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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: T pallidum by TP-PA

Test Code(s): TPPA / XMHATP

CPT Code(s): 86780

Methodology: Gelatin Particle Agglutination

Clinical Significance: Confirmatory test for reactive non-treponemal screening tests (RPR or VDRL) for syphilis.

Testing Site: Testing will be sent to an approved reference laboratory.

Days Performed: Mon-Fri.

Turnaround Time: Routine: 2 - 3 days.


Specimen Requirements

Specimen: Blood

Collection Container: Preferred: Red top

Collection Volume: Preferred: 4 mL
Pediatrics: 3 mL

Sample Analyzed: Serum

Volume Required: Preferred: 2 mL
Pediatrics: 1 mL

Specimen Processing: Centrifuge. Transfer cell free serum to plastic vial. Refrigerate.

Specimen Transport: Transport specimen to UWHC Core Laboratory (B4/220). Transport with coolant pack if coming from outreach location.  


Interpretation

Interpretive Guidelines:

A reactive TP-PA test result confirms the reactivity of the nontreponemal test (VDRL or RPR) used as the initial test for syphilis. A reactive TP-PA result suggests current or past infection with pathogenic treponemes. A reactive TP-PA test may also support the diagnosis of late syphilis or long-standing late-latent syphilis in the small proportion of such cases in which the nontreponemal test has become non-reactive, but infection is suspected because of the clinical presentation or a history consistent with syphilis infection.

Syphilis

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