TPHA Blood

TPHA Blood Test:

TPHA Blood

TPHA Blood. The Treponema pallidum hemagglutination (TPHA) test was carried out on 274 sera known to show biological false positive reactions to regain tests for syphilis. The Treponema pallidum immunization (TPI) and fluorescent treponemal antibody absorption (FTA-ABS) tests were non-reactive on all these sera. Thirty-one or 11.3% showed reactive results in the TPHA test. Sera from 267 people who had lepromatous leprosy were also tested in the TPHA test. Fourteen sera were reactive in the TPHA, TPI, and FTA-ABS tests and were from people who had both syphilis and leprosy. Biological false positive reactions were shown by 26 of the leprosy sera, of which three or 11.5% were also reactive in the TPHA test. A further four sera in the leprosy group were reactive only in the TPHA test. The possible cause of false reactive TPHA test results is discussed. It was concluded that where regain and TPHA tests are reactive in a person who has no history or clinical signs of syphilis, the serum should be referred for TPI and FTA-ABS testing.

What Are The Symptoms Of Syphilis Infection?

The TPHA symptoms depend upon what stage of syphilis the patient is. The first is the primary stage that occurs only after a period of 3 to 4 weeks the person has contracted the bacteria. The initial symptoms begin with a small round sore that is seemingly painless. It can be transmitted if anyone comes in direct contact with the sore. During the secondary stage, the person may develop skin rashes and sore throat. Other than these some may also have fatigue, weight loss, aching joints and headache. The third stage of the disease is called the latent stage or the hidden stage. One may not find any noticeable symptoms at this stage, but the bacteria remain active inside the body. The last stage of the infection is called tertiary syphilis and is considered to be one of the most life-threatening stages. Some of the potential outcomes include memory loss, mental illness, blindness etc.

How Is The Tpha Test Done?

The TPHA blood test is a simple blood routine and does not require any specific preparations. A sample for the test is drawn by injecting the needle into a vein in your arm. Later it is sent to the lab for further analysis. In the lab, the TPHA test procedure is carried out by using a test card with three wells.

In the first one 10μL of the patients, the serum sample is added. Next 190 μL of the diluent is added and mixed using a micropipette.

In the second well 75μL of the control cells.

In the third 75μL of the test cells are added. After this 25μL of diluted serum is added on each of the wells and the contents are mixed thoroughly. The plate is then incubated for 45-60 mins in room temperature away from direct sunlight. Running a positive and negative control along with the test serum is mandatory.

How To Interpret The Tpha Test Results?

The TPHA test meaning can be interpreted by the agglutination intensity that could range from – to 4+. Understanding these cases gives a clear picture of the TPHA positive results.

The TPHA lab test positive results could be interpreted as follows

1. It is 4+ if there is a uniform mat of the cells covering the entire well.

2. It is 3+ if most of the well is covered by a uniform mat of cells.

3. A lesser density mat surrounded by a slight ring(+2) is another scenario of a TPHA test positive

4. The intensity of the mat decreases and is surrounded by a denser ring with a distinctly open centre.

If there is a small clear center and the cells are settled to a compact bottom, the result can be interpreted as TPHA negative. In case of a TPHA test negative or the results confer to the TPHA test normal range there is no further investigation required. But in case, of an intermediate positive result, MHATP and FTA-ABS test are prescribed.

Results and Interpretation:

ResultsTest CellsControl Cells
Strongly ReactiveFull cell pattern covering the bottom of the well.No agglutination tight button
Weakly ReactiveCell pattern covers approx. 1/3 of well bottomNo agglutination tight button
Indeterminate (Equivocal)Cell pattern shows a distinctly open centerNo agglutination tight button
NonreactiveCells settled to a compact bottom, typically with a small clear center.No agglutination tight button

If the controls (positive control and negative control) do not give the expected result, all assays performed in that batch are invalid and must be tested again.

Reactive (R): Reactive results may indicate an active, past, or successfully treated infection. A diagnosis should be made with a careful history of the patient and a physical examination as well as pertinent laboratory results.

  1. Indeterminate: indeterminate results are confirmed with the MHATP and FTA-ABS test.
  2. False Positive results: Although TPHA test is highly specific, false-positive results have been known to occur in patients suffering from leprosy, infectious mononucleosis, and connective tissue disorders. For confirmation, FTA-ABS test should be used

Quality Control

Positive and negative control are included in the test kit  for the quality control. Control should be recommended in the following cases:

  • At least once a run
  • At least once within 24 hours
  • When changing vial of reagent.

If the control is not showing expected results; the test is invalid (whatever be the test results).


If your test results come out to be positive TPHA disease it is imperative to undergo the complete treatment. The TPHA positive treatment requires you to complete the full antibiotics course even if the symptoms subside. Failing to do so can trigger a relapse.

By Mehfooz Ali

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2 thoughts on “The Treponema pallidum hemagglutination:”
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