What stage of syphilis is indicated by a reactive Rapid Plasma Reagin (RPR) test at 1:32 dilutions and a reactive Treponema Pallidum Particle Agglutination (TPPA) test?

Staging Syphilis with RPR 1:32, Reactive Antibody, and Reactive TPPA

This serologic pattern (reactive RPR at 1:32, reactive treponemal antibody, reactive TPPA) indicates active syphilis infection, but the specific stage cannot be determined from serology alone—clinical examination and history are essential to distinguish between primary, secondary, early latent, or late latent syphilis. 1

Understanding the Serologic Results

Your test results show:

• Reactive RPR at 1:32 titer: This indicates active disease, as titers ≥1:8 are highly specific for true syphilis infection with false-positives being extremely rare at this threshold 1
• Reactive treponemal tests (TPPA and antibody): Confirms T. pallidum infection 1, 2
• The combination: Both nontreponemal (RPR) and treponemal tests are positive, which is the expected pattern for active syphilis 2

Why Serology Alone Cannot Determine Stage

The RPR titer of 1:32 can be seen across multiple stages of syphilis 1:

• Primary syphilis: Characterized by chancre/ulcer at infection site, with RPR sensitivity 88.5% 1
• Secondary syphilis: Manifests with rash, mucocutaneous lesions, and adenopathy, with RPR sensitivity approaching 100% 1, 3
• Early latent syphilis: Infection acquired within past 12 months without clinical signs, with RPR sensitivity 85-100% 1
• Late latent syphilis: Infection >12 months or unknown duration without clinical signs, with RPR sensitivity 61-75% 1

Critical Clinical Assessment Required

To determine the stage, you must evaluate for:

Signs of Primary Syphilis

• Presence of chancre or ulcer at infection site (genitals, anus, mouth) 1

Signs of Secondary Syphilis

• Skin rash (often involving palms and soles) 1, 3
• Mucocutaneous lesions 1
• Generalized lymphadenopathy 1
• Condyloma lata 1

Signs of Tertiary/Neurosyphilis (Red Flags)

• Neurologic symptoms (headache, vision changes, hearing loss, confusion) 2, 4
• Ocular symptoms (uveitis) 1
• Cardiovascular manifestations 4
• Gummatous lesions 2

Timing Assessment for Latent Syphilis

• Document when patient was last known to be seronegative 1
• Assess sexual history to determine if infection likely occurred within past 12 months (early latent) versus >12 months or unknown duration (late latent) 1

Treatment Implications Based on Stage

The stage determination is critical because treatment differs:

• Primary or secondary syphilis: Benzathine penicillin G 2.4 million units IM single dose 1
• Early latent syphilis: Benzathine penicillin G 2.4 million units IM single dose 1
• Late latent or unknown duration: Benzathine penicillin G 2.4 million units IM once weekly for 3 weeks 1, 2
• Neurosyphilis: Aqueous crystalline penicillin G 18-24 million units per day IV for 10-14 days 1

Additional Mandatory Assessments

• HIV testing: All patients with syphilis should be tested for HIV, as HIV-infected patients may have atypical presentations and require more frequent monitoring 1, 2, 4
• CSF examination: Consider lumbar puncture if neurologic/ocular symptoms present, or for HIV-infected patients with late latent syphilis 1, 4
• Partner notification: All sexual contacts should be evaluated and treated 1

Common Pitfall to Avoid

Do not assume that a specific RPR titer correlates with a specific stage—while higher titers are more common in secondary syphilis, there is significant overlap across stages, and clinical correlation is mandatory for accurate staging 1, 5