Diagnostic Tests For Osteoporosis

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[edit] Diagnostic Tests For Osteoporosis

With primary osteoporosis cases simple blood tests like calcium, phosphate, alkaline phosphatase levels, red blood cell sedimentaion rate and serum electophoresis would all be normal. Type I osteoporosis (click on "causes of osteoporosis" , see table) would show elevated FSH/LH levels, low estradiol in women and low testosterone in males. Male and female hormone deficiency (=hypogonadism) is found in this type.

Type II osteoporosis is usually associated with vitamin D deficiency and we know from research papers that there is a lowered number of bone building cells in the bone, which leads to a dysbalance between bone production and bone turnover with an overall net bone loss. The ultimate test for determining the amount of bone mass loss is with the help of dual X-ray absorptiometry (for short: DXA).

This DXA scan is done easily at the X-ray department (Ref.1). The results are scored as outlined in the beginning of the chapter, expressed as standard deviations below the norm of a 35-year old control person matched for sex and race. This bone density test provides the physician a powerful tool to assess the risk for a fracture in the near future.

This relationship would be similar to measuring blood pressure and predicting how likely it would be for the patient to get a stroke. It has been determined in a group of patients with osteoporosis that the difference in probability between the lower density and higher density patients on the DXA test to develop a hip fracture was 8.5-fold higher (Ref.1).

In secondary osteoporosis blood tests would be ordered that would help in distinguishing between the specific hormone imbalance listed in the table under this link (click on "causes of osteoporosis" ,see table). A positive history, for instance, of celiac disease would likely lead to a referral of the patient to the gastroenterologist for a work-up. A rheumatologist might be needed in the case of a patient with an underlying rheumatological disease such as rheumatoid arthritis or ankylosing spondylitis.

A suspicion for cancer would trigger the physician to order a nuclear medicine bone scan, other imaging techniques and other blood tests. Finally, a history of drug use should be taken as they can interfere with bone metabolism. For instance, prednisone side effects for asthma or a rheumatic disease includes osteoporosis; and alcohol and smoking are also powerful negative factors as was mentioned above.

Here is a summary in tabular form of the tests that are done (Ref. 1 and 2) to investigate for osteoporosis.

Diagnostic tests for osteoporosis
Tests:	Comments:
X-rays	requires 30% bone loss to show as osteopenia; good for compression fractures of vertebral bones or fractures of trabecular bone
DXA (dual X-ray absorptiometry)	the gold standard to measure bone density
serum calcium	rule out hyperparathyroidism (if elevated measure parathyroid hormone)
serum protein electrophoresis	rule out multiple myeloma (if positive, check urine for Bence-Jones proteine)
T4, TSH	rule out hyper- or hypothyroidism
serum cortisol	rule out Cushing syndrome
serum testosterone	rule out malfunction of testicles
FSH, LH	in women, rule out premature menopause
indicators of bone turnover (not routinely used)	special tests like technetium-99m methylene diphosphonate etc. can be utilized
bone marrow biopsy	distinguishes between osteomalacia (vitamin D deficiency) and osteoporosis

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References:

1. ABC of rheumatology, second edition, edited by Michael L. Snaith M.D., BMJ Books, 1999.

2. The Merck Manual, 7^th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 57.

3. B. Sears: "The age-free zone".Regan Books, Harper Collins, 2000.

4. B. Sears: "Zone perfect meals in minutes". Regan Books, Harper Collins, 1997.

5. Goldman: Cecil Textbook of Medicine, 21st ed.(©2000)W.B.Saunders

6. Ferri: Ferri's Clinical Advisor: Instant Diagnosis and Treatment, 2004 ed., Copyright © 2004 Mosby, Inc.

7. Rakel: Conn's Current Therapy 2004, 56th ed., Copyright © 2004 Elsevier