- “Nontreponemal test antibody titers might correlate with disease activity and are used to follow treatment response.
- Results should be reported quantitatively. A fourfold change in titer, equivalent to a change of two dilutions (e.g., from 1:16 to 1:4 or from 1:8 to 1:32), is considered necessary to demonstrate a clinically significant difference between two nontreponemal test results obtained using the same serologic test. Sequential serologic tests in individual patients should be performed using the same testing method (VDRL or RPR), preferably by the same laboratory.
- The VDRL and RPR are equally valid assays, but quantitative results from the two tests cannot be compared directly because RPR titers frequently are slightly higher than VDRL titers.
- Nontreponemal test titers usually decline after treatment and might become nonreactive with time; however, in some persons, nontreponemal antibodies can persist for a long period of time, a response referred to as the “serofast reaction.”
- Most patients who have reactive treponemal tests will have reactive tests for the remainder of their lives, regardless of treatment or disease activity. However, 15%–25% of patients treated during the primary stage revert to being serologically nonreactive after 2–3 years.
- Treponemal antibody titers do not predict treatment response and therefore should not be used for this purpose.“
https://www.cdc.gov/std/tg2015/syphilis.htm