What is the Difference Between TPHA and VDRL

The key difference between TPHA and VDRL is that TPHA test is a more sensitive test that can detect Syphilis even in the early stages of the infection while VDRL is a more specific test that is better at detecting late-stage Syphilis.

Syphilis is a sexually transmitted infection (STI) that causes serious health problems. It usually develops in stages such as primary, secondary, latent, and tertiary. Each of these stages has different signs and symptoms. TPHA and VDRL are two tests used for syphilis. All the positive results by a VDRL test should be confirmed by a TPHA test.

CONTENTS

1. Overview and Key Difference
2. What is TPHA 
3. What is VDRL
4. Similarities – TPHA and VDRL
5. TPHA vs. VDRL in Tabular Form
6. FAQ – TPHA and VDRL
7. Summary – TPHA vs. VDRL

What is TPHA?

Treponema Pallidum Hemagglutination (TPHA) test is used to detect antibodies in the blood against syphilis. Syphilis is a sexually transmitted disease. Syphilis is caused by a bacteria called Treponema pallidum. People get this disease if they come in direct contact with a syphilitic lesion known as chancre. TPHA test is done to diagnose Treponema pallidum infection, screen for sexually transmitted diseases, and monitor the treatment of syphilis.

TPHA is a routine blood test that does not require any specification. The results of this test can be interpreted by agglutination intensity, which could range from +1 to +4. Furthermore, the possible side effects of this test include discomfort, soreness, bleeding, light bruising, and difficulty in moving the arm once the sample is collected.

What is VDRL?

VDRL is a nontreponemal serological screening for syphilis. VDRL is also used to assess response to therapy, to detect central nervous system involvement, and as an aid in the diagnosis of congenital syphilis. This test does not look for bacteria; instead, it checks for antibodies the body makes in response to antigens produced by cells damaged by bacteria.

The test results negative for syphilis antibodies suggest that people don’t have syphilis, whereas a positive result for syphilis antibodies indicates the presence of the infection. If a positive result occurs, the doctor will order a more specific test to confirm the results. Furthermore, the risks associated with the test include a mild to severe headache, numbness or tingling in the lower back or legs, lower back or leg pain, bleeding, and infections at the injection.

What are the Similarities Between TPHA and VDRL?

• TPHA and VDRL are two tests that are used to diagnose syphilis.
• Both tests measure antibodies in the serum.
• Both tests have minor associated risks.
• They are not expensive tests.

What is the Difference Between TPHA and VDRL?

TPHA test is a more sensitive test that can detect Syphilis even in the early stages of the infection, while VDRL is a more specific test, which is better at detecting late-stage Syphilis. Thus, this is the key difference between TPHA and VDRL. Furthermore, TPHA measures nontreponemal-specific antibodies in the serum, while VDRL measures treponemal-specific antibodies in the serum.

The infographic below presents the differences between TPHA and VDRL in tabular form for side-by-side comparison.

FAQ: TPHA and VDRL

Which test is more accurate for syphilis?

The most specific test for the diagnosis of syphilis is the direct fluorescent antibody test for pallidum.

Can TPHA be negative after treatment?

TPHA test becomes consistently negative after treatment.

Does negative VDRL rule out syphilis?

VDRL screening test, more specifically, shows positive results in the secondary and latent stages of syphilis, while it can give false-negative results during early- and late-stage syphilis.

Summary – TPHA vs. VDRL

Syphilis is an infection caused by Treponema pallidum. This disease causes sores that are often painless and typically appear on the genitals, rectum, or mouth. Syphilis is a sexually transmitted disease (STD). Sometimes, a baby during pregnancy and childbirth can get this disease through breastfeeding. Syphilis can damage the heart, brain, or other organs. Therefore, it can become life-threatening. TPHA and VDRL are two tests that are used for syphilis. TPHA seems to be a more sensitive test to diagnose syphilis at the early stage, while VDRL is a specific test that is used to diagnose syphilis at the late stage. All the positive results of a VDRL test should be confirmed by a TPHA test. So, this summarizes the difference between TPHA and VDRL.

Reference:

1. Nayak, Surajit, and Basanti Acharjya. “VDRL Test and Its Interpretation.” Indian Journal of Dermatology, U.S. National Library of Medicine.
2. “Treponema Pallidum Particle Agglutination Assay.” Wikipedia, Wikimedia Foundation.

Image Courtesy:

1. “Treponema pallidum-Partikelagglutinationstest” By Copacopac – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “VDRL slide 2” By Netha Hussain – Own work (CC BY-SA 3.0) via Commons Wikimedia