Syphilis Diagnosis and Treatment Guidelines

Diagnostic Considerations

The Centers for Disease Control and Prevention recommends that all patients with suspected syphilis require serologic testing with both nontreponemal tests (RPR or VDRL) and confirmatory treponemal tests (FTA-ABS or MHA-TP) 1, 2
Darkfield examination or direct fluorescent antibody testing of lesion exudate provides definitive diagnosis in early syphilis with visible lesions 2
Nontreponemal tests (RPR/VDRL) are quantitative and used for both diagnosis and monitoring treatment response 1, 2
Treponemal tests confirm the diagnosis but remain positive for life and cannot be used to monitor treatment response 1, 2
A fourfold change in nontreponemal titer (e.g., from 1:16 to 1:4) is clinically significant 2
All patients diagnosed with syphilis must be tested for HIV infection 1, 2
CSF examination is mandatory before treating tertiary syphilis to exclude neurosyphilis, which requires entirely different treatment 3

The American College of Obstetricians and Gynecologists recommends benzathine penicillin G 2.4 million units IM as a single dose for primary and secondary syphilis 1, 2
For penicillin-allergic non-pregnant adults, the Infectious Diseases Society of America recommends doxycycline 100 mg orally twice daily for 14 days 1, 2
Ceftriaxone 1 gram IV/IM daily for 10 days is a reasonable alternative based on randomized trial data showing comparable efficacy 1
The Centers for Disease Control and Prevention recommends that pregnant women must receive penicillin—it is the only therapy proven to prevent maternal transmission and treat fetal infection 4, 1, 3
Pregnant women with penicillin allergy MUST undergo desensitization followed by penicillin treatment—no alternatives are acceptable 4, 1, 3

The Centers for Disease Control and Prevention recommends that HIV-infected patients use the same treatment regimens as HIV-negative patients for all stages of syphilis 1, 3
Closer follow-up is mandatory to detect treatment failure or disease progression in HIV-infected patients 1, 3

The American College of Physicians recommends repeat quantitative nontreponemal tests (RPR or VDRL) at 3, 6, 12, and 24 months after treatment 1, 2
Primary/secondary syphilis: Expect fourfold decline in titer within 6 months 1, 2
Late syphilis: Expect fourfold decline in titer within 12-24 months 1, 3

The Infectious Diseases Society of America recommends never using oral penicillin preparations—they are completely ineffective for syphilis treatment 1, 3
Never switch between different nontreponemal test methods (RPR vs VDRL) when monitoring response—results cannot be directly compared 1, 3
Never skip CSF examination before treating tertiary syphilis—missing neurosyphilis leads to treatment failure 3