Can secondary osteoporosis be identified when screening for osteoporosis with digital X-ray radiogrammetry? Initial results from the Stockholm Osteoporosis Project (STOP).

OBJECTIVES: To identify causes of low age-adjusted bone mass at digital X-ray radiogrammetry (DXR) in individuals attending an osteoporosis screening program.

STUDY DESIGN: In a descriptive observational cohort study, women aged 40-75 years who attended a general mammography screening program had their bone mass investigated with DXR and answered a questionnaire regarding several clinical risk factors for osteoporosis. Each month the 2% with the lowest Z-scores were selected for further clinical examination with DXA of the hip and lumbar spine and pre-defined blood tests.

MAIN OUTCOME MEASURE: Causes of secondary osteoporosis determined by clinical and laboratory evaluation.

RESULTS: 14,783 women attended mammography screening and had their bone mass evaluated. In total, 327 women had a low DXR BMD and 281 accepted further DXA examination. Of these, 93 (33.1%) had osteoporosis. The diagnosis was new in 79 cases (84.9%) and in 32 (34.4%) a potential underlying cause was identified. Primary hyperparathyroidism was found in 8.6% and secondary hyperparathyroidism in 13.5%. Several self-reported risk factors for osteoporosis, including rheumatic disease, insulin-treated diabetes, cortisone treatment, smoking, reduced mobility, hyperparathyroidism, and malabsorption, were significantly more common among those selected for DXA referral than in the total cohort. For example, rheumatic disease and insulin-treated diabetes were reported 3.4 and 2.3 times as often, respectively.

CONCLUSION: The prevailing potential cause of secondary osteoporosis according to DXR was primary and secondary hyperparathyroidism. Most of the women with these conditions were previously undiagnosed, indicating that further follow-up of patients with low age-adjusted DXR BMD is justified.