Algorithm-based qualitative and semiquantitative identification of prevalent vertebral fracture: agreement between different readers, imaging modalities, and diagnostic approaches

Abstract

We compared SQ and ABQ diagnosis of VF imaged by radiography and X-ray absorptiometry. Mild ABQ VF had stronger associations with osteoporosis than mild SQ VF. Interobserver agreement (radiographic diagnosis) was better for ABQ.

Introduction: Vertebral fracture (VF) assessment from images acquired by X-ray absorptiometry (VFA) is often based on a semiquantitative approach (SQ); prevalent VF is identified if vertebral height appears reduced by >20%. Algorithm-based qualitative definition of osteoporotic VF (ABQ) requires evidence of endplate depression, and there is no threshold for reduction in vertebral height. The aims of this study were to (1) compare the prevalence of VFs; (2) compare the characteristics of women with and without VFs; (3) compare interobserver agreement; and (4) compare agreement between methods and imaging modalities for ABQ and SQ definitions of VFs.

Materials and methods: Spine radiographs and absorptiometry images for 203 elderly women were assessed using ABQ (readers ABQ-1 and ABQ-2). These readings were compared with SQ assessments (readers SQ-1 and SQ-2) of the same images performed in a previous study. Agreement between readers and methods was assessed by kappa (kappa) statistics.

Results: The prevalence of VF was 15-18% (radiography) and 12-24% (VFA) for ABQ and SQ, respectively. Women with ABQ or SQ fractures were older and had lower BMD than those without fracture (p < 0.01). Mild ABQ (but not SQ) VF was associated with low BMD. Kappa scores for interobserver agreement for radiography and VFA, respectively, were as follows: ABQ, kappa = 0.74 (95% CI, 0.60, 0.87) and 0.65 (95% CI, 0.48, 0.81); SQ, kappa = 0.53 (95% CI, 0.46, 0.60) and 0.51 (95% CI, 0.44, 0.58). For agreement between ABQ-1 and SQ-1, kappa = 0.55 (95% CI, 0.39, 0.72) for radiography and 0.41 (95% CI, 0.25, 0.58 for VFA.

Conclusions: The prevalence of radiographic VF identified by ABQ and SQ was similar, but on VFA was 50% higher for SQ. Mild ABQ VF was associated with low BMD. Interobserver agreement for radiographic diagnosis was significantly better for ABQ than for SQ. Agreement between ABQ and SQ was moderate.