What's this test for?

This test is ideal if you're experiencing unexplained fluid buildup around your lungs (pleural effusion) and your doctor needs to determine the underlying cause. It helps identify whether the fluid is related to immune system problems, infections, or inflammatory conditions affecting your respiratory system. Many people need this test when they have persistent shortness of breath, chest pain, or unexplained breathing difficulties that suggest pleural fluid issues.

What happens after I get my results?

You'll receive detailed doctor notes in simple language explaining what your complement C4 levels in the pleural fluid mean for your immune system and respiratory health. These notes include personalized recommendations on next steps, such as whether additional immune system testing is needed or if you should follow up with a pulmonologist or rheumatologist. You'll also get the standard lab report and can track your levels over time using our trends feature if monitoring is recommended.

What's included in this test?

This test measures Complement Component C4 specifically in pleural fluid samples. C4 is a protein that plays a crucial role in your immune system's response to infections and inflammation. By measuring C4 levels in the fluid around your lungs, doctors can distinguish between different causes of pleural effusion and identify immune-related disorders or inflammatory conditions affecting your respiratory system.

How should I prepare for this test?

This test requires a pleural fluid sample that must be collected by your healthcare provider through a procedure called thoracentesis. Your doctor will provide specific instructions for the procedure, which typically involves avoiding certain medications that affect blood clotting. The pleural fluid sample will then be sent to the lab for C4 analysis. Follow your healthcare provider's preparation guidelines closely.

Who should consider getting this test?

This test is essential for anyone who has been diagnosed with pleural effusion (fluid around the lungs) and needs to determine the underlying cause. It's particularly important if you have symptoms like persistent shortness of breath, chest pain, chronic cough, or if imaging tests show unexplained fluid buildup. People with suspected autoimmune conditions, lupus, or recurring respiratory issues may also benefit from this test.

What symptoms indicate I may need this test?

You may need this test if you're experiencing persistent shortness of breath, sharp chest pain that worsens with breathing or coughing, dry cough, or unexplained difficulty breathing. Other signs include feeling like you can't take a deep breath, fever without clear cause, or chest heaviness. If imaging tests have already shown fluid around your lungs, this test helps your doctor understand why the fluid is there.

What is complement C4 and why does it matter?

Complement C4 is a protein that's part of your immune system's complement cascade, which helps fight infections and remove damaged cells. When measured in pleural fluid, C4 levels help doctors determine whether fluid buildup is caused by immune system problems, inflammatory conditions like lupus or rheumatoid arthritis, or other issues. Low C4 levels in pleural fluid often suggest immune-related causes, while normal or high levels may point to other conditions.

What does low C4 in pleural fluid mean?

Low C4 levels in pleural fluid often suggest that an autoimmune or immune-related condition is causing the fluid buildup. This is commonly seen in lupus, rheumatoid arthritis, or other connective tissue diseases affecting the lining around your lungs. Low C4 helps doctors distinguish these immune-related causes from other reasons for pleural effusion like infections, heart failure, or cancer.

What causes abnormal C4 levels in pleural fluid?

Abnormal C4 levels in pleural fluid are typically caused by immune system disorders where the complement system is being consumed or activated. Autoimmune conditions like systemic lupus erythematosus (SLE), rheumatoid arthritis, or mixed connective tissue disease commonly lower C4 levels. Certain infections, inflammatory conditions, or immune complex diseases can also affect C4 measurements in pleural fluid.

What happens if my C4 results are abnormal?

If your C4 levels in pleural fluid are abnormal, your doctor will likely order additional tests to identify the specific underlying condition. This may include blood tests for autoimmune markers, additional complement tests, or imaging studies. You'll probably be referred to a specialist like a rheumatologist or pulmonologist who can develop a treatment plan targeting the root cause of your pleural effusion and manage any immune system issues.

Getting your blood test with us is easy, private & backed by the power of science.Long story short: In the test options, use the filters or search box to narrow your choices and find the test you want. If you need a hand navigating through options, text our super friendly support team at 754-799-7833, and we'll provide tailored suggestions to help you find the ideal test. Once your order is placed, we’ll create your doctor’s lab order remotely, without any need for you to make a trip to a doctor in person or to talk to the doctor. Expect to receive your doctor’s lab order right in your inbox. It will also be in your patient portal if you need to find it later. We’ll also include instructions regarding fasting and other requirements for your test. Your patient portal will be auto-created hassle-free during checkout. If this is your first time ordering, you'll be prompted to create a password for instant login access to your patient portal. It's a quick way to conveniently access your orders and results whenever you want. When you’re ready, visit one of our 4,000 locations. Just bring your ID – no printing or faxing of your lab order is needed, as your order and details will already be in the lab system. Note that most lab locations don’t accept walk-ins, so it’s best to book an appointment in advance. Don’t worry – we’ll provide detailed instructions along the way. You’ll get your results via email & SMS and dive into understanding your body better. Yup, that easy! If you have any questions, please text us at 754-799-7833 or email support@privatemdlabs.com and we'll gladly help you.

