Table 3.

SD and T-score values based on bone mass variation.

Diagnostic category	Standard deviation value (SD)	T-score
Healthy bone mass	BMD within 1 SD of the reference mean for young adults	T-score > − 1
Lone bone mass/osteopenia	BMD between 1.0 and 2.5 SD below the mean for young adults	T-score between − 1 and − 2.5
Osteoporosis	BMD of ≥ 2.5 SD below the mean for young adults	T-score < − 2.5
Severe or established osteoporosis	BMD of ≥ 2.5 SD below the mean for young adults in the presence of one or more fractures	T-score < − 2.5