TP-PA: Treponema pallidium Particle Agglutination, Syphilis Serology: TP-PA Serum

Tube Type

Test ID   LAB5172
EPIC Order
   TP-PA
CPT Code(s)   86780
Group/Individual Test   Individual
Laboratory   Clinical Immunology
Tube Station   30
Specimen Routine: 0.5 mL blood/Gold SST tube; See Comments 
Availability Routine: Once per week
  STAT: N/A
Turnaround Time   1-7 days
Reference Range   Non-reactive
Comments
  • The Treponema pallidum particle agglutination (TP-PA) test is used as a confirmatory test for samples demonstrating reactive Rapid Plasma Reagin (RPR) test results. 
  • Once positive, treponemal antibodies typically remain positive for years in contrast to non-treponemal antibody titers that may decline during late syphilis or with effective therapy.  
  • The TP-PA test is performed as a reflex test on reactive RPR samples.  It may be performed on non-reactive RPR samples upon request if late syphilis is suspected. 
  • Results are reported as reactive or non-reactive.  Rarely, an indeterminate result may be obtained.

Reviewed by J. Carr on November 04, 2025

UNC Hospitals
McLendon Clinical Laboratories
101 Manning Drive
Chapel Hill, NC 27514