The role of using different reference population in the prevalence of low BMD in the thalassemia patients

Prevalence of osteoporosis reported as high as 50% in thalassemia major patients. We compared bone density (BMD) of our patients with results of bone densitometry of participants of a national study, to find if BMD diagnosis is ethnicity sensitive or not.

In 177 adult beta thalassemia major patients and 490 normal subjects of 20-39 y/o range, dual-energy X-ray absorptiometry of the spine and femur performed. Normal subjects participated in Iranian Multi-center Osteoporosis Study (IMOS). Mean and standard deviation of normal ones achieved and Z-score of patients re-calculated based on normal Iranians. As BMD of normal participants and patients performed by devices of different brands, analyses done based on calculated standard BMD of all participants.

BMD of patients was significantly lower than normal participants (P value <0.001). Frequency of Z-score ≤-2 found in 52% and 56% of patients in femur and spine regions, respectively. New Z-score of patients according to Iranian normal populations calculated. Frequency of this new Z-score ≤-2 found in 16% and 72% of patients in femur and spine regions, respectively.

We think in secondary osteoporosis, may be other cut-off points, especially according to BMD of normal population of that geographical region are needed.