Blood count is one of the common indicators used in the diagnosis, treatment, observation of drug response and prediction of changes in ankylosing spondylitis. Patients with ankylosing spondylitis commonly have normal or high white blood cell counts, anemia, mainly orthochromic anemia, and elevated platelet counts. Decreases in white blood cell or platelet counts may occur with the application of nonsteroidal anti-inflammatory drugs, slow-acting drugs, and immunosuppressive drugs, and increased white blood cell counts during periods of inflammatory activity. If patients who are using biologics are alerted to infection when they develop elevated white blood cells, they should visit the rheumatology department promptly to ensure the safety of the medication. This is because patients applying biological agents can cause tuberculosis, tumor spread, etc., leading to some opportunistic infections.