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How accurate is a DEXA bone density test?

Nearly every day I see women and physicians themselves getting very worried when a woman's bone density tests show even a small 1-2% decline. Women are often told their fracture risk has greatly increased and that they should immediately begin osteoporosis drug therapy. For many women, the growing "osteoporosis fear" is fueled by small reductions in bone density. But what do these small changes really mean, and just how accurate are the DEXA bone density tests anyway?

Thanks to the excellent work of the University of Washington osteoporosis specialist, Dr. Susan Ott, we now know that the common bone density test is rather imprecise and large changes in density are needed to assure that bone loss is indeed occurring, much less significant in nature. A thoughtful scientist, Dr. Ott had 300 patients get two bone density measurements: one when they came into the room, and the second after walking around the room for a while. With this simple experiment she showed that repeat measurements on the same day may show as much as 7% difference in bone mineral density. Breaking down the data she found that while a 4-6% change in bone mineral density indicates a "probably change" it takes more than a 6% change to fully guarantee a statistically significant change in bone density.

The Better Bones perspective on bone density testing: Bone density testing can be useful, especially when spaced over many years, but small changes are not significant and certainly not a basis for beginning bone drug therapy.

Reference:

Dr. Susan Ott's website: http://courses.washington.edu/bonephys/opBMDp.html

 

We created the Osteo Blast blog as our forum to express opinions and educate the public about natural means of supporting and improving bone health and overall wellness. As part of this forum, we sometimes discuss medical issues and medications, and their effects on bone health in general. However, we cannot advise readers about specific medical issues in this forum. If you wish to obtain advice from Susan E. Brown, PhD, about your specific bone health and nutritional concerns, please visit our Consultations page. Other specific medical questions should be referred to your healthcare provider.

Comments

January 7. 2010 16:22

Hello Dr. Brown.

Hello Dr. Brown.

I am a cardiovascular nurse and an active and health conscious, almost 49 year old woman. I never smoke, I take vitamins including Calcium 1200 mg and vitamin –D 1000mg most every day, and I exercise regularly including yoga.

Last week, I had my third bone density test since 2005 and one physician told me according to the results that I have, “significant decrease in bone density in my bilateral hips”. He prescribed Fosamax.  I contacted my GYN for a second opinion and after reviewing my text results she told me that I am completely normal. To my concerns, she replied that there is a decrease in bone density but still within the normal range.

In reading this article “How accurate is a Dexa bone  density text, I am wondering if the fact that I did not work out that morning before the exam, (but afterwards) may have altered the results of my test.

Please advice,

Thank you very much,

Irma Velasquez-Kressner
New Jersey

Irma Velasquez-Kressner

January 18. 2010 20:14

Hi Irma,
Your lack of exercise before the exam should not effect the results.
Good idea to get a second opinion.  If you find at any point that you are loosing bone be sure to get a medical work-up for bone loss.  I will soon post a full discussion on the tests involved in a osteoporosis medical work-up.  Good luck, Susan E.  Brown

Susan Brown

January 26. 2010 21:48

Hi Dr. Brown, thank you for your reply.  Looking forward to reading your discussion on osteoporosis medical work-up.

I am taking my vitamin-D and Calcium more carefully than before I was wrongly diagnosis of osteoporosis and I am continue to enjoy my yoga and fitness routine.
Regards, Irma

Irma Velasquez-Kressner

April 8. 2010 12:16

Dr. Brown I am 59 year old that has a history of thyroid disease and chronic Broncheitasis. My lungs have severe damage. I have tried to take Actonal on three different occasions. It makes me very sick running fever and chills, It feels like you have the flu and can not move. My work noticed it and sent me home. I only way 91
lbs fom the complecations of the lung diseas and hyper thyroid.
I recantly had a bone density tesyt and they told me it is at the worse scale rating. I can not tolerate those chemicals, could you please advise me what I can do. Is there homophatic tratement that works?  How can I strengthen my bone mass? If I drink a lot of milk will that help or not? I am at a loss because those drugs with chemicals will kill you.  I had no energy at all while on those.
And typically I am very robust with a ton of energy even though my bones are very small. I have a very small frame so everything is over kill for me. Could you make a suggestion please.

