The risk factors that predispose a person to AS include:
- Testing positive for the HLA-B27 marker
- A family history of AS
- Frequent gastrointestinal infections
Unlike other forms of arthritis and rheumatic diseases, general onset of AS commonly occurs in younger people, between the ages of 17-45. However, it can affect children and those who are much older. AS is more common in men, but occurs in women as well.
The overall points taken into account when making an AS diagnoses are:
- Onset is usually under 45 years of age.
- Pain persists for more than 3 months (i.e. it is chronic).
- The back pain and stiffness worsen with immobility, especially at night and early morning.
- The back pain and stiffness tend to ease with physical activity and exercise.
- Positive response to NSAIDs (Non- steroidal anti-inflammatory drugs).
- Other symptoms and indicators are also taken into account including a history of iritis or uveitis (inflammation of the eye), a history of gastrointestinal infections (for example, the presence of Crohn’s Disease or ulcerative colitis), a family history of AS, as well as fatigue due to the presence of inflammation.
- The history of your condition (including whether pain and discomfort is waking you during the second half of the night)
- A physical examination
- Blood tests, which may show inflammation
- C-reactive protein (CRP)
- Erythrocyte sedimentation rate (ESR)
- X-rays or a magnetic resonance imaging (MRI) scan.
- X-rays sometimes help to confirm the diagnosis, though they generally don’t show anything unusual in the early stages. As the condition progresses new bone develops between the vertebrae, which will be shown in x-ray images
- MRI scans may show the typical changes in your spine and at the sacroiliac joints at an earlier stage of the disease and before changes can be identified on x-rays.
A blood test can show if there’s inflammation in the body, but only if the condition is in an active phase.