Ask your doctor

Back to basics on AS by a rheumatologist

With rheumatology appointments, it’s often the same story: time tends to be short and your list of questions long. So let rheumatologist Dr Ronan Kavanagh help out with answers to common questions asked by people who are newly diagnosed with ankylosing spondylitis.

How can you be sure it’s AS?

AS is usually suspected in younger patients with chronic back pain lasting more than a few months. Because only about 1 in 20 patients with chronic low back pain have AS,1 doctors tend to have to look for additional clues to then suspect a diagnosis. The back pain associated with AS is known as ‘inflammatory back pain’. Inflammatory back pain is usually associated with stiffness which is worse in the mornings, after resting or at night. The symptoms often improve with exercise and anti-inflammatory medications.

Physical examination can be useful, but making a firm diagnosis will usually involve some additional blood tests, X-rays, scans and usually a referral to a rheumatologist.

Do I need an MRI scan to get a diagnosis?

MRI is one of the most useful tools for making a firm AS diagnosis, especially a scan of the sacro-iliac joints. This is different from a standard MRI scan of the lower back (lumbar spine), which is used to diagnose the cause of lower back pain. The standard MRI scan may not be sufficient to diagnose AS.

What is the HLA B27 test?

This is a blood test for the HLA B27 gene, which can be associated with AS.2 Because many people with AS have got the gene, it can be very helpful in making a diagnosis. There are also perfectly healthy people (8%) that carry the gene who will never develop AS:3 having the gene does not necessarily mean that they have the disease. The test is most useful in confirming a diagnosis where there is already a strong suspicion that AS is present.

Will I be able to have children with AS?

Yes. AS, and most of the treatments used, do not reduce fertility. Some, but not all doctors may suggest that women with AS discontinue certain medications in the lead-up to conception and pregnancy. The good news is that it is not unusual for women with AS to find their AS symptoms improve during pregnancy.

Certain precautions may need to be taken at the time of delivery (especially where an epidural is planned) and with medications if breast feeding is planned.

Does having AS mean my children will get it too?

Not necessarily. Although genetics play a role in the development of AS, many other factors are relevant. If a parent with AS happens to be ‘HLA B27 positive’ (i.e. they carry the HLA B27 gene) there is a 50% chance the gene will be passed onto their offspring. But that isn’t always sufficient to pass on the disease. Most of those who inherit the gene, however, will not develop AS – the risk runs from about 6.9% up to 27%.4 For those not carrying the HLA B27 gene the risk is very low.