Role of HLA-B27 Testing in Ankylosing Spondylitis

Diagnostic Value of HLA-B27

HLA-B27 testing should be used as a screening parameter rather than a definitive diagnostic test, with approximately 30-40% of patients with chronic back pain and positive HLA-B27 ultimately receiving an AS diagnosis, according to the Annals of the Rheumatic Diseases 1
HLA-B27 positivity increases the likelihood of peripheral spondyloarthritis, but a negative result should not rule out spondyloarthritis, as stated by the American Academy of Family Physicians 3

Refer to a rheumatologist if the patient has chronic back pain (>3 months) with onset before age 45 AND at least four of the following criteria, including back pain occurring before age 35, waking at night due to pain, buttock pain, improvement with exercise or within two days of NSAID use, first-degree relative with spondyloarthritis, or current or previous arthritis, enthesitis, or psoriasis, as recommended by the American Academy of Family Physicians 3

Inflammatory back pain characteristics are essential for diagnosis, especially in HLA-B27 negative patients, according to the American College of Rheumatology 2
Radiography should be discussed with patients who may have axial spondyloarthritis (with mature skeleton), and if sacroiliitis on radiography meets modified New York criteria, diagnosis can be confirmed, as stated by the American Academy of Family Physicians 3

Do not rule out spondyloarthritis based solely on a negative HLA-B27 test, normal C-reactive protein, or normal erythrocyte sedimentation rate, as advised by the American Academy of Family Physicians 4
Avoid using HLA-B27 early in the diagnostic approach before increasing pre-test probability with clinical parameters, according to the Annals of the Rheumatic Diseases 1

HLA-B27 testing costs approximately €40 (in Germany, equivalent to a chest or pelvis X-ray), and testing only needs to be performed once in a patient's lifetime, as reported by the Annals of the Rheumatic Diseases 1