ASSESSMENT OF OSTEOPENIA FROM SPINE RADIOGRAPHS USING 2 DIFFERENT METHODS - THE CHINGFORD STUDY

Two methods for diagnosing radiological osteopenia in thoracic (TS) an d lumbar (LS) spine radiographs were assessed: a subjective convention al method (A) and a semiquantitative method (B), by comparing them wit h bone mineral density (BMD) measured by dual energy X-ray absorptiome try (DEXA), in a population of ''normal'' women aged 45-70 years (n=81 8). For both methods there was good intraobserver and interobserver re producibility. BMDs were significantly lower with increasing radiologi cal osteopenia grades (p<0.001), and remained lower after adjustment f or age and body mass index (p<0.01). The proportion of subjects with D EXA-defined osteoporosis rose with increasing radiological osteopenia grades for both methods. The worst osteopenia categories identified 29 .7-55.3% of women with DEXA-defined osteoporosis, compared with 6.1-11 .7% in the ''normal'' categories. Both methods, however, showed a larg e degree of overlap of BMDs between the various radiological osteopeni a grades. The sensitivity and specificity of method A in diagnosing os teoporosis were 45.3% and 78.4%, respectively, for the TS and 19.0% an d 94.3%, respectively, for the LS. For method B the sensitivities and specificities were 8.8% and 96.1%, respectively (TS), and 10.2% and 95 .6%, respectively (LS). Although both methods have poor sensitivities, ''definite'' or ''high'' grade osteopenia should be an indication for bone densitometry. The high specificities suggest that a ''normal'' ( no osteopenia) X-ray is unlikely to have a significantly low BMD.