In thalassemic patients individual values of BMD measured by traditional DEXA are lower than those determined by QCT. The reason for this discrepancy is still controversial.
Aim: To investigate bone features in a large group of thalassemic patients, compared with patients with anorexia nervosa, also characterized by precocious osteoporosis.
Study design: Forty-six adult thalassemic subjects and 25 anorectic women were studied. In all patients lumbar BMD was determined by DEXA and standard QCT. In a subset of 22 thalassemic and 13 anorectic patients, a modified QCT was also performed: this technique allows to include the measurement of the cortical component of the vertebra, at variance with standard QCT which measures volumetric BMD in a limited trabecular portion.
Results: In the whole group of thalassemic patients the mean lumbar Z-score measured by QCT was significantly higher than that measured by DEXA. On the contrary, in anorectic women the mean Z-score values measured by the two techniques were not significantly different. While in thalassemic patients the correlation between QCT and DEXA values was weakly positive, in anorectic women the same correlation was highly significant. Interestingly, when considering the BMD values determined by the modified QCT, these correlations were highly significant in both groups.
Conclusions: (a) Our data point to the peculiarity of bone disease in thalassemia in comparison with other forms of juvenile osteoporosis. (b) In thalassemic patients the degree of lumbar osteopenia appears to be more severe when estimated by DEXA compared to standard QCT; however, the correlation between the two techniques improves when including the whole vertebra using QCT measurement. (c) The discrepancy between the two methods might be accounted for by a greater involvement of cortical bone in thalassemia. (d) Standard QCT seems to underestimate the degree of bone damage in this haematological condition.