COMPARISON OF SEMIQUANTITATIVE VISUAL AND QUANTITATIVE MORPHOMETRIC ASSESSMENT OF PREVALENT AND INCIDENT VERTEBRAL FRACTURES IN OSTEOPOROSIS

The assessment of radiographs for vertebral fractures is important in the clinical evaluation of patients with suspected osteoporosis, in th e epidemiological evaluation of elderly populations, and in clinical t rials of osteotrophic drugs. The purpose of this study is to compare v isual semiquantitative (SQ) approaches and quantitative morphometric a pproaches for assessing prevalent and incident vertebral fractures in postmenopausal osteoporosis. We analyzed lateral thoracolumbar spine r adiographs (baseline and similar to 3.5 year follow-up) of 503 women ( age greater than or equal to 65) randomly selected from the Study of O steoporotic Fractures (SOF) population. SQ assessment by an experience d radiologist graded vertebral fractures from 0 (normal) to 3 (severe) . Incident fractures by SQ were defined as an increase of greater than or equal to 1 grade on follow-up radiographs. Trained research assist ants visually triaged women as normal, uncertain, or probably fracture d and visually nagged vertebrae with moderate/severe (grade greater th an or equal to 2) prevalent fractures or with any (grade greater than or equal to 1 change) incident fracture. The radiographs were also dig itized by research assistants, and quantitative morphometry (QM) was u sed to classify vertebral deformities at several cut-offs based on sta ndard deviation (SD) reductions in height ratios from normal means, e. g., QM greater than or equal to 3 SD. Incident fractures by QM were de fined as a decrease in height of more than 15% (QM15) on follow-up rad iographs. Finally, a combination of these methods was used to detect m oderate/severe prevalent fractures and any grade of incident fractures . In the overall analysis, the prevalence of fractures varied from 14 to 33% and the incidence from 5 to 10% by woman, depending upon the me thod and cut-off criteria. In the detailed analysis, considering visua lly triaged uncertains as abnormal, triage by research assistants dete cted 97.0% (163/168) of women with SQ grade greater than or equal to 1 fractures and 100% (70/70) with SQ grade greater than or equal to 2 f ractures. Visual flagging by research assistants detected 88.5% (108/1 22) of SQ greater than or equal to 2 prevalent fractures (kappa score, kappa = 0.82) and 85.2% (52/61) of SQ incident fractures (kappa = 0.7 9). QM greater than or equal to 3 SD detected 37.9% (141/372) of SQ gr eater than or equal to 1 prevalent fractures (kappa = 0.51) and 79.5% (97/122) of SQ greater than or equal to 2 prevalent fractures (kappa = 0.68), plus 18 vertebrae without SQ fractures. QM15 detected 59% (36/ 61) of SQ incident fractures (kappa = 0.70), plus five vertebrae witho ut SQ incident fractures. The combination assessment detected 92% (112 /122) of SQ greater than or equal to 2 prevalent fractures (kappa = 0. 76) and 84% (51/61) of SQ incident fractures (kappa = 0.91). The preci sion errors of QM vertebral height measurements (baseline versus follo w-up) ranged from 2.71 to 2.92%. Nevertheless, excluding the 5719 vert ebrae that were clearly normal by morphometry, i.e., within 2 SD of th e normal means at both baseline and follow-up, two-thirds (358/556) of the remaining vertebrae changed classification by at least 1 SD categ ory. Visual triage and visual flagging by research assistants appear t o be highly effective methods for vertebral fracture assessment in ost eoporosis, potentially reducing the number of false-positive and false -negative fractures detected by QM, at least relative to SQ by the rad iologists.There is higher concordance among the visual approaches stud ied than between the visual SQ and quantitative morphometric approache s, with QM having limited ability to detect mild fractures but good ab ility to detect moderate/severe fractures, as classified by SQ. Use of a combination of sensitive qualitative and quantitative criteria, wit h adjudication by an experienced radiologist, is feasible and draws up on the relative strengths of each of the methods. Quantitative morphom etry should not be performed in isolation, particularly when applying highly sensitive morphometric criteria at low threshold levels, withou t visual assessment to confirm the detected prevalent or incident vert ebral deformities as probable fractures.