Norwegian researchers have failed to replicate results of a trial showing a large effect of antibiotic treatment for chronic low back pain, casting doubt on a proposed aetiology of low-grade bacterial discitis in certain patients.

The original trial was carried out in Denmark in 2013 in 144 people with low-back pain, a history of disc herniation and type 1 Modic changes (bone oedema) on MRI.

It found patients given 100 days’ treatment with amoxycillin/clavulanic acid (500mg/125mg or 1000mg/125mg, three times daily) had an improvement of 8.3 points compared with placebo on the Roland-Morris Disability Questionnaire at one-year follow-up.

While 6% of the general population have Modic changes in their discs, 40-50% of people with non-specific low back pain have them, the authors of the replication study wrote in the BMJ.