Syphilis Lab Diagnosis for New NPs

Jan 12

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Show notes:

Syphilis lab interpretation can be confusing, and it’s a BIG topic, but in this video I review the most common scenario that I see in primary care.

Interpreting Syphilis Labs in Primary Care

I cover treponemal and non-treponemal tests, how to interpret them most specifically in the context of slightly abnormal, asymptomatic patients (the most common scenario in primary care), as well as the treatment and follow up, and when to refer to a specialist.

Lab Interpretation Crash Course

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0:00
well hey there it's liz rohr from real
0:01
world np and you're watching mp practice
0:03
made simple the weekly videos to help
0:05
save you time
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frustration and help you learn faster so
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you can take the best care of your
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patients
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so in this week's video i'm going to be
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talking about syphilis and i'm going to
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actually be talking about a very
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specific scenario that i see
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all the time in primary care so we look
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we learn about syphilis in school right
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and we learn about
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you know primary the secondary tertiary
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all that stuff um
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most of the time um when i am
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encountering syphilis and specifically
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i'm talking about like lab
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interpretation in this video
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so like when i specifically like the
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main scenario that i'm seeing is
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something to do with the labs being
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abnormal
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but they never had symptoms in the first
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place so i'm really going to focus on
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that touching a little bit on
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when patients are symptomatic and you're
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you're proactively concerned about them
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being
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having syphilis versus when you're
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screening them uh for whatever reason
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so uh i want to talk about the labs
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right so when it comes to diagnosing
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syphilis
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and you're doing a screening test and
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they whether or not they have symptoms i
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guess either way but
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uh if they have no symptoms sometimes
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you can get
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a positive test back right and then
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you're kind of left with like oh gosh i
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didn't expect that what do i do with it
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right
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so there's two main categories of tests
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there are the uh
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non-treponemal and the treponemal
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so non-treponemal are the screening
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tests that we usually start with
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um that are less complicated more cost
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effective we start there and if those
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are positive then it will kind of
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reflexively go to the treponemal tests
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so the non-treponemal tests are
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typically rpr
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i can't remember it off the top my notes
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are a little convoluted but
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rpr and vdrl are the two main ones sorry
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about that
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and then um if when that is reported
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back it's actually a dilution
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so without getting into the too much of
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the details it's basically like a ratio
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of like how much they had to dilute it
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to how much was
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detected right so the ratio is 1 to 2
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1 to 4 32 64 120
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like it keeps going up and up thousand
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two thousand right and the higher
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the second number the more likely it is
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to be an acute infection
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versus a false positive versus a latent
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infection right so the rpr is usually
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the one that
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our lab does i'm more familiar with that
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so the rpr for example is positive is
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rea it will be either non-reactive or it
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will be reactive and then it has a titer
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associated with an antibody titer in
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that one to whatever ratio
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and so when that becomes positive the
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workflow is typically
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that the laboratory you're ordering from
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will add on the treponemal test
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automatically and the department of
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public health will likely be notified
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that's how at least it works in
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the state i live which is massachusetts
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i would check with your supervisor on
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that but that's the general like
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workflow of what happens and so you
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automatically get a test added on
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or they call you and they ask you to add
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it on that kind of thing so the the
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treponemal test the more specific a
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little bit more complicated tests
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there's a whole bunch of them and i have
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my notes here so i don't forget um fta
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abs fda antibody that is like the main
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one that i see
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fluorescent treponemal antibody
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absorption um there's a whole bunch of
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other ones
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i'm not as familiar with mhatp tppa i
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have seen that one
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t-p-e-i-a so those are um treponemal
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palladium particle agglutination assay
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and t-palladium enzyme immunoassay
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and i guess what i've read that the
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tpeia
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is recommended but most of the time like
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i said i see the fta antibody but
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basically it's like
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a confirmatory test any of those will
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come back as
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as like reactive or not reactive or
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positive or negative
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and once those are positive they will be
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positive for life so that doesn't
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necessarily tell you if it's an active
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infection right now
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it just suggests very sensitively and
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specifically
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that it is likely an infection at some
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point right
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and so where you go from there depends
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on a couple of different things so
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one if you have a positive rpr and a
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positive fta abs or whatever it is the
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trumpet email test of your choice or of
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your lab's choice
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if those are both like positive there
