Clinical effect modifiers of antibiotic treatment in patients with chronic low back pain and Modic changes - secondary analyses of a randomised, placebo-controlled trial (the AIM study)

• Published in: BMC musculoskeletal disorders 2020-07, Vol.21 (1), p.458-458, Article 458
• Main Authors: Bråten, Lars Christian Haugli, Grøvle, Lars, Espeland, Ansgar, Pripp, Are Hugo, Grotle, Margreth, Helllum, Christian, Haugen, Anne Julsrud, Froholdt, Anne, Rolfsen, Mads Peder, Nygaard, Øystein Petter, Lutro, Olav, Kristoffersen, Per Martin, Anke, Audny, Schistad, Elina Iordanova, Skouen, Jan Sture, Brox, Jens Ivar, Zwart, John-Anker, Storheim, Kjersti
• Format: Article
• Language: English
• Subjects: Administration, Oral; Amoxicillin; Anti-Bacterial Agents - therapeutic use; Antibiotic; Antibiotics; Back pain; Basale medisinske, odontologiske og veterinærmedisinske fag: 710; Basic medical, dental and veterinary science disciplines: 710; Care and treatment; Chronic low back pain; Clinical trials; Data collection; Effect modifier; Humans; Hypotheses; Intention; Intervertebral discs; Low back pain; Low Back Pain - diagnostic imaging; Low Back Pain - drug therapy; Lumbar Vertebrae - diagnostic imaging; Magnetic resonance imaging; Male; Medical disciplines: 700; Medisinske Fag: 700; Modic changes; Musculoskeletal diseases; Patients; Population studies; Randomised; Sleep; Statistical analysis; Studies; Subgroup; Surgery; Treatment Outcome; Variables; VDP; Vertebrae
• ISSN: 1471-2474; 1471-2474
• DOI: 10.1186/s12891-020-03422-y

Randomised trials on antibiotic treatment for patients with chronic low back pain and vertebral endplate changes visible on MRI (Modic changes) have shown mixed results. A possible explanation might be a real treatment effect in subgroups of the study populations. The purpose of the present study was to explore potential clinical effect modifiers of 3-months oral amoxicillin treatment in patients with chronic low back pain and type I or II Modic changes at the level of a previous lumbar disc herniation. We performed analyses of effect modifiers on data from AIM, a double-blind parallel-group multicentre trial. One hundred eighty patients with chronic low back pain, previous disc herniation, Modic change type I (n = 118) or type II (n = 62) were randomised to 3-months oral treatment with 750 mg amoxicillin (n = 89) or placebo (n = 91) three times daily. The primary outcome was the Roland-Morris Disability Questionnaire (RMDQ) score (possible values 0-24) at 1-year follow-up in the intention-to-treat population. The predefined minimal clinically important between-group mean difference was 4 RMDQ points (not reached in the primary analysis of AIM). Predefined baseline characteristics were analysed as potential effect modifiers, four primary (type I Modic changes, previous disc surgery, positive pain provocation test, high CRP) and five exploratory (disturbed sleep, constant low back pain, short duration of low back pain, younger age, and male) using ANCOVA with interaction terms. None of the four primary potential effect modifiers had strong evidence of modifying the treatment effect. In patients younger than 40 years the difference in mean RMDQ score between the treatment groups was - 4.0 (95%CI, - 6.9 to - 1.2), compared to - 0.5 (95%CI, - 2.3 to 1.3) in patients 40 years or older, both in favour of amoxicillin treatment (exploratory analysis). We did not find evidence for convincing clinical effect modifiers of antibiotic treatment in patients with chronic low back pain and Modic changes. Our results for younger age in these explorative analyses should not affect clinical treatment decisions without confirmation in future studies. ClinicalTrials.gov NCT02323412 , First registered 23 December 2014.