Rapid test strep VS mono... or both?

[db_pavnp]

For example, PPV of 70% means of 10 positive rapid tests, only 7 truly have the disease.

 

It's even worse than that as it doesn't take into account normal flora rates.  It doesn't test presence or absence of disease, only antigen or whatever other component a facility "RSS" buys.

 

I'm debating back tracking on this statement as PPV is a function of Sens / Spec plus disease prevalence.  Quindel brand RSS PPV can only be 70% (as you have quoted) in a specific patient population with a defined disease prevalence.  If that PPV is "all humans" than the true PPV in kids is higher and the true PPV in adults is lower.  If that PPV is kids, than the PPV for adults is much lower.  If that PPV is adults (surely not), then the PPV for kids is much higher.

[GetMeOuttaThisMess]

Ask and you shall receive. Adult sensitivity is 59%. Adult PPV is 70%, as is the peds sensitivity. Your statement regarding disease prevalence explains why sensitivity is increased in the same test at a different time of the year. Example: influenza sensitivity is greater in winter than summer due to increased prevalence of disease in community during that time.

[chichamorada]

Student here. Let me know if my logic seems ok:

 

For this child it seems appropriate to treat with antibiotics.  She had a high enough Centaur score even with non-tender lymph nodes that doing a rapid test was worth it (pos predictive value higher since pre-test probability already high).  If GAS were less likely, then would have sent throat culture and omit the rapid test.  Probably would have sent her home without abx in that case. 

 

From what I've learned, throat culture is important: (1) rapid strep test can miss 30% of GAS pharyngitis, (2) if the culture is positive for another type of Strep (e.g Group C or G) then you can shorten the course of abx to 5 days since no concern of RF for these bugs, (3) if cx is negative, at least you can be fairly sure it was not a streptococcus species (since cx is 90% sensitive), and the next time she gets a sore throat you know she's probably not a carrier.

 

As far as Fusobacterium is concerned, it seems you cannot rule this out with cx anyway.

 

MonoSpot likely would have been negative anyway since she had only been symptomatic for 2 days...not sure about whether it was worth doing?

And Mono will reveal itself in a few days with a rash and such.

[ventana]

Anyone have any comments on using AMOX as an ABX when you are looking at the DDX of Mono versus strep?

 

 

Is a very cool fact, that will help a HUGE amount but could cause a great amount of alarm if you do not know it.....

[GetMeOuttaThisMess]

Fusobacterium won't show up on a RST so it cannot be excluded in office at time of visit.  By the time the patient gets in to see you (let's say 24 hours), you do the culture, and you get the results back the pt. is already halfway through the illness.  You add abx. to the equation and it'll take arguably 48 hours to show benefit which now puts you five days out.  Here's the million dollar question.  How long does a run of the mill infectious pharyngitis/tonsillitis last?

 

Here's a second question?  Why do you even bother to treat GAS (don't throw out the generic answer about RF/PSGN and why wouldn't you)?

 

Let me ask a third question.  You are suspicious for strep but do a mono test, and lets even be more specific and get IgG/IgM titers for EBV (I always throw in CMV as well, or did in years past).  Your IgM comes back elevated and your IgG is normal but your culture also shows GAS.  What do you do (answer is not the obvious one which then begs the question "Why not?")?

 

What are some unique oropharyngeal findings on examination specific to mono?  Have you looked at the eyes, and if so, what are you looking for?

 

If mono is in my mind I automatically convert to cephalexin 500 mg. b.i.d. to avoid the amoxicillin interaction.  You could go PCN VK but that is such a pain to dose around because of the breakdown from gastric acid with eating.  Heaven only knows the number of folks mislabeled as PCN allergic as a result of a missed dx..  This begs the question of what's different with a straight forward mono rash and a PCN allergy rash?