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are some rare cases of them being both
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false positive but that's pretty
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uncommon the more likely scenario is
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that the rpr is going to be false
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positive and then the fta abs
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or the whatever the treponemal test is
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going to be
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negative which is suggestive of a false
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positive and the reasons behind
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that are a little bit obscure to me but
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they're not very common they can be like
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a reactive thing i've seen it in some
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people with
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um like autoimmune conditions stuff like
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that but um when it comes to the actual
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interpretation if you have both the
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positive rpr that has a titer
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and then you have the positive antibody
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of some kind or the treponemal test of
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some kind
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you can take it from there and so the
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places that you take it from there
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are do they have did they have symptoms
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at the time of presentation right and
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i'm not only briefly touched on that
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because it's a little bit more involved
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and i think we got a little bit more of
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that in school honestly versus like this
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kind of
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other scenario which is like you kind of
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just have to figure out
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but yeah so um for the symptomatic
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patients um it's important to
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investigate like
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what are we dealing with here right like
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it's a secondary tertiary what were the
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initial presenting symptoms do they need
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to see infectious disease like i would i
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would tag in somebody if i
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found that to be the case and then the
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second kind of scenario is like did they
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um you know if they have no symptoms
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then kind of like where
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are we from there right and then that's
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kind of getting into the history right
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because
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it doesn't necessarily mean that they
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have an infection now but they have at
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some point
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and i say that for a couple reasons just
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stick with me for a second but the main
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thing you want to ask
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is if they have no symptoms did they do
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you have any records or do they have any
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history of treatment because what can
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happen
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is that they expected actions after that
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happens for example say if somebody has
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a one to four
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titer on their rpr and they have a
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positive fta antibody and they have no
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idea if they've ever been treated before
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and basically
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you're getting into what type of
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syphilis are we talking about
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you have to presume that if they don't
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know if it's been treated that you have
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to presume that it's never been treated
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and then if you can try to compare to
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their previous labs is this from the
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last 12 months
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or is it just unknown completely and i
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have to say the most common scenario is
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unknown completely
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no records no idea about treatment that
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whole thing so yeah so doing your best
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to elicit if it's in the last 12 months
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or not because that kind of helps to
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differentiate what type of syphilis
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we're talking about if it's latent
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syphilis or if it's late late in
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syphilis and late late in syphilis is
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like
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you have no idea it's greater than 12
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months since they possibly got that
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infection
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and they have no symptoms right that's
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the key here if they have any symptoms
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i'm definitely consulting with either id
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or my supervisor
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and like doing more digging and research
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right it just doesn't come up that often
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um but for those people who are
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asymptomatic well someone with an rpr
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one to four
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positive antibody no history on record
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no idea if they've ever been treated no
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idea if it happened in the last 12
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months
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we're assuming that it's a late latent
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syphilis and then we're going to
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treat them as such and so the main
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treatment is um
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uh bicillin pen uh penicillin g i'm not
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going to say it right
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but is a brand name i'm not affiliated
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with them
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uh 2.4 million units i am once a week
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for three weeks and we just have to
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presume i mean there are alternatives if
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there's a penicillin allergy of course
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but that's like the main treatment and
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then what your follow-up monitoring is
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and i have my notes here that's why i'm
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looking over there
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the main thing for follow up is you're
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checking their labs again
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the rpr again the fta antibody or
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whatever treponemal test you've already
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done
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is going to stay positive but the rpr
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theoretically
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will decrease fourfold like four times
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below to show that it's that it's
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getting better
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right that's a sign of treatment success
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versus a treatment failure is the next
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time you check it if there's a four-fold
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increase right four times
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increase of what your initial lab was
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right so if it's a one to four
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hopefully it will go down either to one
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to one or it will say non-reactive
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because that's a possibility too
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there's two possibilities so the ch hold
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on a sec for that though but six months
