Table of Contents
DEXA Criteria for Diagnosis
- The WHO international reference standard for osteoporosis diagnosis is a T-score of -2.5 or less at the femoral neck.
- Osteoporosis may be diagnosed in postmenopausal women and in men age 50 and older if the T-score of the lumbar spine, total hip, or femoral neck is -2.5 or less.
- In certain circumstances the distal radius (also called 1/3 radius) may be utilized.
- Other hip regions of interest, including Ward’s area and the greater trochanter, should not be used for diagnosis.
Skeletal sites to measure
- Measure BMD at both the PA spine and hip in all patients
- Forearm BMD should be measured under the following circumstances:
- Hip and/or spine cannot be measured or interpreted.
- Very obese patients (over the weight limit for DXA table)
- Use PA L1-L4 for spine BMD measurement
- Use all evaluable vertebrae and only exclude vertebrae that are affected by local structural change or artifact. Use three vertebrae if four cannot be used and two if three cannot be used
- BMD based diagnostic classification should not be made using a single vertebra.
- If only one evaluable vertebra remains after excluding other vertebrae, diagnosis should be based on a different valid skeletal site
- Anatomically abnormal vertebrae may be excluded from analysis if:
- They are clearly abnormal and non-assessable within the resolution of the system; or
- There is more than a 1.0 T-score difference between the vertebra in question and adjacent vertebrae
- When vertebrae are excluded, the BMD of the remaining vertebrae is used to derive the T-score
- The lateral spine should not be used for diagnosis, but may have a role in monitoring
- Use femoral neck, or total proximal femur whichever is lowest.
- BMD may be measured at either hip
- There are insufficient data to determine whether mean T-scores for bilateral hip BMD can be used for diagnosis
- The mean hip BMD can be used for monitoring, with total hip being preferred
- Use 33% radius (sometimes called one-third radius) of the non-dominant forearm for diagnosis. Other forearm ROI are not recommended.
BMD Reporting in Postmenopausal Women and in Men Age 50 and Older
- T-scores are preferred.
- The WHO densitometric classification is applicable.
BMD Reporting in Females Prior to Menopause and in Males Younger Than Age 50
- Z-scores, not T-scores, are preferred. This is particularly important in children.
- A Z-score of -2.0 or lower is defined as “below the expected range for age”, and a Z-score above -2.0 is “within the expected range for age.”
- Osteoporosis cannot be diagnosed in men under age 50 on the basis of BMD alone.
- The WHO diagnostic criteria may be applied to women in the menopausal transition.