C4 Complement
Private C4 Complement blood test in London for £89.99, measuring one immune complement marker with results in around 1 business day.
Turnaround time
1 business day
Biomarkers count
1
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Overview of the C4 Complement
The C4 Complement blood test measures Complement Component 4, commonly abbreviated to C4, a protein that forms part of the body's complement immune system.
The complement system consists of a network of proteins that work together to identify pathogens, enhance antibody activity, clear immune complexes and support inflammatory responses.
C4 is particularly associated with the classical and lectin complement pathways. When these pathways are activated, C4 can be consumed, leading to reduced concentrations in the blood.
The test contains 1 biomarker: C4 Complement.
Low C4 concentrations can occur in immune-complex conditions such as systemic lupus erythematosus (SLE), certain forms of vasculitis and cryoglobulinaemia.
C4 is also particularly useful when hereditary or acquired C1 esterase inhibitor deficiency is being investigated because C4 is often reduced in these conditions.
Higher C4 levels are generally less specific and may occur as part of an acute inflammatory response.
C4 is often interpreted alongside C3 because the pattern of the two complement proteins can provide additional information about which part of the complement system may be activated.
An abnormal C4 result does not independently diagnose an autoimmune, inflammatory or complement disorder and should be interpreted alongside symptoms, medical history and other immune investigations.
What Does the C4 Complement Test Check?
This test measures 1 biomarker.
C4 Complement
Measures Complement Component 4, a protein involved primarily in the classical and lectin complement pathways. Reduced C4 can occur with immune-complex consumption, systemic lupus erythematosus and C1 inhibitor deficiency, while increased levels can occur during inflammatory responses.
Who May Benefit From the C4 Complement Test?
This test may be suitable for people undergoing investigation or monitoring of autoimmune, immune-complex or complement-related conditions.
Suspected systemic lupus erythematosus - Reduced C4 can occur when complement proteins are consumed during active immune-complex disease.
Known lupus requiring monitoring - Serial complement measurements may provide useful information about changes in disease activity.
Recurrent unexplained swelling - Low C4 can support further investigation for hereditary or acquired C1 esterase inhibitor deficiency.
Possible hereditary angioedema - C4 is commonly used as an initial complement marker where recurrent angioedema occurs without a typical allergic explanation.
Suspected immune-complex disease - C4 can fall when classical complement activation occurs in disorders involving circulating immune complexes.
Possible vasculitis - Selected forms of vasculitis can be associated with complement consumption.
Cryoglobulinaemia investigation - Low C4 can occur in cryoglobulin-related disease and may provide useful supporting information.
Previously low complement result - Repeat measurement may help determine whether a low C4 concentration persists or changes over time.
Specialist-requested immunology testing - The test can be arranged privately where a rheumatologist, immunologist, nephrologist or GP has specifically requested C4 measurement.
How to Prepare
Do not stop immunosuppressive medication or other prescribed treatment simply to alter a complement result unless specifically instructed by the clinician responsible for your care.
Serial results are often more useful than one isolated measurement, particularly when C4 is being used to monitor established autoimmune disease.
Symptoms and Reasons to Consider the C4 Complement Test
You may wish to consider the C4 Complement test when symptoms or previous laboratory findings suggest autoimmune disease, immune-complex activity or a complement-related condition.
Unexplained joint pain or swelling - Joint symptoms can occur in autoimmune connective-tissue diseases associated with complement consumption.
Persistent or recurrent skin rashes - Certain autoimmune and vasculitic conditions can produce characteristic or unexplained rashes.
Recurrent unexplained swelling - Episodes affecting the face, lips, hands, feet or gastrointestinal tract may prompt investigation for hereditary angioedema.
Abdominal swelling or severe episodic abdominal pain - C1 inhibitor deficiency can produce gastrointestinal angioedema without an external rash.
Previously abnormal autoimmune tests - C4 may provide additional information alongside ANA, dsDNA and other immune markers.
Kidney abnormalities associated with autoimmune disease - Complement measurement may form part of investigation or monitoring of immune-mediated kidney disease.