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12 months and 24 months is the
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monitoring parameters after
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the initial treatment of wherever you've
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dropped in
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and then you're checking to see if it's
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a four-fold decrease a four-fold
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increase
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or no change two caveats i want to add
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in here one there's something called
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zero fast
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so some patients especially with those
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low level rpr's reactive
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those patients may not ever
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get like it might not go back down to
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normal it might stay at one to one it
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might stay at one to four right as long
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as it hasn't
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increased over time and they don't have
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symptoms then
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you can continue to check those labs
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versus if they have any symptoms or you
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have concern of there being like
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neurologic things especially like
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neurosyphilis
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those patients need to be referred to
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infectious disease to have a
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conversation about do we need a csf
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sampling do we need a lumbar spine a
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lumbar puncture rather
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to obtain csf for evaluation right and
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i'm not going to make that decision as
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i'm primary care
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but if they have no symptoms we're just
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rechecking the rpr
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titers at 6 months 12 months and 24
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months and hopefully a four fold
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decrease
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one caveat i did want to add about
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symptomatic patients and again i didn't
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talk a ton about symptomatic patients in
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this video because there's a lot more
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to pack in there but for those patients
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there's something called a hook
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effect real fancy and it's not unique to
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syphilis rpr
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testing however it can happen with other
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labs too but basically it's just so high
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that like it almost like over saturates
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the machine or
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they don't get to the point of dilution
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enough to show a result and so it can
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come back
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as a false negative so somebody's
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presenting to you and like oh my gosh
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this is classic textbook syphilis i'm so
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worried about it
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you order an rpr and it's like
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non-reactive it could be that hook
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effective like it's almost like too high
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for them to even measure it you don't
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necessarily have to remember that name
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but the action step you would take in
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that
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case is obviously consulting with
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somebody i do recommend that active
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syphilis consulting
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and then the other one is to call the
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lab and ask them about
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um you know is there a way to address
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that right
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yeah i mean you can remember that it's
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called a hook effect or you can just say
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like i'm worried it's not measured
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because it was too high
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is there a way that you can run that i'm
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sure they'll know what you're talking
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about because they work in the lab or
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hopefully they will every supervisor
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will
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somebody will um but hopefully that's
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helpful that's the most common scenario
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that i see
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um i guess one kind of like other pearl
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to think about and it comes to like the
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neurosyphilis thing so
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one other time um one specific time i'm
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thinking about i had an older woman in
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her 70s had some cognitive impairment
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and one of the lab part of the workup
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for that is syphilis
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i'm doing an rpr hiv some other some
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other labs
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and um her rpr came back reactive and a
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low level reactive i think it was like a
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one to four one to eight
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um and she had cognitive impairment and
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so what i ended up doing was
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um having a consultation with by cult
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calling
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an infectious disease physician that
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actually i had developed a relationship
10:25
with related to our hiv treatment
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program that i was a part of
10:28
um but i also just did some cold calling
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and i have a whole video about that if
10:31
you are nervous about that prospect you
10:33
can totally do it it's amazing
10:35
but anyway having a conversation with
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him of like is this an appropriate
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referral
10:38
do you reckon recommend this person get
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a csf sampling to test for neurosyphilis
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um and what he ended up recommending is
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have her having an appointment
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to discuss and i think that ultimately
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they determined that it wasn't
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um necessary that she and the family
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just
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decided that it wasn't because it
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wouldn't necessarily affect her
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quality of life going forward and
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because she has very likely a late late
11:00
and syphilis that we treated
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and there's not um there's not a yeah it
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was like it was it was a
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risk benefit discussion that they
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ultimately decided not to do that
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but anyway just as a as a general like
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pearl of practice is to get
11:14
other people involved when it comes to
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syphilis but this main approach will be
11:17
helpful for the vast majority of the rpr
11:19
positives that you're seeing and if you
11:21
struggle with labs we'd love to have you
11:23
in the lab interpretation crash course
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education
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and it covers cbc cmp tsh lipids
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in primary care so head on over to real
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labs because it's bomb and it will help
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so much better they're just glowing
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reviews but anyway if you have questions
11:46
about that definitely
11:47
let me or the team know but thank you so
11:49
much for watching let us know what
11:51
questions you have
11:52
hang in there and i'll talk to you soon
11:56
[Music]
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Liz Rohr