BMD, back pain history can identify children at high risk for prevalent vertebral fractures
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Bone mineral density at the lumbar spine and back pain history can be used in targeted case findings to identify children with the highest risk for prevalent vertebral fracture so that radiography can be used judiciously, according to findings published in the Journal of Bone and Mineral Research.
“Vertebral fractures are readily diagnosed in the lumbar spine and in most of the thoracic spine using standard spine radiographs,” Leanne M. Ward, MD, FRCPC, research chair in pediatric bone health and professor of pediatrics at the University of Ottawa in Ontario, Canada, and scientific director of the Ottawa Pediatric Bone Health Research Group, and colleagues wrote in the study background. “Due to concerns about cumulative radiation exposure in the pediatric population, however, it is not standard practice to perform spine radiographs in many of these conditions. Instead, radiographs are often only done when a patient develops new back pain or is found to have a very low BMD. Vertebral fractures are frequently asymptomatic, however, so relying on the presence of back pain will miss many fractures.”
Ward and colleagues analyzed data from 400 children participating in the STOPP research initiative, a natural history study examining the development of vertebral fracture and other markers of bone health in children with diseases treated by glucocorticoids (mean age, 8 years; 50.2% boys; 73.8% white). Researchers asked children or caregivers about the presence of any back pain in the preceding 3 months; total calcium and vitamin D intake were assessed via food frequency questionnaire. All children underwent DXA imaging to assess lumbar spine BMD. Vertebral fractures were assessed on lateral thoracolumbar spine radiographs. Researchers used logistic regression analysis to estimate the relationship between prevalent vertebral fractures and back pain, lumbar spine BMD, male sex, percent cortical area and vitamin D intake.
Within the cohort, 44 children had prevalent vertebral fractures. Of those, 29 children had leukemia, nine had rheumatologic disorders and six had nephrotic syndrome.
Compared with children without fractures, those with prevalent vertebral fractures had a lower mean lumbar spine BMD z score (–1.7 vs. –0.8; P < .01) and a lower percent cortical area z score (0.1 vs. 0.3; P = .04) and were more likely to report back pain (52.3% vs. 19.2%; P < .01).
In logistic regression analysis, the OR for prevalent vertebral fracture per reduction in z score unit of lumbar spine BMD was 1.9 (95% CI, 1.5-2.5), with an area under the receiver operating characteristic curve of 0.7 (95% CI, 0.6-0.79), and an optimal BMD z score cutoff of –1.6.
Case identification using low BMD alone (z score < –1.6) or back pain alone gave similar results for sensitivity (55% and 52%, respectively), specificity (78% and 81%), positive predictive value (24% and 25%) and negative predictive value (93% and 93%).
Using low BMD plus back pain produced lower sensitivity (32%), higher specificity (96%), higher positive predictive value (47%) and similar negative predictive value (92%). The approach using low BMD or back pain had the highest sensitivity (75%), lowest specificity (64%), lowest positive predictive value (20%) and highest negative predictive value (95%).
“The most common approach is to do spine radiographs only if a patient either has low BMD or back pain,” the researchers wrote. “Our results show that either of these two approaches on their own will generate results similar to each other. Each will pick up just over half of the subjects with prevalent vertebral fracture (sensitivities of 52% and 55%) and, in a population with a prevalence of vertebral fracture similar to our study cohort, would require spine radiographs in about one-quarter of patients (23% and 25%), leading to detection of one patient with prevalent vertebral fracture for every four (4 and 4.2) subjects having radiographs.”
The researchers noted that many vertebral fractures will spontaneously heal due to modeling during subsequent growth; however, grade 2 and grade 3 fractures are less likely to resolve, and their detection may serve as an indication for osteoporosis therapy. – by Regina Schaffer
Disclosures: The authors report no relevant financial disclosures.
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