A 78 year old Chinese lady came to see you with back pain. A plain lumbar spine x-ray showed lumbar spondylosis in L3, L4 and L5. There were no obvious vertebral fracture but the bones were reported as “osteopenic”. She had well-controlled hypertension on valsartan but was otherwise well with no history of fracture. You did a DXA for her and found her results showed osteoporosis. She was started on weekly alendronate with vitamin D3. After 5 years of treatment, she had another DXA. These are her results:
Which of the following statements are CORRECT, when comparing the 2 DXA results?
The correct answer is 1 & 3:
1. There has been no significant increase in her total hip BMD
3. There has been an 8.5% increase in her lumbar spine BMD suggestive of an adequate response to treatment.
When assessing whether there has been a significant change in BMD on treatment, remember the concept of “least significant change”, to determine if there has been a true interval change in BMD. For the spine, there has to be a change of at least 3-4%, 4-6% at the femoral neck and 2-3% at the wrist. Thus for statement 1, for total hip BMD, there was an increase of +2%, which is not a significant increase, thus TRUE. Similarly, for statement 3, an increase of +8.5% in lumbar spine BMD is an adequate response – TRUE. For statement 4, an increase of +4.6% in the femoral neck is adequate, thus it is FALSE. For statement 2, the least significant change is calculated on BMD, not T-scores, thus FALSE. For statement 5, we would expect that after 5 years, there would have been enough time to determine if the drug is working, thus FALSE. At the minimum, we would expect to see a response by 2 years.
By Dr Swan Sim Yeap, Consultant Rheumatologist, Subang Jaya Medical Centre, Selangor, Malaysia
A 70 year old lady with rheumatoid arthritis (RA) on low dose Prednisolone 5 mg od, mentions in a routine follow-up in July 2021 that her elder sister aged 74 years had fractured her R hip after a fall in the bathroom in May 2021. You do her DXA and the results are as follows:
The lumbar spine BMD was not measured as she had a previous operation on L2 for removal of a benign schwannoma in April 2021.
L FN BMD 0.561, T-score -2.3, Z-score -0.2
L TH BMD 0.630, T-score -1.9, Z-score -0.6
L 1/3 wrist BMD 0.624, T-score -1.0, Z-score 1.1
The correct answer is She needs further assessment of her fracture risk using a risk calculator such as FRAX.
This lady has several significant risk factors for osteoporosis, namely her advanced age, RA and on corticosteroids. A family history of osteoporotic fracture in a first degree relative is also a risk factor, but not as strong as if she has a fracture herself. So thus, from the history, there is no indication to start treatment immediately (statement A). However, the correct answer is D, in that she needs further assessment of her fracture risk. Thus, statements B and E are also not correct as she need further fracture risk assessment. Statement C is also not correct as calcium and vitamin D are important adjuncts when taking osteoporosis treatments, but not enough as treatments on its own.
When her FRAX score was calculated, her 10 year fracture risk for major osteoporotic fracture was 28% and for hip fracture 12%. In patients with osteopenia, many osteoporosis guidelines suggest that treatment should be started at a 10 year fracture risk of major osteoporosis fracture of 20% and hip fracture of 3%, following the USA guidelines. (Camacho PM et al. American Association of Clinical Endocrinologists/American College of Endocrinology Clinical Practice Guidelines for the Diagnosis and Treatment of Postmenopausal Osteoporosis. Endocr Pract. 2020; 26 (Suppl 1): 1-44). Thus she would be a candidate for drug treatment.
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