TO THE EDITOR
We read with a great interest the study by Ewid et al, that evaluated the connection between inflammatory bowel disease (IBD) and bone mineral density (BMD) in a sample of adult Saudi patients with IBD from a single center.
One important finding of this study was that Crohn’s disease (CD) patients are at a higher risk of developing both osteoporosis and osteopenia than ulcerative colitis (UC) patients, even though the study included more patients with severe clinical disease activity and endoscopic activity in the UC group than in the CD group (25% vs 5%, respectively). In spite of disease severity, 78% of UC patients had normal BMD vs 44% of CD patients. Fracture risk can be increased despite normal BMD. Maldonado et al suggested that current screening does not include all IBD patients at increased risk of fractures. We propose using trabecular bone score (TBS) as a complementary tool; as it discriminates patients at higher risk of fractures better than BMD.
According to demographic characteristics in the study, mesalamine use was significantly higher in the UC compared to CD group (81% vs 10%, respectively). Due to the sample size of UC group an analysis of BMD according to mesalamine use probably could not have been performed nevertheless, the analysis would be highly informative. Hence, we postulate a question: could mesalamine use have contributed to lower risk of developing osteoporosis in UC compared to the CD cohort?
Krajcovicova et al observed no significant difference in the prevalence of low BMD in groups of patients with UC and CD. They observed that corticosteroid therapy and menopause had significant negative effects, whereas combined treatment with an anti-tumor necrosis factor (TNF) α agent and azathioprine had a significant positive effect on Δ BMD at the lumbar spine (BMDL) per year.
The study also showed that low BMI is a risk factor for reduced BMD. According to Fawzy et al and Steinschneider et al, increased BMD commonly reported in overweight women may be a result of soft tissue interference, further supporting addition of TBS as a screening method for osteoporosis in research and clinical practice.
An unexpected finding in this study is the lack of correlation between steroid use and BMD. Paggiosi et al demonstrated that TBS alone and BMDL in combination with TBS, but not BMDL alone were able to discriminate between glucocorticoid-treated and glucocorticoid-naïve women. In the study by Gulyás et al TNF-α inhibition slowed down generalized bone loss in rheumatoid arthritis and ankylosing spondylitis. Effect of anti TNF therapy on bone metabolism was not confirmed by Ewid et al hence, the effect is questionable in IBD.
Addition of TBS would enable inclusion of individuals with normal BMD at increased fracture risk. In conclusion, by including both screening methods osteoporotic fracture risk in UC vs CD cohort could be assessed more accurately.