Central  South  Dakota  Medical News
The Clinical View
by Phillip Hoffsten
25 August 2004

WHAT IS A BONE MINERAL DENSITY TEST?

     The lady was 54 years old and was almost dragged to the clinic by her daughter who was a nurse.  The daughter had been telling mom that a medical checkup was needed even though mom was “feeling good”.  Mom felt that there was nothing wrong with her.  But to pacify her daughter, she finally came to be evaluated.

     The patient offered no complaints or symptoms.  She did acknowledge that she smoked a pack of cigarettes per day and had for more than 30 years.  She indicated that she slept well, was only slightly overweight at 140 lbs and 5 feet 6 inches tall.  She said she ate what she liked and didn’t try to follow any particular diet.  Specifically she didn’t drink milk because milk or milk products seemed to cause diarrhea.  She had a sedentary job in a clerical capacity and made no effort at an exercise program. She indicated that occasionally she would go walking with friends or on shopping trips and had no difficulty with keeping up when walking.

     The family history indicated that one maternal aunt had had a breast cancer but there were no other illnesses reported in her family of two brothers and four sisters.  Several blood tests were ordered including a cholesterol panel, electrocardiogram and chest film were also ordered.  The chest film showed early changes of emphysema but no other abnormalities were noted.  Mammography was suggested to screen for breast cancer especially in light of her positive family history in a female blood relative.  The patient agreed to all of these suggestions.

     It was then suggested that she have a bone mineral density test  (DEXA) done in light of her history of low calcium intake on no supplement and her ongoing history of cigarette abuse.  Cigarette smoking antagonizes Vitamin D and decreases calcification of the skeleton.  Both of the above factors can be strong contributors to the development of a disease called osteoporosis.  But the patient wanted a more detailed description of what a bone mineral density test was and what it would do for her.

     It was explained that the amount of mineral and strength in a person’s bones peaks at 22 to 28 years of age.  How high that peak will be depends upon the person’s physical activity and how much calcium they take in during their youth.  It is the reason that it is so important for our children to be drinking milk instead of carbonated beverages.  After age 28, the bone mineral slowly dissolves out of our bones over the rest of our lives.  As the bone mineral dissolves out, the bones become weaker and fractures become more likely.  This is especially true in individuals who fall and break their hip, their spine or their wrist.  The likelihood that a fracture will occur is directly related to the amount of calcium mineral that is in the bone.  The less calcium in the bone, the more likely it is to fracture.

     The lady then asked how an x-ray could measure the amount of calcium in a person’s bone.  It was explained that x-rays can be thought of rather like a light.  The heavier your curtains, the less light that comes through.  The more mineral in your bones, the less x-ray will come through to the x-ray plate.  By measuring the amount of mineral in many, many bones and how well the x-ray penetrated those bones, we now have an excellent method for estimating how much calcium is in a person’s bones.

     The test is done by having the person lie on an examining table and x-rays are passed through the spine and through the hips.  These are the two most dangerous areas for fractures to occur.  Through a computer calculation, the amount of calcium in that person’s bones can then be estimated with remarkable accuracy.  Another advantage of this examination is that it can be used serially to determine if the problem is getting better or getting worse.

     The lady’s last question was very perceptive on her part.  She wanted to know what could be done if the bone mineral density was to low and fractures were likely.  It was explained that there are multiple medications now available that can help remineralize bones that have been washed out.  The most potent and effective are a family of drugs called bisphosphonates with the trade names of Fosamax and Actonel.  These medications are taken on once a week basis on an empty stomach in the early morning hours before breakfast.  Breakfast must be delayed at least a half an hour after the pill is taken.  The side effect profile for this medication is remarkably low and the effectiveness is remarkably good.  Within one year of starting this medication, the incidence of hip fractures decreases substantially and the bone mineral density will increase between 2 and 8%.

     After all of the above discussion, the lady did agree to go ahead and have her bone mineral density checked.  She had passed her menopause three years earlier and with her history of a low calcium intake and cigarette abuse, it was seen that she had a significantly decreased bone mineral density.  Based upon all of the discussions above and more yet when the results of her test returned, she was started on a medication to protect her bones.  Additional suggestions were to take 1500 mg of calcium per day and 800 units of Vitamin D per day.  The Vitamin D is a critical agent for having the person absorb calcium in their diet.  Without Vitamin D, calcium in a diet is simply passed out in the stool and wasted.  It was also recommended that she start an exercise program of walking three miles per day.  She bought a step-meter to see how far she walked each day and she found that it was only a mile and a half on the average.  This is true for most people with office jobs.  A program of at least a half hour walk sometime during the day is needed to reach three miles a day.  Lastly, it was suggested that she stop her cigarette habit and she pointed out how hard that was to do.

     Next year another bone mineral density test will be done to see if there has been improvement in her bone mineral density.  The healthcare professionals at your local clinic are aware of the above considerations and how important they are.  A fractured hip in an elderly individual is associated with a very poor chance of rehabilitation and a substantial mortality.  Preventing hip fractures through the early maintenance of bone mineral density is an important part to long-term quality of life.