Dawn Gable

April 8. 2010 12:24

Dr. Brown can you post answer on your web site about my issues.
I can not tolerate Actonel or Fosamax. I run fever with chills.
pain and cramps in lower legs. No energy at all. Feel very sick on drugs with no releif from day to day.
What can I do to make my bone stronger as I have a very small frame.
I have had thyroid disease for years, and Severe lung disease.
I never smoked and certainly don't drink much only on occasions.
I don't like alcahol. Please advise if there is another way to strengthen bones.

Dawn

April 12. 2010 21:12

Hi Dr. Brown,

After 9 years on fosamax and two years on Boniva I decided to stop taking them 18 months ago
and added more D and calcium to my daily intake.  Last year my D count was 48 ng/mL and this year
it was 58ng/mL.  When I had my DEXA SCAN last month it was 10% worse for my spin and 9% worse in my hip then my test done two years ago. Spine T-Score -2.2 and Femoral Neck T-Score -1.7.  
Because of remodeling being done at my hospital where I have always gotten the scans done, I was sent to another sight for the test.  Could the use of a different scan make such a big difference in my T_Score this year?  Thank you and I love all your wonderful information!

Barbara Johanson

April 27. 2010 23:12

Hi Dr Brown,
I'm 41 and had an ultrasound scan of my bone density recently. The result was 'moderate to high-risk' of developing osteoporosis. Amongst the advice I received was to not drink coffee with meals. Is coffee in between meals OK then?  Also I take sumatriptan rather too often (to stop migraines). Does this drug deplete bone mass? Also I was wondering if chlorine in the water is bad for bones.
Yours sincerely,
Meg

Meg

May 5. 2010 21:01

Dear Dawn,
To begin with your low bone density is related to your weight.  As I have said before, thin people have small bones and get low bone density readings--the way the density testing machines work, you are going to have much less dense bone readings that a 175 lb woman.
I wonder if you have broken any bones?  Remember, the only real proof of true osteoporosis is the failure of bone to withstand normal loads. Beyond all this, it also seems that your bone issues are related to you other health problems, like thyroid and lung disease.  Working on these problems in as many natural ways as possible should help bone. Use of the Alkaline for Life Diet and the 20 key bone nutrients should help.  Tai Chi and Qi Gong breathing exercise would be great also.  In the Better Bones approach we like to work on the root causes of the bone issues, bit by bit.  Also try to keep you weight up as that too reflects on bone.

Susan Brown

May 5. 2010 21:05

Barbara,
Yes, different machines can make a big difference in bone density readings and it is good to use the same machine, if possible.  Nonetheless, people often lose bone upon withdrawal from the osteoporosis drugs and that would be what is happening.  A 10% change in 2 years is quite allot, so there might be some other hidden causes of this bone loss. It would be wise to ask your doctor for the tests I list in the Better Bones Medical Osteoporosis work-up. For details of these tests see http://www.betterbones.com/bonehealth/medicaltestingforosteoporosis.aspx.  Best wishes, Susan

Susan Brown

June 30. 2010 15:00

I heard that there were no commercial DEXA tests until Big Pharma started to develop bisphosphonates. It would make sense that diagnostics would go hand in hand in with treatment development; however, is it true that Hologic and Lunar scanners were developed and installed through joint financing of Big Pharma?

kirstin rogers

June 30. 2010 15:32

Dr. Brown,
   I was diagnosed with osteoporosis, December 2009.  I requested the DEXA scan out of curiosity, had no problems at all.  The results changed my life; femoral neck -3.7, hip -3.1.  I am trying not to panic and live a normal life.  I have drastically changed my lifestyle; healthy meals and daily exercise, and vitamin supplements.  As to your suggestion, I have had several tests run and the only problem so far is low vitamin D.  Of course, my medical doctor and gyn are strongly encouraging drugs; Fosamax and even Forteo.  I have had no breaks, fractures, no pain, etc.  I take no other medications and no history of prior medical issues.   I am caucasian, small frame, weight 115 pounds and otherwise very healthy.  I am trying to look at the positive side of this issue,  which has led me to be much more health conscious.  I don't want to live in a bubble because of one test score.  My doctor says I will definitely break a bone.  Do you think I should be more concerned and think about taking the drugs?

