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Interpretation of bone mineral density values in pediatric Crohn's disease
D Herzog1, N Bishop, F Glorieux
1Department of Pediatrics, Sainte-Justine Hospital, University of Montreal, Quebec, Canada.
Insights
Pediatric Crohn's disease patients often show low bone density. Correcting bone density scores for delayed bone age or height age reveals osteoporosis in 26-30% of cases, not 44%.
Area of Science:
- Pediatric Endocrinology
- Gastroenterology
- Bone Metabolism
Background:
- Crohn's disease (CD) is associated with reduced bone mineral density (BMD) in pediatric patients.
- Growth failure and delayed bone age (BA) and height age (HA) are common in pediatric CD.
- Assessing osteoporosis in these patients using chronological age (CA) may overestimate prevalence.
Purpose of the Study:
- To compare bone mineral density (BMD) z-scores calculated for chronological age (CA) versus those corrected for bone age (BA) or height age (HA) in pediatric CD patients.
- To determine the accurate prevalence of osteoporosis in pediatric CD with growth delay.
Main Methods:
- Prospective study of 43 pediatric CD patients in remission.
- Dual-energy x-ray absorptiometry (DXA) for BMD measurement.
- Assessment of chronological age (CA), bone age (BA), and height age (HA).
Main Results:
- 44% of patients had low BMD z-scores for CA (<-2 SD).
- Among these, 21% had BA more than 2 SD below CA or HA at least 2 years below CA.
- After correction for BA or HA, BMD was abnormal in only 26-30% of cases.
Conclusions:
- Low BMD in pediatric CD patients with growth delay is overestimated when assessed solely by chronological age.
- Bone mineral density assessment requires correction for bone age or height age for accurate osteoporosis diagnosis in these patients.
- This approach refines the understanding of bone health in pediatric Crohn's disease.
Abstract:
Patients with Crohn's disease (CD) often have low bone mineral density (BMD) for their chronological age (CA). However, pediatric cases frequently have growth failure and delayed bone age (BA) and height age (HA). Do they really have the amount of osteoporosis as measured by BMD and calculated for their CA? The aim was to compare z-scores for BMD in relation to CA and z-scores corrected for BA or height age in pediatric patients. A group of 43 pediatric patients (mean age, 12 years; 14 girls, 29 boys) with CD in remission, prospectively had BMD (measured by dual energy x-ray absorptiometry) and BA. Abnormally low z-score for BMD (below 2 standard deviation [SD] for CA was found in 19 patients (44%). Among these, 9 patients (21% overall) had a BA of more than 2 SD lower than their CA and 12 had height age at least 2 years below CA. When the BMD z-score in these patients was corrected for their BA and height age, 6 of 9 and 8 of 12 patients had a normal BMD. In conclusion, when corrected for BA or CA delay, BMD was abnormal in 26 to 30% rather than 44% of cases. Correct assessment of BMD in Crohn's disease patients with bone age delay requires interpretation in terms of BA or HA, rather than CA.