The main laboratory indicators for ankylosing spondylitis include the following:

Testing for the B27 gene, formally known as HLA-B27 gene, which is hereditary and commonly found in male patients.

Second, to determine if ankylosing spondylitis is in an active phase, inflammatory markers such as erythrocyte sedimentation rate and C-reactive protein can be checked.

Moreover, the diagnosis of ankylosing spondylitis must involve the sacroiliac joints being affected. Therefore, a CT scan and MRI of the sacroiliac joints can be conducted to determine if there are issues with the sacroiliac joints. If the patient shows symptoms of inflammatory lower back pain, has affected sacroiliac joints, tests positive for the B27 gene, and shows elevated inflammatory markers, then a diagnosis of ankylosing spondylitis can generally be confirmed.