Measure bone age routinely in Crohn disease

Assessing bone age should be a standard of care for children with Crohn disease, according to new research. Routine measurement would promote more accurate interpretation of growth status and improve treatment.

Impaired growth and delayed puberty accompany Crohn disease in as many as 80% of children with the condition. Accurate evaluation of growth, which is an indicator of disease status, can provide critical guidance for therapy. Failing to take skeletal maturation into account may result in misinterpretation of growth status.

Bone age, assessed by a radiograph of the left hand and wrist, is evaluated in terms of a Z score (BA-Z), which is derived by standardizing bone age results for sex and chronologic age.

To determine the distribution of BA-Z scores in children with Crohn disease, researchers examined radiographs of 49 patients younger than 17 years (mean chronologic age, 13.1 years; mean bone age, 12.2 years). Forty-one percent of the children had low bone age, defined as a BA-Z score less than −2.0. Mean BA-Z score was −1.40±1.50 (standard deviation).

Girls had lower bone age than boys. Other characteristics linked to lower scores included white race, earlier Tanner stage (1 to 3), colonic disease, steroid exposure, and azathioprine/6-MP therapy. No associations were seen between BA-Z score and treatment with infliximab, adalimumab, antibiotics, methotrexate, or 5-aminosalicylate.

The researchers also found that when weight, height, and body mass index measurements were standardized on the basis of bone age, anthropometric Z scores varied significantly from anthropometric Z scores based on chronologic age.

In light of these differences and the finding that delayed bone age occurs often in Crohn disease, the investigators conclude that routine assessment of bone age is necessary to accurately evaluate growth in children with Crohn disease. They note that bone age helps forecast residual growth potential and sheds light on changes in height that occur after therapy, which can in turn improve treatment.

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