Brenda

June 30. 2010 21:58

Hello Brenda
last year in May i broke the upper femur bone in my right leg.
the endocrinologist said i'd need to take drugs or i would end up fracturing bones throughout my body and not know.

since then i have taken no drugs as i read a lot about them and how they were developed etc.

i have been doing Feldenkrais, increased my body's flexibility, lengthened my spine, muscles are now doing less work as the main thrust is carried by the skeleton and feel great.  i walk and now have begun to jog a little as well.  i sit correctly on my sit bones for the first time in about 15 years and have more energy and strength as a result of all this.  my food intake is much the same as i'm largely a vegetarian and low dairy eater.  AND i have not broken any more bones.  sometimes i feel doctors are influenced by the drug companies too much, and do not take the wholistic approach that is required.

my main observation was that before the break i was particularly sedentary, and also lacked a clear goal because my posture was poor and energy poor.  now i have loads of energy, great posture, and am studying Feldenkrais.  everything has improved for the better and i understand that it's more the cartilage connections that create the broken bones not bone density.  with flexibility and being able to connect bone throughout my whole body in the correct way has increased my chances of building stronger bone.  i am petite in frame and weight so my bone density is going to be petite as well.

hope this helps.
Stephanie

stephanie stone

July 1. 2010 16:09

Kristin, I find your questions interesting but I personally have not studied the political economics of bone density machine development. - Susan  

Susan Brown

July 1. 2010 16:18

Dear Brenda,

Please remember that your score is your status RELATIVE to the bone density of a standard, and you've already said that you're small-boned; that in and of itself is significant, as you'll have started out below the standard level on that basis alone. One DEXA is not enough to show whether you're LOSING bone, which would be the reason for concern. So do not panic, but instead, take this as an opportunity to find out what's happening with your bones' health.

The US Surgeon General advises diet and exercise before using medications for osteoporosis, and we agree with this advice - it's definitely not in keeping with the Surgeon General's recommendations to go onto a bone drug on the basis of one DEXA, when you haven’t fractured any bones and don't even know whether you're losing bone or why you lost bone in the first place. With all due respect to your doctor, having osteoporosis does not automatically mean you're going to fracture - bone density is only ONE factor in fracture risk. If you are really worried about your fracture risk, try taking our fracture risk assessment here http://www.betterbones.com/bonehealthprofile/default.aspx to get a better picture of where you stand.

Also remember that the Surgeon General also recommends testing for a full range of secondary causes--medical situations which might contribute to bone loss.  You might ask you doctor for any of the osteoporosis medical work-up tests that you have not yet been given.  For details on these tests see my article http://www.betterbones.com/bonehealth/medicaltestingforosteoporosis.aspx.

As far as what else you can do, here are some suggestions. At this point, you have uncovered one important health issue (the low vitamin D) and you've made some of the dietary changes we recommend. A couple of other things to look at: first, what is your pH? Your acid-base balance might be an important factor related to your bone health, so read more about it here: http://www.betterbones.com/alkalinebalance/default.aspx. Second, you might ask your doctor for an NTx test, which would give an indication of whether you're currently losing bone (learn more here: http://www.betterbones.com/bonehealth/bonebreakdowntests.aspx). Third, read up on the 20 key nutrients for bone health here http://www.betterbones.com/bonenutrition/20keybonenutrients.aspx and assess your diet to make sure that you're getting all of what you need. Fourth, you don't mention exercise - if you don't currently have a regular exercise program, it may benefit you to develop a low-impact exercise routine that emphasizes weight bearing exercise (our website store has a number of helpful videos that you can use as suggestions for what to do). Finally, try not to worry too much. Stress has an impact on bone health too, and since you've taken many positive steps already, I would encourage you to continue in this direction and find a method of promoting relaxation and calm in your life as a way of further supporting your bone health. You'll be amazed at what a positive mindset can do.

Best wishes for good health!

Susan Brown

July 1. 2010 19:56

Hi Susan,

How can I purchase the 20 essential bone-building nutrients?

Thanks for your information, which is very informative.  My dexa scan showed opteoporosis, Hip 3.2 and spine 3.0. N. P. said it was the worst result she has every seen and wanted me on Foxamax.  I said no. Increased my calcium to 1500 and 1000 Vit. D   Next year's dexa scan showed hip 3.1 and spine 2.9.  NP said that didn't mean anything and to take the Fosamax.  I also had fallen straight down on the floor couple years prior to the scan and it didn't hurt me at all.  After the dexa scan I tripped chasing my dog and fell on my knee and then landed on my hip on the concrete.  It didn't hurt me at all.  I am at average weight, but do have small bones.  I have increased my vitamin D to 2000 units a day.  My vitamin D results were 35 and want it to be at 50.  I feel that my osteoporosis was basically caused from my hyper thyroid that I had corrected 5 yrs prior.  My endocronologist said I had this thyroid problem for at least 10 to 15 yrs.

