Understanding Lab Tests for Ankylosing Spondylitis
Written by Private MD Labs Medical Writing Team • Last Updated: September 8, 2025
Ankylosing spondylitis is a chronic inflammatory arthritis that primarily affects the spine and sacroiliac joints. While diagnosis is typically made through a combination of clinical symptoms, physical examination, and imaging studies, specific blood tests play a crucial supporting role by identifying genetic markers and measuring inflammatory activity associated with this condition.
Top Recommended Test
HLA-B27 Antigen
This is the primary genetic marker test for ankylosing spondylitis. The HLA-B27 antigen is present in a majority of individuals with this condition, making it a valuable tool for assessing genetic predisposition and supporting clinical diagnosis when symptoms are present.
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The Role of Blood Testing in Ankylosing Spondylitis
Blood tests cannot definitively diagnose ankylosing spondylitis on their own, but they provide valuable information about genetic predisposition and disease activity. The HLA-B27 antigen test is particularly important, as this genetic marker is found in approximately 90% of people with ankylosing spondylitis, though not everyone with HLA-B27 develops the condition.
Other Relevant Tests
HLA B Low Resolution
This test provides broader HLA-B typing that includes HLA-B27 detection. The presence of HLA-B27 is associated with significantly increased risk of developing ankylosing spondylitis, making this test useful for genetic risk assessment.
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Interleukin 17, Serum
Interleukin 17 is an inflammatory marker that can be elevated in ankylosing spondylitis. Higher levels of this cytokine are associated with increased disease activity and can help monitor inflammation levels in patients with this condition.
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HLA-A, B, C, DRB1 and DQ High Resolution
This comprehensive HLA typing test provides detailed genetic information including HLA-A and HLA-B27 markers. Both HLA-A and HLA-B27 alleles have been strongly associated with increased risk of developing ankylosing spondylitis, offering thorough genetic risk assessment.
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Understanding Your Results
A positive HLA-B27 test indicates genetic predisposition but does not guarantee you will develop ankylosing spondylitis. Many people carry this antigen without ever developing the condition. Conversely, a small percentage of people with ankylosing spondylitis may test negative for HLA-B27. These tests are most valuable when interpreted alongside clinical symptoms and other diagnostic findings.
Important Considerations
The information here is for educational purposes only and is not a substitute for professional medical advice. Always consult with a healthcare provider for diagnosis and treatment.
