Standards and guidelines for performing central dual X-ray densitometry from the Canadian Panel of International Society for Clinical Densitometry

Fibroblast Growth Factor-23, Sclerostin, and Bone Microarchitecture in Patients With Osteoporotic Fractures of the Proximal Femur: A Cross-sectional Study

This cross-sectional observational cohort study was designed to simultaneously investigate bone microarchitecture and serum markers of bone metabolism in elderly osteoporotic patients experiencing a trochanteric or femoral neck fracture. Special emphasis was put on renal function, sclerostin and fibroblast growth factor-23 (FGF-23). Eighty-two patients (median age: 84 years; 49 trochanteric fractures) scheduled for emergency surgery due to an osteoporotic fracture participated. Bone specimens for ex vivo microcomputed X-ray tomography were sampled during surgery. Blood samples for laboratory workup were collected before surgery (t0) and 1 day afterward (t1). Fifty-eight patients consented to dual-energy X-ray absorptiometry scanning of the lumbar spine and/or contralateral femoral neck after recovery during the in-patient stay. Samples were grouped according to the site of fracture. Regression coefficients were controlled for age and/or estimated glomerular filtration rate (eGFR), if appropriate. Patients experiencing a femoral neck fracture presented with better preserved renal function (eGFR) and lower C-terminal fragment of fibroblast growth factor-23 (cFGF-23) concentrations compared to those with trochanteric fractures. By contrast, serum sclerostin was similar at both time points and did not differ between groups. Age-adjusted correlation analysis revealed negative associations between eGFR and cFGF-23 determined at t1 (R=-0.34; p<0.05) as well as between eGFR and sclerostin levels at t0 (R=-0.45; p<0.05) in patients with trochanteric and femoral neck fractures, respectively. Our study provides evidence that not only an age-related decline of renal function but also the type of skeletal injury may contribute to the circulating concentrations of cFGF-23.

Creatinine and myoglobin are poor predictors of anaerobic threshold in colorectal cancer and health

AIMS

Myoglobin is a haem protein produced in skeletal muscles. Serum concentrations of myoglobin have been proposed as a surrogate marker of muscle mass and function in both cachectic cancer patients and healthy non-cancer individuals. Creatinine, a metabolite of creatine phosphate, an energy store found in skeletal muscle, is produced at a constant rate from skeletal muscle. Urinary and plasma creatinine have been used in clinical practice as indicators of skeletal muscle mass in health and disease. Our study aimed to test the hypothesis that plasma myoglobin and creatinine concentration could accurately predict skeletal muscle mass and aerobic capacity in colorectal cancer (CRC) patients and matched healthy controls and thereby an indicative of aerobic performance.

METHODS

We recruited 47 patients with CRC and matching number of healthy volunteers for this study. All participants had their body composition measured by dual-energy X-ray absorptiometry scan, aerobic capacity measured to anaerobic threshold (AT) by cardiopulmonary exercise testing and filled in objective questionnaires to assess the qualitative functions. This study was carried out in accordance with the Declaration of Helsinki, after approval by the local National Health Service (NHS) Research Ethics Committee.

RESULTS

Age-matched groups had similar serum myoglobin and creatinine concentrations in spite of differences in their aerobic capacity. AT was significantly lower in the CRC group compared with matched controls (1.18 ± 0.44 vs. 1.41 ± 0.71 L/min; P < 0.01). AT had significant correlation with lean muscle mass (LMM) among these groups, but myoglobin and creatinine had poor correlation with LMM and AT.

CONCLUSIONS

Serum myoglobin is a poor predictor of muscle mass, and serum myoglobin and creatinine concentrations do not predict aerobic performance in CRC patients or healthy matched controls.

Changes in bone mineral density in men starting androgen deprivation therapy and the protective role of vitamin D

SUMMARY

Androgen deprivation therapy in 80 men was associated with declines in bone mineral density (BMD), which were greatest in the first year, and in the lumbar spine compared to controls. Vitamin D use was associated with improved BMD in the lumbar spine and in the first year.

INTRODUCTION

Decreased BMD is a common side effect of androgen deprivation therapy (ADT), leading to increased risk of fractures. Although loss of BMD appears to be greatest within the first year of starting ADT, there are few long-term studies of change in BMD, and risk factors for bone loss are not well-characterized.

METHODS

Men aged 50+ with nonmetastatic prostate cancer starting continuous ADT were enrolled in a prospective longitudinal study. BMD was determined by dual-energy x-ray absorptiometry at baseline and yearly for 3 years. Matched controls were men with prostate cancer not receiving ADT. Multivariable regression analysis examined predictors of BMD loss.

