How is ankylosing spondylitis (AS) diagnosed?

The diagnosis is typically suspected by the doctor based on the signs and symptoms. The doctor will take a thorough history and do a physical examination. X-rays, especially those of the sacroiliac joints and spine can be confirmatory. The HLA B27 gene may be checked by a blood test, but its presence or absence does not ultimately confirm or reject the diagnosis.

How is reactive arthritis diagnosed?

The diagnosis is typically made by a doctor taking a thorough history and physical examination. A swollen joint may be aspirated to rule out an infection or gout. There is no specific test for the diagnosis of ReA. The HLA B27 gene may be checked by blood test in selected cases, but it is not diagnostic.

Last reviewed by a Cleveland Clinic medical professional on 11/04/2014.


  • Woods RP, Seamon J. Chapter 21. Arthritis & Back Pain. In: Stone C, Humphries RL. eds. CURRENT Diagnosis & Treatment Emergency Medicine, 7e. New York, NY: McGraw-Hill; 2011.
  • Burton JH. Chapter 281. Acute Disorders of the Joints and Bursae. In: Tintinalli JE, Stapczynski J, Ma O, Cline DM, Cydulka RK, Meckler GD, T. eds. Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 7e. New York, NY: McGraw-Hill; 2011.
  • Spondylitis Association of America. Enteropathic arthritis. Accessed 11/4/2014.

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