I feel that the essential bone building nutrients would assist me farther in getting my bones in better shape.
Thanks,

Linda

Linda P

July 1. 2010 23:24

Dear Susan,
    Thank you for taking the time to respond to my email.  You have given me the encouragement that I need.  I will follow your suggestions and check my pH and ask my doctor about the NTx test.  Yes, I am exercising daily.  I walk 4 miles each day/6 days a week and follow an exercise program with resistance type machines.  I visit your website often.  Thank you for the wealth of information.

Brenda

Brenda

July 2. 2010 09:55

Dear Brenda, You're very welcome, glad to be of help. You might consider adding weights or a weight vest to your walking routine. We're going to do a post or an article on that subject soon, as we've been looking at ways to enhance an exercise program to maximize bone-building. Best of luck!

Susan Brown

July 2. 2010 10:29

Dear Linda,

If I can respond on Susan's behalf - first, you're right that excess thyroid hormones can damage bone, and it may take some time for your bones to rebuild after years of coping with this underlying health issue. But if you fell more than once and had no injury, particularly if you fell hard, that's a very good sign that your bones are resilient, even if they're thin - thin bone doesn't have to be weak bone.

Most of the 20 key nutrients are readily available in a health food store, although I recommend you take the time to make sure the manufacturer follows the NSF Good Manufacturing Processes standards (otherwise you don't know that you're getting what the label says you're getting). Alternatively, you can sign up for the Program for Better Bones, which Susan developed with Women to Women. The Program includes supplements that provide these nutrients in the forms and amounts Susan considers most useful to the majority of women (and they are NSF-GMP certified). You can learn more about by looking under the "How Can We Help?" tab above. Fair warning that the Program includes more than just the supplements and is probably somewhat more expensive than buying off the shelf in a health food store, but the flip side is that it comes with a guide to making comprehensive bone health changes and customer support that helps you personalize the program so it's more appropriate to your specific needs. You can do it either way--whatever suits you best.

As far as your vitamin D is concerned, there are a number of reasons why the amounts you're using might not be bringing your level up. If you were seriously deficient before you started supplementing, perhaps the original amount just wasn't enough to compensate for that deficiency. Some people just don't absorb vitamin D well due to age, genetics, or skin type. If the increased level you're taking doesn't make a difference in your vitamin D level by autumn (assuming you don't already live in the sunny south!) you may want to investigate why that's the case. (Also be aware that low vitamin D can affect muscle strength and balance, and maybe that influenced the two occasions you fell - something to think about!)

Best of luck to you!

Managing Editor

July 4. 2010 10:38

I have started some exercises to strengthen core musles (in prone position). The PT tried having me use 1-lb weights while doing exercies for upper body - killed my elbows. I have chronic bilaterial tendonitis in both elbows plus tenosynovities in left wrist.
Back: severe arthritis, oseoporosis (-3-1); compression fracture at T12, and scoliosis. Have arthritis in hips and knees (Just had Bakers Cyst rupture) To add insult to injury, I have bad feet and can only sit or walk a short time. I work in my yard/garden and plan to get a treadmill for winter weather.  I do my own housework, etc.just can't get down to the floor well. Will be 77 in December.

Also am hypothroid; found out late last year, I was on too much medication for that and became hyperthroid. Hopefully now on right dose; also taking 50,000IU of Vit D once a month;started in March 2010.

So, any exercise suggestions for me?
Thanks.

Maureen

July 4. 2010 14:15

Since I think Dr. Brown is a genius, I thought I'd add a point or two:

1.  The 'gold standard' for bone strength is bone geometry (aka peripheral quantitative computerized tomography  (pQCT)).  Problem will be finding a machine.  Medicine & Science in Sports & Exercise:
November 2008 - Volume 40 - Issue 11 - pp S645-S653 doi: 10.1249/MSS.0b013e3181893cb7
November Supplement, Sex Differences in Parameters of Bone Strength in New Recruits: Beyond Bone Density, EVANS, RACHEL K et al.

2.  Vitamin X.  Any exercise is better than no exercise (except swimming & cycling) re bone strength, but impact exercise is the best.  Brisk walking, running, basketball, tennis, etc.  Weight training is good, but not as good.  Ideally, both.

3.  The calcium bioavailability research is muddy, but most bioavailable calcium is calcium citrate or maalate.  Your body can only absorb a max of 500 mg at one sitting, so divide your dose, with one dose at bedtime (sleep is your healing period).  Generally, calcium to magnesium ratio would be 2:1.

