Rational Use of DXA-BMD a Case based approach - Gregory Kline MD FRCPC

Disclosures (since 2009) no relationships or conflicts to declare

Objectives discussion of what BMD does and does not add to “screening/diagnosis” in osteoporosis discuss indications for and limitations of serial BMD tests review the related 2016 TOP Osteoporosis guidelines in clinical context most important! Learn to think about what BMD might add BEFORE you order it.

Cases for discussion Case 1: when to do the “first” bone density Case 2: serial “screening” bone density Bonus material

Case 1: principles, not rules the “first” BMD

Mrs. B Mrs. B is a 50 year old healthy woman, no medications, no family history of hip fracture. Height 152.6 cm, weight 61 kg She is concerned about developing osteoporosis and requests a “baseline” BMD How do you respond and what reasons would you give either for or against?

Thinking it through What are we looking for with a “baseline” BMD? remember: bone loss is universal with age - don’t need a test to prove ageing. What will you do if it shows T score > -2.0? What will you do if it shows T score -2.3?

Thinking it through: if the baseline BMD is “good” A “baseline” measure implies that there will be a future measure which may be different than baseline AND The rate of change between baseline and repeat measure is of relevance to management. REALITY: the baseline BMD will simply reflect the time that has passed since menopause REALITY: 100% chance that the next BMD will be lower REALITY: management decisions will depend on the next BMD....no relevance to “baseline”

Thinking it through: what if the baseline BMD is “bad”? What are the chances that a BMD, done now, in the absence of other risk factors, will be so low that it actually warrants medical therapy to be started right now? Assume that medical therapy is warranted for a 10 year fracture risk of 20% or higher.... She would need to have a T-score of -4.5 The odds of that, in a healthy 50 year old < 1/10,000 And by the way, if she did have a T-score of -4.5 at age 50...she likely has some kind of metabolic bone disease…..

guidance

know the paradigm When we screen for osteoporosis: we should NOT be screening to “find” low BMD because many will not warrant treatment anyways what is the point of screening for something that is a natural process of ageing and affects 100% of people rather, appropriate osteoporosis screening should: be designed to find people who are at such high fracture risk that drug intervention is warranted.

Practical meaning

how to think in practice the idea is to “find” people who have at least 20% chance of fracture in the next 10 years BMD is a tool that may help find some of those people

examples

exhibits A) a 60 year old woman with polymyalgia rheumatica on prednisone 10 mg daily x 9 months. Smoker, height 168 cm weight 62 kg. B) a 70 year old woman with mild kyphosis and maternal history of hip fracture. Height 165 cm, weight 59 kg. C) a 59 year old female smoker with family history of hip fracture. Height 165 cm, weight 73 kg. D) 62 year old healthy woman with no risk factors, height 166 cm, weight 75 kg.

exhibits A) a 60 year old woman with polymyalgia rheumatica on prednisone 10 mg daily x 9 months, previous wrist fracture. Smoker, height 168 cm weight 62 kg. 10 year major OP # risk: 23% (FRAX score, no BMD) B) a 70 year old woman with mild kyphosis and maternal history of hip fracture. Height 165 cm, weight 59 kg. 10 year major OP # risk: 31% (FRAX score, no BMD) C) a 59 year old female smoker with family history of hip fracture. Height 165 cm, weight 73 kg. 10 year major OP # risk: 11.5% (FRAX score, no BMD) D) 62 year old healthy woman with no risk factors, height 166 cm, weight 75 kg. 10 year major OP # risk: 7% (FRAX score, no BMD)

exhibits A) a 60 year old woman with polymyalgia rheumatica on prednisone 10 mg daily x 9 months, previous wrist fracture. Smoker, height 168 cm weight 62 kg. 10 year major OP # risk: 23% (no BMD) OP # risk with T-score -2.6: 26% OP # risk with T-score - 1.5: 18% B) a 70 year old woman with mild kyphosis and maternal history of hip fracture. Height 165 cm, weight 59 kg. 10 year major OP # risk: 31% (no BMD) OP risk with T-score -2.6: 31% OP # risk with T-score -1.5: 20% C) a 59 year old female smoker with family history of hip fracture. Height 165 cm, weight 73 kg. 10 year major OP # risk: 11.5% (no BMD) OP risk with T-score -2.6: 19% OP risk with T-score -1.5: 12.5% D) 62 year old healthy woman with no risk factors, height 166 cm, weight 75 kg. 10 year major OP # risk: 7% (no BMD) OP # risk with T-score - 2.6: 11% OP # risk with T-score -1.5: 7%

exhibits BMD changes nothing! BMD changes nothing! A) a 60 year old woman with polymyalgia rheumatica on prednisone 10 mg daily x 9 months, previous wrist fracture. Smoker, height 168 cm weight 62 kg. 10 year major OP # risk: 23% (no BMD) OP # risk with T-score -2.6: 26% OP # risk with T-score - 1.5: 18% B) a 70 year old woman with mild kyphosis and maternal history of hip fracture. Height 165 cm, weight 59 kg. 10 year major OP # risk: 31% (no BMD) OP risk with T-score -2.6: 31% OP # risk with T-score -1.5: 20% C) a 59 year old female smoker with family history of hip fracture. Height 165 cm, weight 73 kg. 10 year major OP # risk: 11.5% (no BMD) OP risk with T-score -2.6: 19% OP risk with T-score -1.5: 12.5% D) 62 year old healthy woman with no risk factors, height 166 cm, weight 75 kg. 10 year major OP # risk: 7% (no BMD) OP # risk with T-score - 2.6: 11% OP # risk with T-score -1.5: 7% BMD changes nothing! BMD changes nothing! *BMD will be useful* BMD changes nothing!

