Exclusion of focal vertebral artifacts from spine bone densitometry and fracture prediction: a comparison of expert physicians, three computer algorithms, and the minimum vertebra.

UNLABELLED

Expert physicians and automated methods for the exclusion of vertebral levels in DXA scans containing focal artifacts were compared. All methods of vertebral exclusion led to a small improvement in fracture prediction. Computer algorithms performed at least as well as physicians.

INTRODUCTION

Lumbar spine DXA is often confounded by focal artifacts. Clinical rules and automated methods for vertebral exclusion have been proposed, but their concordance, effect on diagnosis, and fracture prediction is unknown.

MATERIALS AND METHODS

We analyzed clinical DXA scans of the lumbar spine (20,478 women and 1534 men) performed from 1998 to 2002 (Province of Manitoba, Canada). Longitudinal health service records were assessed for the presence of nontrauma fracture codes after BMD testing. The effect of vertebral exclusions by expert physicians and several automated methods on diagnosis and prediction of incident fractures was compared.

RESULTS

Vertebral exclusions were reported by physicians in over one quarter of the scans (31% of women and 29% of men). All methods of vertebral exclusion significantly decreased the mean spine T-score and increased the proportion of women designated as osteoporotic. kappa values and ROC area under the curve (AUC) for physician-computer agreement in the identification of abnormal scans indicated fair to moderate agreement in both women and men. Compared with no vertebral exclusions, a small increase in the hazard ratio and AUC for spine fracture and osteoporotic fracture prediction was seen after physician and computer exclusions. Compared with physician exclusions, AUC for prediction of osteoporotic fractures in men increased significantly with one computer algorithm (p = 0.004). The minimum vertebral T-score enhanced fracture prediction compared with no exclusions but approximately doubled the prevalence of osteoporotic categorization.

CONCLUSIONS

We observed fair to moderate agreement between the physician and computer methods for vertebral level exclusion. All methods of vertebral exclusion led to a small improvement in fracture prediction using the lumbar spine measurement. The automated algorithms performed at least as well as physicians when fractures were used as the endpoint.