Starting a Biologic for Ankylosing Spondylitis? Here’s What Labs You Need to Know About

If you’ve been diagnosed with ankylosing spondylitis (AS) and your rheumatologist has recommended a biologic medication, you probably have questions. Biologics are highly effective at controlling AS symptoms and slowing disease progression — but like any powerful treatment, they require careful monitoring to make sure you’re being treated safely.

At Chicago Arthritis, our goal is to help patients understand exactly what to expect before and during biologic therapy. Here’s a breakdown of the essential lab work involved.

Why Lab Monitoring Matters for Biologic Therapy

Biologic medications work by targeting specific parts of the immune system to reduce inflammation. Because they affect your immune response, your care team needs to:

• Confirm you’re a safe candidate before starting treatment
• Rule out underlying infections that could become serious once your immune system is suppressed
• Track your body’s response to the medication over time

This is why lab testing happens both before you start and throughout your treatment.

Labs Checked Before Starting a Biologic

Before your first dose, your rheumatologist will order several baseline tests, including:

Complete Blood Count (CBC)

This checks your red blood cells, white blood cells, and platelets to make sure your body is healthy enough to begin therapy.

Chemistry Panel

This evaluates how well your kidneys and liver are functioning, since these organs help process medications.

Inflammation Markers

Tests like sed rate (ESR) and CRP help establish a baseline of your current inflammation levels.

Infectious Disease Screening

This is a critical safety step. Your doctor will screen for:

• Hepatitis B and C
• Tuberculosis (TB)

Why does this matter? If you have an active infection — or even a dormant one — starting a biologic could allow it to reactivate or worsen. In some cases, patients need prophylactic (preventive) treatment before starting their biologic to reduce this risk.

Labs Checked While You’re on a Biologic

Monitoring doesn’t stop once treatment begins. Every few months, your rheumatologist will recheck:

• CBC – to continue monitoring blood cell counts
• Chemistry panel – to keep an eye on kidney and liver function
• Sed rate and CRP – to track how well the medication is controlling inflammation and disease activity

This ongoing testing helps your care team catch any issues early and adjust your treatment plan if needed.

The Bottom Line: Safe, Effective AS Treatment Requires a Team Approach

Biologic medications have transformed the treatment of ankylosing spondylitis, offering many patients significant relief from pain and stiffness. But getting the best — and safest — results requires close collaboration with a rheumatologist who monitors your labs consistently over time.

If you’re managing AS, or any autoimmune or inflammatory condition, don’t go it alone. Working with an experienced rheumatology specialist ensures your treatment stays both effective and safe for the long haul.

Ready to Take the Next Step?

Whether you’re just starting to explore biologic therapy or looking for a second opinion on your arthritis care, the team at Chicago Arthritis is here to help.

👉 Visit ChicagoArthritis.com to learn more or schedule a consultation with a Chicago rheumatologist today.

---

How Ankylosing Spondylitis Differs in Men and Women

Medications for Ankylosing Spondylitis: What You Need to Know (Best Treatments & FAQs Answered!)

The Best Exercises for Ankylosing Spondylitis: Stay Active and Reduce Pain