Guidelines in context

TOP guidelines Feb 2016 suggest screening BMD for women age > 65 because advanced age is a major risk factor suggest screening BMD for men or women >50 with risk factors (long list) memorize the list OR use FRAX score without BMD www.topalbertadoctors.org/download/1907/Osteoporosis%20CPG.pdf

Case-based messages Case 1: the first bone density “baseline” bone density concept is of no medical use and should be discouraged bone density is an occasionally useful tool for fracture risk estimation in patients who are not obviously at very high (>20%) or very low (<10%) risk. goal is to find people at high fracture risk goal is not to find people with low BMD

Case 2 - serial “screening” Mrs. C is 66 years old. She has no fracture risk factors. She had a screening BMD done last year, showing femoral neck T-score -1.7. No specific therapy was started. She asks if she should have a repeat BMD this year to see if it has changed. Will it have changed? What is the chance she will have crossed a treatment threshold on the basis of bone loss in the past year?

guidance

interpretation They lack other risk factors OR If a BMD is done (“rightly” or “wrongly”) and the patient is far away from an interventional threshold either because They lack other risk factors OR Their current risk factors + BMD still puts them at low risk It will take somewhere between 2 and 15 years for even 10% of such persons to see enough BMD loss to actually cross an interventional threshold (all other risks being equal)

PRActical meaning

practical meaning The value to annual or biannual BMD testing (all other risks being constant) is virtually zero since overall fracture risks (and therefore, distance to treatment threshold) changes minimally in less than 3-5 years.

examples

long term monitoring? 66 year old woman, height 170 cm, wt 73 kg, no risks, screening BMD T-score -1.7 OP # risk 8.6% 67 years old, BMD T-score -1.9 OP # risk 9.5% 68 years old, BMD T-score -1.9 OP # risk 9.8% 69 years old, BMD T-score -2.2 OP # risk 11.4% 70 years old, BMD T-score -2.3 OP # risk 12.1% 71 years old, BMD T-score -2.6 OP # risk 14.3%

how much did it add? NOT VALUABLE NOT VALUABLE NOT VALUABLE 66 year old woman, height 170 cm, wt 73 kg, no risks, screening BMD T-score -1.7 OP # risk 8.6% 67 years old, BMD T-score -1.9 OP # risk 9.5% 68 years old, BMD T-score -1.9 OP # risk 9.8% 69 years old, BMD T-score -2.2 OP # risk 11.4% 70 years old, BMD T-score -2.3 OP # risk 12.1% 71 years old, BMD T-score -2.6 OP # risk 14.3% NOT VALUABLE NOT VALUABLE NOT VALUABLE NOT VALUABLE NOT VALUABLE?

maternal hip # reported Thinking about what you might find first… 65 year old woman, height 170 cm, wt 73 kg, no risks, screening BMD T-score -1.7 OP # risk 8.6% Age other risks risk (no BMD) risk (T-2.0) risk (T-3.3) 66 8.6% 9.6% 17.5%* highly unlikely! 67 maternal hip # reported 15.1% 17.2%* most likely but adds little 29%* useful if the first BMD 68 15.3% 17.2% 29.8% 69 15.5% 17.1% 30.8%

how much does BMD add…? if a prior BMD exists from the past 3-5 years, a repeat measure rarely adds to your updated FRAX assessment (use the old BMD result!) if over age 50 and a new major risk factor acquired, consider new BMD if: no prior BMD within 5 years AND intervention not already obviously indicated by risk factors alone General principle: before ordering BMD, consider whether it is likely to really change anything; FRAX calculation may help.

guidelines in context

TOP guidelines 2016 repeated BMD testing alone provides little value to decision-making in osteoporosis www.topalbertadoctors.org/download/1907/Osteoporosis%20CPG.pdf

Case-based messages (2) Case 2: serial “screening” bone density intervals for repeat screening depend upon fracture risk at last screening visit, not necessarily time-standardized. fracture risk and BMD change very slowly annual BMD almost never useful unless patient has also acquired new major risk factors as well since goal is to find people who are at intervention threshold, serial screening need not necessarily be BMD- driven

bonus material

BMD measures “on therapy” BMD “change” in either direction not really predictive of anything while on therapy BMD / scoring systems on therapy not useful for fracture risk estimation BMD - driven changes to therapy (medication switching) not supported by evidence Undetermined role of BMD monitoring around bisphosphonate “holiday”

Monitoring Osteoporosis Therapy With Bone Densitometry Misleading Changes and Regression to the Mean JAMA. 2000;283(10):1318-1321. doi:10.1001/jama.283.10.1318.

examples patient on alendronate, follow up BMD shows 2% decrease. Action: nothing. patient on alendronate, follow up BMD shows 3% decrease. Action: probably obligated to repeat next year…..BMD no change….action: nothing. patient on alendronate, follow up BMD shows no change. Action: nothing. patient on alendronate, follow up BMD shows 10% decrease. Action:investigate……but very rare situation! Controversy: is serial BMD broadly warranted to find very rare cases of occult metabolic bone disease / cancer?

exhibits (2) patient on bisphosphonate has repeat BMD (no change), report says “high risk of fracture” is this true? is this a surprise? does this change anything?

when does repeat BMD on therapy help? little evidence to answer this question possibly if suspected malabsorption of oral bisphosphonate possibly during bisphosphonate holiday and therefore, possibly at the “end” of bisphosphonate treatment, prior to bisphosphonate holiday

summary

BMD uses baseline BMD at menopause - discourage choice to do BMD should FOLLOW, not precede, a review of risk factors BMD is most useful in cases of indeterminate risk …which usually means people with fracture risk factors or advanced age without risk factors serial BMD in untreated patients should likely be 3 - 5 years apart in order to be useful serial BMD in treated patients is of very low value in most cases