cifu] Right, right, right. You can't say the person doesn't have exudate if all you can see is tongue when people open their mouth. [Dr. Stern chuckles] Exactly.
[Dr. Cifu] The exam is amazing because, you know, I've had some people who I say, you know, "Open your mouth and say, ah," and I get a perfect view of their epiglottis. I feel like I can intubate them right there, right? On the other hand, there are people who, I mean, it's like a surgical procedure just to get a look at their tonsils. [Dr. Stern] No kidding.
[Dr. Cifu] Most of those people should probably get a sleep study as well - as a rapid strep test. - [Dr. Stern chuckles] True. [Dr. Cifu] Not knowing what my pharynx looks like, I'll say that. I have one other one, and this is as nitpicky, it's empiric therapy for group A beta-hemolytic strep it's empiric therapy for group A beta-hemolytic strep after negative rapid strep test, okay?
Now there might be a reason to do that, like if you have a really high pre-test probability and your strep test is negative, you should still treat, but in that case, why do the rapid strep test, right? You know you're going to treat irrespective of what the response is. I think the only time to do that is, you know, there are some people who it is really profoundly difficult to do the test.
And if you're like, "I'm going to do a rapid strep test," and you get in there and the person's gagging and pulling away from you and you get a bad sample as negative, then it makes sense to like use your clinical reasoning and say, "Listen, that's not going to affect my decision-making." [Dr. Stern] That makes sense. All right, pearls. [Dr. Cifu] Okay. This is the one you ruined.
[Dr. Stern] I'm sorry. [Dr. Cifu] It's like opening a Christmas present - before Christmas. - [Dr. Stern chuckles] [Dr. Cifu] Do a thyroid exam for anybody who comes in with a sore throat and the reasons are, a, if you do a thyroid exam every time a patient comes in with a sore throat, you get really good at your thyroid exams, because you feel, you know, hundreds of thyroids every year.
And then as you mentioned, occasionally what happens is you find out that it's not their throat or their cervical nodes that are tender, it's their thyroid. And right there, you're like, "Huh, how about that? This is thyroiditis." And the reason that you're feeling crummy and feel like you have a low grade fever is because you have thyroiditis.
And you know, you'll usually whatever, send a TSH, you know, send a CRP, make the diagnosis and treat them for thyroiditis and give them a little bit of a more accurate prognosis. [Dr. Stern] Well, that's great, and mine is actually, I've never seen any data about this, I suspect it's out there, but I've had so many people who've come in who have a child who has strep throat and they have a bit of a sore throat and you look and it looks completely benign and you're sure it's not strep and you culture them, and it's positive.
And so I've just gotten to the point now where if somebody has a documented family member who they live with who has strep throat and a sore throat, that I just treat them. What do you think of that? [Dr. Cifu chuckles] I like it. You're a little bit Dr. Anecdote today, but- [Dr. Stern] I'm sorry. What can I say? Dr. Anecdote?
[Dr. Cifu] I think the only thing I'd pull you back on is, you know, people get group A strep colonization, right? And so you should not be culturing the asymptomatic, you know, contacts of- - Nobody would do that. - [Dr. Stern] Fair enough. [Dr. Cifu] But if the person's there with a sore throat and you know, their sister has a sore throat, Jesus Christ. [Dr. Stern] Right, right, right. [Dr. Cifu] Probably don't even need them to come in.
[Dr. Stern] Right, just call it in. [Dr. Cifu] Okay, my clinical pearl is maybe obvious, maybe not. People with group A beta-hemolytic strep really should get better about, you know, within about 48 hours after starting antibiotics. And because we've talked a little bit about complications, right? We talked about peritonsillar abscess, and because we talked about fusobacterium, say, you're treating someone because you've got a high clinical suspicion of group A beta-hemolytic strep, you decide not to culture them, and then after two days of penicillin, they're like, "Doc, I'm worse." You know, there's something wrong there, that person needs to be seen.
You got another one? [Dr. Stern] I do. So you mentioned actually a rash earlier with acute HIV, but I would say when you have a patient who has a sore throat and a rash, there's a couple of things to think about. So first, strep throat can come with a very fine rash that's palpable, very, very tiny papules that are so small you really feel them more than see them on an erythematous base.
They say it feels like sandpaper, which it kind of does, and that's a classic scarlet fever- [Dr. Cifu] Yep. [Dr. Stern] -actually. So if you see that, that's very helpful. HIV can have an erythematous macular rash that's typically on the chest and on the upper extremities, so another one to think about. And if people have discrete pustules in different parts of their body and a sore throat, then you should think about GC.