How do I know which test to get?

In the test options, find the test you want. If you’re not sure which test to get, we can lend a hand in finding the right option. Just text or call us at 754-799-7833, email us at support@privatemdlabs.com, and we'll gladly help you. We've got your back and reply quickly.

When will my lab results be available?

Most test results will be available within 1–3 business days. Once they're ready, we'll send an email and text message to let you know. After your blood draw, just hang tight and don't worry – we'll keep you updated and in the loop! If you have any further questions, please text us at 754-799-7833 or email support@privatemdlabs.com, and we'll gladly help you.

Is it possible to make changes to my lab order if I made a mistake with the name, date of birth, or any other details?

Absolutely! We totally understand that errors can happen. No worries, we're here to help you. Just reach out to us via text at 754-799-7833 or shoot us an email at support@privatemdlabs.com. Remember to include your order number and let us know the correct information you’d like to update. Our awesome team will jump right in and make sure everything is sorted out and accurate for you. There are no changes necessary if your address is wrong on the requisition though. We don’t mail anything out. Our lab requires an address to be listed to generate an order.

Do you accept health insurance?

Only HSA & FSA is accepted. Our services are strictly self-pay and cannot be submitted to your health insurance provider except for Health Savings Accounts or Flexible Savings Accounts. This policy applies to all insurance companies, including federal health insurance programs like Medicare. If you have any questions, please text us at 754-799-7833 or email support@privatemdlabs.com.

Can I cancel my order?

Yes. We get it – sometimes your needs change. As long as your samples haven’t been collected yet, we’re happy to help you cancel your order. If you have any further questions, please text us at 754-799-7833 or email support@privatemdlabs.com. You can read more about our cancellation policy here.

How can I find a lab location near me?

During the ordering process, you’ll be able to select a specific lab near you, with no strings attached! You can switch it up later easily and visit any of our authorized locations as long as it’s the same lab company you selected your test for (Quest Diagnostics or Labcorp). Before you proceed with your order, feel free to browse through all our lab locations here. This will give you the peace of mind of knowing that there's a lab nearby your home, office or your favorite gym. If you have any questions, please text us at 754-799-7833 or email support@privatemdlabs.com and we'll gladly help you.

Pleural Fluid Test - Breathing Issues & Chest Pain

Getting your blood test with us is easy, private & backed by the power of science.

Long story short:

In the test options, use the filters or search box to narrow your choices and find the test you want.
If you need a hand navigating through options, text our super friendly support team at 754-799-7833, and we'll provide tailored suggestions to help you find the ideal test.
Once your order is placed, we’ll create your doctor’s lab order remotely, without any need for you to make a trip to a doctor in person or to talk to the doctor. Expect to receive your doctor’s lab order right in your inbox. It will also be in your patient portal if you need to find it later. We’ll also include instructions regarding fasting and other requirements for your test. Your patient portal will be auto-created hassle-free during checkout.
If this is your first time ordering, you'll be prompted to create a password for instant login access to your patient portal. It's a quick way to conveniently access your orders and results whenever you want.
When you’re ready, visit one of our 4,000 locations. Just bring your ID – no printing or faxing of your lab order is needed, as your order and details will already be in the lab system.
Note that most lab locations don’t accept walk-ins, so it’s best to book an appointment in advance. Don’t worry – we’ll provide detailed instructions along the way.
You’ll get your results via email & SMS and dive into understanding your body better. Yup, that easy!

754-799-7833

[email protected]

Blood Test for Breathing Problems and Chest Pain

Complement Component C4, Pleural Fluid

90 day happiness guarantee

Prescription & fees included

Easy to understand results

Fast & convenient

90 day happiness guarantee

Prescription & fees included

Easy to understand results

Fast & convenient

What's this test for?

How should I prepare for this test?

What's included in this test?

Here’s why 1,000,000+ customers chose us for affordable hassle-free private blood testing.

Blood Test for Breathing Problems and Chest Pain

90 day happiness guarantee

Prescription & fees included

Easy to understand results

Fast & convenient

1,000,000+ blood tests later, here's what our customers say