Endocrine Abstracts

Background: Bone mineral density (BMD) measurement is an important tool for fracture risk assessment, but should be used with awareness of its performance and analysis pitfalls.

Case Presentation: A 59-year-old patient underwent her first densitometry as part of a routine medical check-up. She had no previous fractures and no risk factors that could impair bone health. The results showed that her BMD was in the range of low bone mass. Four years later, densitometry was performed again with the same device, but without calibration for the least significant change. Based on the very low T-score of -3.7 at the lumbar spine, osteoporosis was diagnosed and denosumab therapy was initiated. There were no newly acquired comorbidities, and secondary causes of osteoporosis were not investigated. The third densitometry was performed a year later, at the age of 64, before she came to our clinic. This time, a lumbar spine T-score of -2.3 was obtained with a different device. This was again discordant to the second densitometry, as such a rapid improvement after the administered therapy would not be expected. We reviewed all three densitometry reports and found that her second densitometry, which showed osteoporosis, had incorrect vertebral labelling: Th12-L3 were measured instead of L1-L4. Even without taking into account that she had previously received three denosumab doses, the Fracture Risk Assessment Tool was low and estimated 5.1% risk of major osteoporotic and 0.5% risk of hip fractures. It was evident that she did not need osteoporosis treatment. Although the risk of rebound effects after short-term denosumab therapy and low C-telopeptide was low, we gave her a dose of zoledronate seven months after the last denosumab application.

Conclusions: Justified indications for BMD (re)testing, careful analysis of results and interpretation of reports are mandatory to avoid overdiagnosis and misdiagnosis of osteoporosis, which could lead to ineffective, costly, and even damaging consequences.