Z score in bone mineral density measurement

Bone mineral density may be quoted as the number of standard deviations from the age-related mean. This is the Z score, and is a comparison with the bone density of people of the same age and sex as the patient. A negative Z-score of -2.5 or less should raise suspicion of a secondary cause of osteoporosis.

Although this does not allow diagnosis of osteoporosis according to WHO guidelines which quote T scores, it does give the physician some idea of a patient's risk in relation to other patients of the same age.

Reference

1. Diamond T. Bone mineral density: testing for osteoporosis. Aust Prescr. 2016 Apr;39(2):35-9