Antistreptolysin Titre (ASOT)
Private ASOT testing in London for £88, measuring one streptococcal antibody marker with results expected in around 1–2 days.
Turnaround time
1-2 business days
Biomarkers count
1
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Overview of the Antistreptolysin Titre (ASOT) Test
The Antistreptolysin Titre (ASOT) blood test measures antibodies produced against streptolysin O, a toxin produced by certain strains of Group A Streptococcus.
The test assesses 1 streptococcal antibody marker: Antistreptolysin Titre/ASOT.
Group A Streptococcus can cause several infections, including streptococcal sore throat and scarlet fever.
The immune system produces Antistreptolysin O antibodies after exposure to streptolysin O.
These antibodies do not usually become detectable immediately.
ASO levels generally begin to rise after the acute infection and may remain elevated for weeks or months.
This makes ASOT particularly useful when investigating recent previous streptococcal infection, rather than diagnosing a sore throat that is happening at the moment.
The test can be important where post-streptococcal complications are being considered.
These include acute rheumatic fever and post-streptococcal glomerulonephritis.
In these conditions, the original throat or skin infection may already have resolved by the time inflammatory complications develop.
Demonstrating a recent immune response to Streptococcus can therefore provide useful supporting evidence.
A single raised ASOT does not necessarily prove that current symptoms are caused by a post-streptococcal complication.
Background antibody concentrations vary between people and populations.
A rising titre on paired samples can sometimes be more informative than one isolated measurement.
ASOT can also be less sensitive after some streptococcal skin infections.
Other antibodies, such as Anti-DNase B, may occasionally provide additional evidence of recent streptococcal exposure.
What Does the Antistreptolysin Titre (ASOT) Test Check?
The test measures antibodies directed against streptolysin O and can provide evidence of a recent immune response to Group A Streptococcus. This test measures 1 specialist biomarker.
Antistreptolysin Titre/ASOT
Measures antibodies produced against streptolysin O, supporting investigation of recent streptococcal exposure and selected post-streptococcal inflammatory complications.
Who May Benefit From the Antistreptolysin Titre (ASOT) Test?
ASOT is most useful where a previous Group A Streptococcus infection is suspected to be relevant to a later inflammatory illness.
People undergoing investigation for acute rheumatic fever - Evidence of a recent streptococcal infection can support the wider diagnostic assessment.
People undergoing investigation for post-streptococcal glomerulonephritis - ASOT may provide evidence of recent streptococcal exposure alongside kidney and urine findings.
People with inflammatory symptoms following a recent sore throat - Antibody testing can be useful after the original infection has resolved.
People with a previous streptococcal infection and new joint symptoms - Post-infectious inflammatory complications may require further assessment.
People with an unexplained raised ASOT on previous testing - Repeat measurement can help assess whether titres are changing.
People whose throat culture is now negative but recent infection remains clinically relevant - ASOT reflects the immune response rather than detecting current bacteria.
People advised to demonstrate previous streptococcal exposure - The test can contribute to a broader infectious or rheumatological investigation.
People under specialist assessment for post-streptococcal disease - ASOT may be interpreted alongside inflammatory markers and organ-specific investigations.
How to Prepare
Antibiotic treatment should not be stopped or delayed simply to obtain an ASOT result.
The test reflects the immune response to previous streptococcal exposure rather than directly detecting bacteria.
Symptoms and Reasons to Consider the Antistreptolysin Titre (ASOT) Test
ASOT testing is generally considered when symptoms develop after a possible streptococcal infection rather than during an uncomplicated acute sore throat.
Joint pain or swelling following a sore throat - Migratory inflammatory joint symptoms can occur in acute rheumatic fever.
Fever with post-streptococcal inflammatory symptoms - Recent infection history can be relevant to the investigation.
New heart symptoms following suspected streptococcal infection - Rheumatic fever can affect the heart and requires urgent clinical assessment.
Blood or protein in the urine after infection - Post-streptococcal glomerulonephritis can affect kidney filtration.
