Osteoporosis is assesed, according to WHO criteria, as BMD (bone mineral density). So called T-score is a representation
of patient's BMD expressed as number of standard deviations below or above
mean BMD of the young adult.
T-score values below 2.5 SD are defined as characteristic of osteoporosis.
Values between -1 SD and -2.5 SD are defined as osteopenia?.