There are a number of ways in which AS is assessed when a diagnosis is made.
A physical examination by a nurse, physiotherapist or the rheumatologist to assess your flexibility and joint tenderness.
Blood tests including erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), which measure the level of inflammation in your body, and a genetic test which can identify if you have the HLA-B27 gene. Around 90-95% of people with AS in Europe carry this particular gene.
X-rays or magnetic resonance imaging (MRI) which will show whether or not there is any inflammation or damage to the joints.
Ongoing assessments may also be carried out to see if there are any changes in your condition.
One or more of the following assessments are normally used.
Bath Ankylosing Spondylitis Disease Activity Index (BASDAI)
BASDAI measures the extent of five main symptoms:
- Fatigue (severe tiredness)
- Spinal pain
- Joint pain/swelling
- Areas of localised tenderness
- Morning joint stiffness
The score, calculated by a healthcare professional, is based on answers to six questions. It will record a score between 1 and 10. A higher score indicates more disease activity. In order to fit the eligibility criteria for anti TNF therapy you would, on average, need to score higher than 4 out of 10.
Bath Ankylosing Spondylitis Functional Index (BASFI)
BASFI measures the impact of AS on your ability to carry out everyday tasks. The score (between 1 and 10), calculated by a healthcare professional, is based on answers to ten questions. A higher score indicates a greater impact on your ability to carry out everyday tasks.
Bath Ankylosing Spondylitis Patient Global score (BAS-G)
BAS-G assesses the effect of AS on your wellbeing over the previous week and the last six months. Based on answers to two questions, a healthcare professional will calculate the score (between 1 and 10). A higher score indicates a greater impact on your wellbeing.
Bath Ankylosing Spondylitis Metrology Index (BASMI)
BASMI measures the impact of AS on the spine's mobility and on your physical ability. A healthcare professional will assess the spine's flexibility and take five clinical measures. The higher the score, the more limited movements are. It is expected that the BASMI score may get higher over time as the disease progresses.
Modified New York Criteria
If you are being assessed to see if you meet the criteria for anti TNF therapy, this is one of the measures that will be used. You need to have:
- Low back pain and stiffness for more than 3 months that improves with exercise but is not relieved by rest
- Limitation of motion of the lumbar spine in the sagittal and frontal planes
- Limitation of chest expansion relative to normal values correlated by age and sex
Additionally, the radiological criteria is:
- Sacroiliitis grade>2 bilaterally or grade 3-4 unilaterally
Visual Analogue Spinal Pain Score
Again, if you are being assessed for anti TNF therapy this is one of the key assessment measures. It is a very simple measure. You will be shown a line of 10cm in length with the words 'No pain' on the left hand end of the line and 'Pain as bad as it could possibly be' at the other end. Usually it is just a line but sometimes there are markings along it from 1 to 10.
You will be asked to put a mark on the line which represents your level of pain at the current time.
If you are being assessed for anti TNF therapy your score would need to be higher than 4 to fit the eligibility criteria.
Last reviewed: April 2012