Swelling around the eyes or legs after infection - Fluid retention can occur with significant kidney involvement.
A recent episode of scarlet fever or confirmed streptococcal throat infection - ASOT can provide evidence of the subsequent antibody response.
A previous raised ASOT result - Repeat titres can sometimes clarify whether the antibody concentration is changing.
Suspected post-infectious inflammatory disease - ASOT can contribute supporting evidence where Streptococcus is considered relevant.
ASOT does not diagnose an active streptococcal throat infection.
A throat swab or other direct microbiological test is more appropriate when current strep throat is suspected.
Chest pain, severe shortness of breath, significant swelling, reduced urine output or symptoms suggesting serious cardiac or kidney involvement require prompt medical assessment.
How to Book Your Antistreptolysin Titre (ASOT) Test
The Antistreptolysin Titre test can be booked privately for assessment of the antibody response to recent streptococcal exposure.
Choose the Antistreptolysin Titre (ASOT)
Select the individual ASOT blood test online.
Select your sample collection option
Choose an in-clinic blood draw or professional home or hotel phlebotomy where suitable.
Attend your appointment
A trained healthcare professional collects the required venous blood sample and recent infection history can be documented.
Laboratory analysis
Your serum undergoes laboratory measurement of Antistreptolysin Titre/ASOT.
Receive your results securely
Your authorised result is delivered securely and can be interpreted alongside symptoms, inflammatory markers and other post-streptococcal investigations.
When Will I Receive My Results?
The current live London Blood Tests page lists a turnaround of approximately 1–2 days after laboratory receipt for Antistreptolysin Titre (ASOT).
The sample undergoes laboratory antibody analysis, quality-control procedures and result authorisation.
Turnaround begins when the specimen reaches the laboratory rather than necessarily from the exact time of blood collection.
Where paired titres or additional tests are needed, the complete clinical investigation can take longer.
Understanding Your Results
A raised ASOT indicates that antibodies against streptolysin O are present above the laboratory's expected threshold.
This can provide evidence of recent previous exposure to Group A Streptococcus.
It does not show that active bacteria are currently present.
The timing of the test is important because ASO antibodies usually rise after infection rather than immediately.
A single elevated titre can reflect an infection that occurred weeks or even months earlier.
For this reason, the result must be interpreted alongside symptoms and the timing of the suspected infection.
Where needed, repeat testing can demonstrate whether the titre is rising or falling.
A low or negative ASOT does not completely exclude previous streptococcal infection.
Responses can vary, and ASO may be less sensitive after certain skin infections.
Additional streptococcal antibody testing can sometimes be appropriate where clinical suspicion remains high.
Why Book With London Blood Tests?
London Blood Tests provides private ASOT testing for investigation of recent streptococcal exposure and selected post-streptococcal complications.
Measures the immune response to streptolysin O - The test assesses the exact Antistreptolysin Titre/ASOT biomarker.
Useful after a previous streptococcal infection - Antibodies can remain detectable after the original infection has resolved.
Relevant to rheumatic fever investigation - Evidence of preceding Streptococcus exposure can provide important supporting information.
Relevant to post-streptococcal kidney investigation - ASOT can contribute alongside urine and kidney-function testing.
Can be repeated to assess titre changes - Paired measurements can occasionally provide more information than one isolated result.
Rapid laboratory turnaround - Results are currently expected approximately 1–2 days after laboratory receipt.
Professional blood collection - Clinic and suitable home or hotel phlebotomy appointments are available.
Clear pricing - The Antistreptolysin Titre (ASOT) test costs £88.
Private Antistreptolysin Titre (ASOT) Blood Test in London
London Blood Tests provides private Antistreptolysin Titre testing for people requiring laboratory evidence of a recent immune response to Group A Streptococcus.
The test costs £88 and assesses 1 specialist biomarker: Antistreptolysin Titre/ASOT.
Results are expected approximately 1–2 days after laboratory receipt.
ASOT is most useful during investigation of post-streptococcal complications and is not a direct test for active streptococcal throat infection.