Indications for BMD testing
The ISCD's indications for BMD testing remain for women age 65 and older. For postmenopausal women younger than age 65, a BMD test is indicated if they have a risk factor for low bone mass, such as 1) low body weight, 2) prior fracture, 3) high-risk medication use, or 4) a disease or condition associated with bone loss. A BMD test also is indicated for women during the menopausal transition with clinical risk factors for fracture, such as low body weight, prior fracture, or high-risk medication use. Interestingly, the ISCD recommendation for men is similar but uses age 70 for this group.
In addition, the ISCD recommends BMD testing in adults with a fragility fracture, with a disease or condition associated with low bone mass, or taking medications associated with low bone mass, as well as for anyone being considered for pharmacologic therapy, being treated (to monitor treatment effect), not receiving therapy in whom evidence of bone loss would lead to treatment, and in women discontinuing estrogen who should be considered for BMD testing according to the indications already mentioned.
Sites to assess for osteoporosis. The World Health Organization international reference standard for osteoporosis diagnosis is a T-score of -2.5 or less at the femoral neck. The reference standard, from which the T-score is calculated, is for white women aged 20 to 29 years of age from the database of the Third National Health and Nutrition Examination Survey. Osteoporosis also may be diagnosed in postmenopausal women if the T-score of the lumbar spine, total hip, or femoral neck is -2.5 or less. In certain circumstances, the 33% radius (also called the one-third radius) may be utilized. Other hip regions of interest, including Ward's area and the greater trochanter, should not be used for diagnosis.
The skeletal sites at which to measure BMD include the anteroposterior of the spine and hip in all patients. In terms of the spine, use L1-L4 for spine BMD measurement. However, exclude vertebrae that are affected by local structural changes or artifact. Use 3 vertebrae if 4 cannot be used, and 2 if 3 cannot be used. BMD-based diagnostic classification should not be made using a single vertebra. Anatomically abnormal vertebrae may be excluded from analysis if they are clearly abnormal and nonassessable within the resolution of the system, or if 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 are used to derive the T-score.
For BMD measurement at the hip, the femoral neck or total proximal femur—whichever is lowest—should be used. Either hip may be measured. Data are insufficient on whether mean T-scores for bilateral hip BMD should be used for diagnosis.
Terminology. While the ISCD retains the term osteopenia, the term low bone mass or low bone density is preferred. People with low bone mass or density are not necessarily at high fracture risk.
Concerning BMD reporting in women prior to menopause, Z-scores, not T-scores, are preferred. A Z-score of -2.0 or lower is defined as "below the expected range for age"; a Z-score above -2.0 is "within the expected range for age."
Use of serial BMD testing
Finally, regarding serial BMD measurements, such testing in combination with clinical assessment of fracture risk can be used to determine whether treatment should be initiated in untreated patients. Furthermore, serial BMD testing can monitor a patient's response to therapy by finding an increase or stability of bone density. It should be used to monitor individuals following cessation of osteoporosis drug therapy. Serial BMD testing can detect loss of bone density, indicating the need to assess treatment adherence, evaluate possible secondary causes of osteoporosis, and possibly re-evaluate therapeutic options.
Intervals between BMD testing should be determined according to each patient's clinical status. Typically, 1 year after initiating or changing therapy is appropriate, with longer intervals once therapeutic effect is established.
WHAT THIS EVIDENCE MEANS FOR PRACTICE
Patients commonly ask for BMD testing and ObGyn providers commonly order it. Understanding appropriate use of BMD testing in terms of who to scan, what sites to evaluate, when there may be spurious results of vertebrae due to artifacts, avoiding T-scores in premenopausal women in favor of Z-scores, understanding that low bone mass is a preferred term to osteopenia, and knowing how to order and use serial BMD testing will likely improve our role as the frontline providers to improving bone health in our patients.
Patients commonly ask for BMD testing and ObGyn providers commonly order it. Understanding appropriate use of BMD testing in terms of who to scan, what sites to evaluate, when there may be spurious results of vertebrae due to artifacts, avoiding T-scores in premenopausal women in favor of Z-scores, understanding that low bone mass is a preferred term to osteopenia, and knowing how to order and use serial BMD testing will likely improve our role as the frontline providers to improving bone health in our patients.
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