4.  Bones are living tissue and need a wide variety of nutrients to be strong (not just calcium which by itself is quite soft).  B, K, magnesium, boron, omega 3s, etc.  So, the ideal is to get a comprehensive blood chemistry to look at all variables.  You can buy these on line or get as part of your physical.

5.  A mildly alkaline serum level is important for max uptake.  See Dr. Brown's recommendations.

6.  The nutritional DRI are gender and age specific, but tend to be broad population averages.  

Since vitamin D production varies widely by age, bodyfat, latitude, season, genes, skin color, etc., it is IMHO useless to discuss daily IU doses without a 25(OH) D test (goal is 50-80 ng/ml)).  Studies with pregnant women used 4,000 to 6,400 IU/day, for example.  Ideal is test-dose-retest-repeat.  Low scores might need 50,000 IU D3/day for 8 days to bring serum levels up to normal, then drop back to a maintenance dose.  D also affects muscle structure, balance, urinary incontinence, etc. as well as pregnancy issues, diabetes, immune system, cardio-vascular disease, some cancers, etc.

Same for calcium... if you were a serious athlete who trains hard and sweats a lot, you might need 2,000 mg calcium a day.

7.  Obviously don't smoke or overindulge in flavored cleaning solvent (aka alcohol).

Jim Larsen

July 6. 2010 09:51

I had my first DEXA at age 52, when I was premenopausal.  It showed osteopenia in hip and L spine.  Without further testing, oral bisphosphonates were suggested--which I rejected.  Three years later another DEXA showed worsening bone density with osteoporosis in L spine.  Again, oral meds were strongly suggested without any further testing, including vit. D level--again I rejected.  The osteoporosis coupled with elevated blood calcium level (10.8)in Feb. 2007 led to a diagnosis of hyperparathyroidism--which affects bone density.  Parathyroid surgery in Jan. 2008 was unsuccessful at curing hyperparathyroidism.  After surgery, endocrinologist recommended vit. D and calcium and ordered DEXA with scan of left forearm in addition to customary L spine and hip.  Left wrist was
-4.4.  Calcium and PTH levels were followed for a year with numbers fluctuating in and out of normal range.  Finally, I had surgery again last month with removal of a parathyroid gland and part of my thymus gland, as the parathyroid gland was imbedded in my thymus gland.  Calcium and PTH levels dropped beautifully during surgery.  Now it is watch and wait to see if I will remain stable.  My DEXA just prior to surgery showed worsening of osteoporosis in left wrist and overall in L spine.  Left hip density improved by 0.1.  I have my scans done in my gyn's office.  He called me in for an appointment to discuss treatment.  Because I have a history of acid reflux, he is suggesting Reclast IV.  Discussion regarding side effects focused mainly on mild flulike symptoms.  I have been researching Reclast and am horrified by the number of healthy people who have had prolonged terrible muscular and bone discomfort after taking this medication.  Also, I was very much concerned when I read the product leaflet on the web site of the parent company.  There is a section that states that Reclast might not be for some people, and everyone is urged to tell the treating physician of any history of thyroid/parathyroid problems or surgery.  My gyn never talked about this connection, and he is aware of my medical history, as I have been refusing osteoporosis treatment until my parathyroid problem was corrected.  I generally walk 3 mi. a day in addition to going to a gym to use weight machines 2-3 times a week.  I am taking approximately 1200 mg a day of calcium through supplementation and diet.  I take 4000 IU of vitamin D daily.  I drink 8-10 glasses of water a day and am trying to eat a mostly alkaline diet.  I am very reluctant to agree to Reclast IV because of both the terrible ongoing side effects people have reported and my history of parathyroid disease.  My surgeon has indicated that it will be important to monitor my calcium and PTH levels for about a year to determine whether this most recent surgery has completely corrected the hyperparathyroidism.  Does anyone have any experience with treating osteoporosis that has been complicated by a similar condition? Thank you for any information that might be offered

Janell

July 6. 2010 13:12

Maureen, We'll be posting a new article about exercise fairly soon, so keep an eye out for it.

Janell, Please see Dr. Brown's post about parathyroid, vitamin D, and magnesium deficiency -- there's some information in it that you may find useful. www.betterbones.com/blog/post/vitamin-d-parathyroid-hormone-levels-magnesium-deficiency.aspx

Managing Editor

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