Osteoporosis: From concepts to T scores and now absolute fracture risk

The definition of osteoporosis has always been challenging. Historically the clinical definition could only be based on the presence or occurrence of an osteoporotic fracture. However waiting for a fracture to occur before making a diagnosis has limitations, not least that high risk individuals cannot be identified for treatment prior to fracture. With the availability of bone density measurements, the definition moved to the use of T-scores. Whilst widely used, this approach has limitations that include low sensitivity and not taking into account other variables that influence bone strength and extra-skeletal risk factors. In view of the limitations of using T scores in isolation, there has been a move towards assessment of individualised risk that incorporates multiple risk factors (with or without bone density measurement) to help predict future fracture risk. This approach potentially allows identification and treatment of individuals at high risk of fracture, the condition that needs to be treated as opposed to treating low bone density. Indeed bone density (where measured) becomes one of the many risk factors without a threshold interpretation for any given value. Numerous tools are available that have varying sensitivity, specificity, utility, applicability to, and that have been validated for any given population. Of the available tools, the World Health Organisation Fracture Risk Assessment Tool (FRAX) calculator has been extensively studied. It is available more widely, with country specific utility with and without bone density measurements, which is important in regions with scarce access to bone densitometry. FRAX is the only tool available that is India specific.