Unexplained inflammatory symptoms - C4 can contribute to a wider immunology assessment where systemic inflammation remains unexplained.
Known lupus with changing symptoms - Repeat C4 measurement may be useful when disease activity is being reassessed.
These symptoms are not specific to low C4 and can occur in many autoimmune, allergic, infectious and inflammatory conditions.
A low C4 result does not independently diagnose lupus or hereditary angioedema. Where hereditary angioedema is suspected, additional testing including C1 esterase inhibitor concentration and function may be required.
Rapid tongue or throat swelling, breathing difficulty or severe airway symptoms require emergency assessment regardless of previous complement results.
How to Book Your C4 Complement Test
Booking your C4 Complement test with London Blood Tests is simple and designed to fit around your schedule.
Choose the C4 Complement
Select the C4 Complement test online and review the included complement biomarker before booking.
Select your sample collection option
Choose an in-clinic blood draw (+£35) or a home or hotel phlebotomy visit (+£60) where a qualified phlebotomist collects your sample.
Attend your appointment
A trained professional will collect your blood sample safely and efficiently at the clinic or during your arranged home or hotel visit.
Laboratory analysis
Your sample is sent to the laboratory, where C4 Complement is measured using specialist immunology or biochemistry analysis.
Receive your results securely
Your results are sent securely by email, ready to review yourself or discuss with a GP, rheumatologist, immunologist, nephrologist or other suitably qualified healthcare professional.
When Will I Receive My Results?
The expected turnaround time for the C4 Complement test is approximately 1 business day after your sample arrives at the laboratory.
Results are sent securely by email once laboratory analysis and authorisation are complete.
Additional laboratory review or repeat analysis may occasionally extend the expected turnaround.
Understanding Your Results
Your C4 Complement result shows the concentration of Complement Component 4 in your blood according to the reference interval used by the analysing laboratory.
Low C4 can occur when the classical complement pathway is being activated and complement proteins are being consumed.
This pattern is particularly associated with immune-complex diseases such as active SLE, some forms of vasculitis and cryoglobulinaemia.
A markedly reduced C4 with a relatively normal C3 can also occur in hereditary or acquired C1 esterase inhibitor deficiency.
However, low C4 does not independently identify the underlying diagnosis.
Higher C4 concentrations may occur during acute inflammation because C4 can behave as an acute-phase protein.
A normal C4 result does not necessarily exclude autoimmune disease because complement levels may remain within the laboratory range despite ongoing inflammation.
Interpretation is often more useful when C4 is considered alongside C3, clinical symptoms, autoimmune antibodies and previous complement measurements.
Reference ranges vary between laboratories, so your result should be interpreted according to the range stated on your report.
Why Book With London Blood Tests?
Private C4 Complement testing in London - Access targeted C4 measurement through London Blood Tests.
Targeted complement assessment - Measure C4 independently without having to book a broad autoimmune profile.
Relevant to lupus monitoring - C4 is commonly measured during the assessment and follow-up of systemic lupus erythematosus.
Useful in angioedema investigation - Low C4 can support further assessment for C1 esterase inhibitor deficiency.
Relevant to immune-complex disease - C4 can provide additional information when classical complement activation is suspected.
Fast laboratory turnaround - Results are expected approximately 1 business day after the sample reaches the laboratory.
Clinic and home visit options - Choose an in-clinic blood draw or arrange home or hotel phlebotomy depending on location and availability.
Secure results by email - Receive your authorised laboratory result securely once analysis is complete.
Clear pricing before booking - The C4 Complement test is priced at £89.99, with sample collection charges shown separately.
Private C4 Complement Blood Test in London
London Blood Tests provides the C4 Complement blood test in London for people requiring targeted investigation or monitoring of complement activity.
The test costs £89.99 and measures one biomarker: C4 Complement.
C4 forms part of the classical and lectin complement pathways and can be affected by autoimmune disease, immune-complex activity and disorders involving C1 esterase inhibitor.
Clinic appointments are available alongside home and hotel phlebotomy depending on location and availability, providing flexible options for people looking for a private C4 Complement blood test in London.
Results are frequently more informative when interpreted alongside C3 Complement and other immunology investigations.