Treponema pallidum hemagglutination assay (TPHA)

What it measures

Detects antibodies specific to Treponema pallidum. It confirms a reactive non-treponemal test or is used as the first step in reverse screening algorithms.

Specimen and preparation

• Specimen: Serum
• Tube: Red top

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Current or past syphilis (usually positive for life)
• Other treponematoses such as yaws
• Treated past syphilis (persists)
• Rare false positives: SLE, Lyme disease, leprosy

Method

Hemagglutination/particle agglutination; treponemal EIA or CLIA

Good to know

Stays positive after treatment, so it cannot monitor therapy; use RPR/VDRL titres for that.

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