7 responses to “Interpretation of Syphilis Serology”

  1. Succinct summary. Useful.

  2. Great simplification if testing. Thanks, also a great reminder as to whom we should consider testing.

  3. Hi – thank you so much for this very helpful summary. Just a note – the treatment for syphilis is IM penicillin G benzathine (2.4 million units) LONG ACTING, divided into 2 doses (1.2 million units each) and injected into the R and L ventrogluteal sites. This formulation can be ordered directly from the BCCDC in pre-filled syringes, divided into the 2 doses. We’ve seen multiple cases of patients treated with a single injection and/or with the short acting formulation, resulting in inadequate treatment.

    For reference: http://www.bccdc.ca/resource-gallery/Documents/Communicable-Disease-Manual/Chapter%205%20-%20STI/CPS_BC_STI_Treatment_Guidelines_20112014.pdf

  4. Excellent summary.
    I was going to comment on the importance of specifying the divided dose of long acting, injected into both ventrogluteal sites (sometimes at the same time, if there is a second clinician available – as this can be more comfortable for the patient). But Chelsea has done a far better job of it.
    I recommend that the authors be asked to edit to include this important detail in their TCMP write up, as not everyone reads these comments.

  5. Thank you for your comments! We made two changes:

    All stages of early syphilis are treated with a single dose of IM penicillin G benzathine (2.4 million units)3.
    CHANGED TO:
    All stages of early syphilis are treated with IM penicillin G benzathine (2.4 million units)3, long-acting formulation, divided into two doses of 1.2 million units each, administered in the right and left ventrogluteal sites.

    Late latent disease, or cardiovascular/gummatous disease without neurosyphilis, are treated with three weekly doses of IM penicillin G benzathine (2.4 million units)3.
    CHANGED TO:
    Late latent disease, or cardiovascular/gummatous disease without neurosyphilis, are treated with three weekly doses of IM penicillin G benzathine (2.4 million units)3, long-acting formulation, each divided into two doses of 1.2 million units each, administered in the right and left ventrogluteal sites.

  6. Thanks for this succinct and clear summary, extremely helpful. I’m wondering if you can comment on what a significant RPR titre rise might be in someone with previous infection that might alert you to re-infection. For instance, If someone’s titre is reduced to 1:2 after treatment and the it increases to 1:4 on a subsequent test, is that indicative of re-infection or would you see a larger increase? Granted I’m sure you need to factor in risk factors and symptoms, but I often see minor variation in RPR over time in those previously infected/treated and am unsure about interpretation.

  7. Hello Nicholas,
    Thanks for your question. An RPR rise of fourfold or greater (i.e. a change of two doubling dilutions, for example from 1:4 to 1:16, or 1:8 to 1:32) is considered clinically significant and would be consistent with reinfection. A minority of individuals will remain “serofast” despite appropriate treatment, meaning they will continue to have detectable low-level RPR antibodies. Most commonly, these are low-level (less than 1:8), and may demonstrate minor variation (a single dilution) over time. In the absence of an exposure, those in a serofast state with only a twofold change in titre would not be considered reinfected and would not require re-treatment. They should continue to be monitored over time.

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