Influence of baseline deformity definition on subsequent vertebral fracture risk in postmenopausal women

Introduction: Approaches for recognizing vertebral fractures remain controversial. Methods: An age-stratified population sample of 512 postmenopausal women was followed with serial radiographs for up to 12 years (4455 person-years). Results: 112 women experienced a new vertebral fracture (20% reduction in any vertebral height from baseline) within this study period, for an annual age-adjusted (to US white women ≥50 years of age in 2000) incidence of 23 per 1000. Depending on the morphometric definition used, the prevalence of vertebral deformities at baseline ranged from 3 to 90%. A recent method to standardize vertebral heights produced the best agreement with a qualitative clinical reading of the films (kappa (κ), 0.53). Almost all of the different baseline definitions predicted future vertebral fractures, but most of the predictive power was attributable to the severe (e.g., 4 SD) deformities included within more generous (e.g., 3 SD) classifications. Whereas the generous definitions were more sensitive, and the restrictive ones more specific, their overall abilities to predict a new vertebral fracture were roughly comparable as evaluated by the c-index (analogous to the area under an ROC curve). Conclusion: This result suggests that the choice of a morphometry definition depends on the particular application and, in particular, on whether it is more important to maximize sensitivity or specificity.