Sexual Health | Pathology | Diagnosing Syphilis

Diagnosing Syphilis
Session Overview
Description
This session explains how to diagnose syphilis. It describes what samples to take and their storage and transport. It explains diagnostic tests, how to perform them, their sensitivity and specificity and their potential advantages or disadvantages. The timescales between exposure and tests becoming positive are discussed, as is the interpretation of test results after treatment.

Learning Objectives
By the end of this session you will be able to:

• Identify which samples should be taken to make a diagnosis of syphilis
• Describe how these samples should be stored and transported
• Identify the tests that are available and appropriate to detect syphilis
• Interpret the results of tests for syphilis
• State the timescale between exposure to infection and tests for syphilis becoming positive
• Interpret tests for syphilis following treatment

Prerequisites
Before commencing this session you should complete sessions:

• HIV-STI 02 - Pathology/Interpreting Laboratory Tests (260_0018)
• HIV-STI 02 - Pathology/Antigen and Antibody Tests (260_0019)
• HIV-STI 02 - Pathology/Nucleic Acid Amplification Tests (260_0020)

Syphilis occurs worldwide and is due to infection with the bacterium Treponema pallidum subspecies pallidum (Fig 1). Related pathogenic treponemes cause the endemic treponematoses.

T. pallidum is a spirochete, a motile spiral-shaped organism, 5 to 15 µ m long, with 6-14 coils and pointed ends. It was identified as the cause of syphilis in 1905 (Schaudinn and Hoffman).

Syphilis is usually transmitted sexually, by direct contact with an infectious lesion. Vertical transmission from mother to child also occurs, usually in utero. Other routes of infection, e.g. via infected blood products, are uncommon. Approximately 30-60% of sexual contacts of individuals with early syphilis will acquire the infection.