The prevention and management of osteoporosis
Consensus statement		 Contents list

4. What diagnostic evaluations are needed in patients with presumed osteoporosis?

THE CHOICE of appropriate diagnostic technique is influenced by the aetiology of the presumed osteoporosis. Depending on the clinical assessment, one or more of the following diagnostic procedures will be required.

 

Radiographic assessment

X-rays will usually be necessary to confirm a fracture but are not suitable for use in the diagnosis of low bone density.

 

Bone densitometry

As discussed under Question 3, this is currently the single best in-vivo estimate of bone strength. Densitometry technology has advanced to such a degree that it measures apparent bone mineral density with acceptably high accuracy and precision. It is now relatively widely available and inexpensive. Dual energy x-ray absorptiometry (DXA) can provide a rapid assessment of both whole body and regional bone mass (and calculated "areal density"). Quantitative computerised tomography (QCT) directly measures trabecular bone density, but with greater radiation dose, imprecision and expense, and is therefore not the preferred approach. However, QCT is useful when DXA is not readily available (e.g., in some rural areas).

Due to differences in both hardware and software, bone density values obtained from instruments produced by different manufacturers cannot be compared directly. Therefore, for the diagnosis of low bone density, the individual's absolute value derived from any given instrument must be related to the sex-specific reference range derived from the same model instrument. Similarly, for meaningful detection of change over time, serial measurements in the same individual should be performed on the same instrument.

Regional bone mass measurements can be readily performed on skeletal sites commonly involved in osteoporotic fracture (e.g., lumbar spine, forearm, proximal femur). In older individuals, caution is required in assessing bone mass in the lumbar spine, where there may be a partial or complete compression fracture, vascular calcification or degenerative spinal disease. Greater diagnostic accuracy may result from bone mass measurements at more than one skeletal site.

At present ultrasound measurement of bone strength lacks acceptable measurement precision and long-term stability to be recommended for use in diagnosis of osteoporosis. The results of further prospective studies are awaited.

 

Pathology testing

The extent to which investigations are necessary is determined by the clinical picture, but the index of suspicion for secondary causes of osteoporosis should increase in patients with severe bone loss for age (e.g., bone density lower than 2.0 standard deviations below the age-related mean).

Extensive pathology testing is not required. However, specific pathology tests should be considered in a range of conditions. Relevant initial tests include adjusted total calcium, total alkaline phosphatase, creatinine, full blood count and erythrocyte sedimentation rate.

Further testing (guided by clinical indicators) includes:

  • 25-hydroxyvitamin D (vitamin D deficiency);

  • thyroid function tests (hyperthyroidism or long term thyroid hormone therapy);

  • sex steroids (e.g., testosterone in hypogonadal men);

  • intact parathyroid hormone (hyperparathyroidism);

  • liver function tests (in people possibly consuming excessive amounts of alcohol); and

  • protein electrophoresis (multiple myeloma).

Next: Is screening of the general population or high risk groups for osteoporosis effective or cost-effective?

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©1997 Medical Journal of Australia.