So we definitely shouldn't ignore a rash that's present with a sore throat. [Dr. Cifu] Good. What about a rash after a course of amoxicillin - for a sore throat? - [Dr. Stern] Ah, thank you. Well, that's classic for mononucleosis. I almost forgot to mention that, so thanks for reminding me. [Dr. Cifu] I got to say I don't know what the data is on that but that's another one that we just like, you just accept that that's truth.
[Dr. Stern] Right. Right. [Dr. Cifu chuckles] Hopefully it is truth. [Dr. Stern] Right. Now, apparently it's a third, I read it's apparently a third of people who have mono who get amoxicillin- - [Dr. Cifu] Interesting. - [Dr. Stern] -get a rash. What's with that? I mean, it's so weird. [Dr. Cifu] You're the pathophysiology professor. [Dr. Stern chuckles] Well, okay.
Well, I don't know the answer to that. [Dr. Cifu] I'll add one thing just because it's in the joint pain chapter about the rash with disseminated GC. So there are two rashes actually, you know, there's one which is the one you mentioned, which are actual pustules that if you unroof them, there's GC, you know, inside of those, and then there's a much less specific rash, sort of a general macular rash that people can get.
So I've got one more clinical pearl. You ready for this one? [Dr. Stern] Sure. [Dr. Cifu] This goes back to HIV. Clearly, I think the two of us are maybe showing our age a little bit with all the HIV, but it is a really important "can't miss" here. It's just to remember the time course for acute HIV because this helps you if you're suspicious of getting the history and knowing what tests to do.
So the incubation period for HIV is one to four weeks. Meaning that if someone comes in with an acute retroviral syndrome, the exposure should be one to four weeks before, okay? And then as far as testing, so HIV antibodies which we usually use for diagnosis, those with the most modern antibody tests, those turn positive about 18 days after exposure. So if you go through the timing, it's really actually possible that you would see a person who's sick with an acute retroviral syndrome who's still got a negative antibody test.
On the other hand, the viral load is generally positive by about day 11. So just about everybody who you're seeing who's sick with HIV will have a positive viral load. And the positive viral loads are generally really high, like over 100,000. And so actually, you know, if you send a viral load, and your antibody is negative, and your viral load is low, like less than 10,000, you should actually keep an open mind, because that may actually be a false positive.
You got one more pearl, Scott? [Dr. Stern] I do. So every now and then you have someone whose sore throat's a minor part of their illness, and the first thing you realize is their LFTs are abnormal, and that can be a signal that the patient either has mono or acute HIV. The other thing about mono that's odd is the Monospot early on can be negative, especially when people are very sick, and so some of the clues can be abnormal LFTs or an atypical lymphocytosis on a CBC.
And sometimes you have to just keep repeating the Monospot or you could get an EBV DNA level if you wanted to, to make that diagnosis. [Dr. Cifu] Perfect, and so these are people who are a little bit more complicated who you're seeing, who you think this isn't strep, or maybe their rapid strep test is negative, you say, "I'm going to test this person a little bit further," and you'll say, "Okay, I'm going to do a CBC, I'm going to do a CMP, I'm going to do a Monospot, you know, maybe I'm doing HIV in this person." There was another test I was going to add, which I forgot what, you know, maybe you're going to do actually blood cultures if you're thinking about GC, because certainly the people who have what we call the triad presentation of GC, who are people who have the joint pain, the rash, fever, those people can actually have positive blood cultures as well.
[Dr. Stern] The other thing about mono is it really can cause a really remarkable exudative pharyngitis. So when I see someone and they have tons of exudates and it's not strep, boy, mono's the top of my list. [Dr. Cifu] Absolutely. Right. So, you know, exudative pharyngitis is strep or mono. [Dr. Stern] Right. That's been my total experience. [Dr. Cifu] Yeah. Right. I guess one could be confused by diphtheria.
[Dr. Stern] Right. [Dr. Cifu] We don't see it that much, but that's not really tonsillar, and you really shouldn't be seeing diphtheria. [Dr. Stern] I'm hoping not. [Dr. Cifu] We hope you found this episode of the Symptom to Diagnosis podcast useful and a bit enjoyable. As a reminder, our textbook, Symptom to Diagnosis An Evidence-Based Guide takes a much deeper dive into how to think about and reason through the diagnosis of medical presentations.
The book is available in print, on your handheld device, and in a fully searchable mode via the AccessMedicine website available worldwide for McGraw Hill. The music for this, the S2D podcast, is courtesy of Dr. Maylyn Martinez. [upbeat outro music] [upbeat outro music] [upbeat outro music]