A large rise in the use of biologics in ankylosing spondylitis over the last decade can be explained by an increased awareness of inflammatory back pain and a reluctance to stop therapy in patients who have partially responded to treatment, a PBS review concludes.

According to an outcomes statement from the the PBS drug utilisation sub-committee the number of new AS patients beginning treatment with bDMARDs increased from 453 in 2005 to almost 1,190 in 2014.

In line with this the total number of patients treated with bDMARDs also increased from approximately 1,000 in 2006 to 6,000 in 2014.

A number of reasons were likely to be behind the rise in prescriptions, the committee said in its statement published this week.

For instance the prevalence of AS may have been underestimated when it was first listed as an indication.

A reluctance to stop treatment in patients with a partial response and the treatment of earlier disease may also be factors, the report said.

“Increased familiarity with bDMARDs and improved awareness of inflammatory back pain leading to more referrals from GPs to rheumatologists may be contributing to increasing use over time,” the report said.

Meanwhile, the same report noted that 17% of people had not received methotrexate or sulfasalazine or leflunomide before starting bDMARDs.

Although this was a prescribing requirement the committee said that contraindication to these therapies was “likely to account for the majority of these cases”.