Syphilis Diagnosis


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Syphilis is an easily diagnosable sexually transmitted infection (STI) and basic tests can be performed at a local genitourinary medicine (GUM) clinic or GP to determine if you are infected or not.  You will be asked for information such as your general medical and sexual history, as well as looking for symptoms common in syphilis infections. Any information that you disclose upon being asked will be treated as confidential or, if conducted at a GUM clinic, not sent to your GP without prior consent. The test required will depend on the stage and severity of the syphilis infection. In some cases, more than one method of testing may be used to add assurance to the correct diagnosis.

Swab testing for syphilis

In individuals who have an early or primary infection, sores may be present on the genital and/or oral regions.  One test involves the swabbing of the affected area to collect a sample for further analysis. The sample is further examined using dark field microscopy to identify if the Treponema pallidus bacteria responsible for causing syphilis infections are present within the wound. If a positive result is found, the bacteria are present at the site that is tested and therefore antibiotic treatment will be required.

Blood testing for syphilis

Another method in which syphilis can be diagnosed or screened for is through taking samples of blood and performing tests on it. Various blood tests have been designed to identify an immune reaction to the bacteria causing the infection. A sample of blood will be taken from a vein within the arm or potentially the hand if taking from the arm proves difficult. This is conducted by a trained medical professional known as a phlebotomist. This blood sample is then sent to a medical pathology laboratory for further analysis. There are two potential tests that can be performed to identify immune reactions within the body to the bacterium. Fluorescent Treponemal Antibody Absorption test (FTA-ABS) and Treponema pallidum Particle Agglutination Assay (TPPA) are used to show antibodies that have been produced to kill the bacteria within the body.

A positive result through these tests indicates that a syphilis infection either is present or may have been present in the past.  It may be the case, especially with FTA-ABS that the test may remain positive for life, even if syphilis can be successfully cured so if you have previously received treatment it is recommended that you keep a record of this to show to the health care provider.  A negative result does not necessarily mean that syphilis is not present. It may be the case that there is yet to be a sufficient level of antibodies present within the body for a positive result indication but the bacteria is still present. This is a reason as to why using various testing methods simultaneously leads to a more thorough diagnosis.  

Following treatment, another test examining antibodies can be used to monitor the levels present. This is referred to as the Rapid Plasma Reagin test (RPR) and allows for any recurrent or persistent infections to be identified so further treatments can be used.  A level of caution should be used when using these tests as a false positive result may occur where conditions such as HIV, lupus, malaria and Lyme disease are present within the individual.  The FTA-ABS test is a far more accurate and reliable method of determining if a syphilis infection is present. As a result it is the primary method used by clinicians.

Lumbar puncture/spinal tap to diagnose syphilis

It is possible that late stage infections have led to complications involving infection of the brain and spinal cord, known as neurosyphilis. If this does occur, another method of testing called a spinal tap may be used to diagnose the condition. A spinal tap involves taking a sample of cerebrospinal fluid (CSF) from the spinal column for analysis to see if the bacteria are present within it. CSF is a clear fluid produced by the ventricles in the brain to serve as a vital protector of the structures of both the brain itself and the spinal cord against any possible damage. A needle is inserted between two bones in the back, called vertebrae, and then a small sample of fluid is withdrawn from the area.  Local anaesthetics are use to ensure that you do not suffer any pain during the process, and in total the procedure tends to last approximately 45 minutes. After the lumbar puncture has taken place, you will be advised to take rest as well as any over the counter pain medication such as ibuprofen, aspirin or paracetamol to relieve any discomfort after the anaesthetics wear off.

The procedure is considered to generally be very safe, although as with anything invasive there are potential side effects that may transpire.  The most common side effect, is a headache that typically begins at least several hours after the procedure and may often be accompanied by dizziness, nausea and vomiting. The headache develops as some of the remaining CSF may leak into surrounding tissues. This problem usually goes away with time, lasting from anywhere between a few hours to over a week. Another potential side effect that is reasonably common in patients is back pain or discomfort. Due to the injection causing slight damage in the surrounding tissues, you may feel tender on the lower back and this may spread down the thighs. Again, this is generally not something you should be concerned over as it is considered to be normal for such a procedure.

Rarer and potentially more dangerous side effects may also be present in patients after the lumbar puncture procedure. Bleeding around the area of needle entry or, more uncommonly, into the epidural space may arise. Furthermore, another potential side effect is suffering a brainstem herniation. This is where pressure is increased within the skull, perhaps due to a brain tumour or other lesion, and after the fluid is drawn the brainstem become compressed, leading to possible complications. This is very uncommon to see in patients and prior to the lumbar puncture a CT or MRI scan should be performed to see if any increased pressure is already pre existing in the skull that may increase the risk of this complication.

The sample is sent to a pathological laboratory for analysis. Microbiologists analysing your sample will be looking to see if it has several key defining features that may indicate infection is present. Firstly, if the fluid has changed colour from its normal clear appearance to having a cloudy, yellow or pinkish tinge to it then infection might be present. Furthermore, tests are performed to assess content of biochemical compounds such as protein and glucose, will elevated levels indicating bacteria may be present. Finally, the bacterium can be searched for specifically using microscopy to identify its present and so by combining multiple findings, a sound diagnosis can be made.

 If you have questions at any time either prior to the procedure or after it has been done, your doctor should be able to answer them and put you at ease with the process.

Post-treatment check up

Following infection and treatment, follow up testing of the blood should occur at regular intervals. It is recommended to go for blood testing 3 months, 6 months, 1 year and 2 years after first seeking treatment to ensure there will be no further complications.

Due to some antibodies still persisting in the blood for years after fighting the infection, further blood tests may come back positive despite you no longer having an active syphilis infection. This may pose a problem if you wish to travel to another country, for example. If you require documentation for travel or emigration purposes, a sexual health clinic or your GP should be able to provide this for you and it will detail the treatment you have received for the previous syphilis infection as well as certification that you are currently clean.  


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