RESULTS

Eighty ADT users and 80 controls were enrolled (mean age 69 years); 52.5 % had osteopenia and 8.1 % had osteoporosis at baseline. After 1 year, in adjusted models, ADT was associated with significant losses in lumbar spine BMD compared to controls (-2.57 %, p = 0.006), with a trend towards greater declines at the total hip (p = 0.09). BMD changes in years 2 and 3 were much smaller and not statistically different from controls. Use of vitamin D but not calcium was associated with improved BMD in the lumbar spine in year 1 (+6.19 %, p < 0.001) with smaller nonsignificant increases at other sites (+0.86 % femoral neck, +0.86 % total hip, p > 0.10) primarily in the first year.

CONCLUSIONS

Loss of BMD associated with ADT is greatest at the lumbar spine and in the first year. Vitamin D but not calcium may be protective particularly in the first year of ADT use.

Predictors of bone mineral density in a convenience sample of young Caucasian adults living in southern Ontario

Osteoporosis is a major public health concern in Canada and worldwide. Although much is known about bone health in older adults, little is known about bone health in young, healthy Canadian men and women. The objectives of this research were to describe bone mineral density (BMD) of young, healthy adults living in southern Ontario, Canada, and to identify predictors of BMD in this population. Two-hundred and fifty-eight Caucasian men and women aged 18–33 years completed health and physical activity questionnaires along with a calcium and vitamin D specific food frequency questionnaire. Height and mass were measured. BMD of the total hip, femoral neck, spine, and total body was measured using dual energy X-ray absorptiometry. Among men, body mass, weight-bearing physical activity, and calcium intake were significant predictors of BMD. Among women, body mass, calcium intake, and family history of osteoporosis significantly predicted log BMD. The predictors of BMD in young Canadian men and women identified in this study may inform the development of longitudinal studies designed to examine the influence of lifestyle factors on BMD in young adults.

Some physical and clinical factors influencing the measurement of precision error, least significant change, and bone mineral density in dual-energy x-ray absorptiometry

Dual-energy X-ray absorptiometry (DXA) is the standard method of measuring bone mineral density (BMD) at highly trabecular bone, which can be statistically linked to the risk of fracture. For DXA, precision error (PE) and phantom-based accuracy studies are among the most important routine quality control procedures. A precision study was performed at our institution using International Society for Clinical Densitometry guidelines. Comparing our results with those reported by other investigators, we draw the following general conclusions: the PE was higher for the spine than the hip, which we attribute to the better geometric reproducibility at the hip. The hypothesis that the DXA calculates BMD relative to water was validated. Whether follow-up measurements are performed by the same technologist on the same day-or different technologists on subsequent days-does not appear to have a clinically significant impact on PE or least significant change (LSC). Mixing beam types (i.e., fan and pencil) may affect lumbar PE and LSC measurements more significantly than those of the hip. The use of a single technologist may reduce the PE for the lumbar spine but appears to increase it for the hip. Restricting the patient population to the female gender has the apparent effect of narrowing the gap between lumbar and hip PEs. Finally, the degree of BMD measurement accuracy can be affected by the type of phantom being used (e.g., European Spine Phantom vs Lunar phantom) and the faults in specific DXA edge detection algorithms.

Clinical utility of spine bone density in elderly women

It is common clinical practice to obtain a bone density measurement at both the hip and spine to evaluate osteoporosis. With aging, degenerative changes in the lumbar spine may elevate the bone mineral density (BMD) results giving false assurances that the fracture risk at the spine is low. We examined the association of spine osteoarthritis and bone mineral density in 1082 community-dwelling ambulatory older women aged 50-96 years who participated in a 1992-1996 osteoporosis research clinic visit. The BMD was measured at the hip and posteroanterior (PA) and lateral lumbar spine using dual energy X-ray absorptiometry (DXA). Spine osteoarthritis was identified on the PA lumbar spine DXA images by a musculoskeletal radiologist. Forty percent of women had evidence of spine osteoarthritis (OA). Women with spine OA had a mean age of 77.4 yr (95% confidence interval [CI]: 76.5-78.2), were significantly older than women without spine OA (mean age, 66.8 yr; 95% CI: 65.9-67.7), and were more likely to have prevalent radiographic fractures (14.2% vs. 9.5%; p<0.05). Age-adjusted BMD at the femoral neck, total hip, PA spine, and lateral spine was significantly higher in women with spine OA. Women with spine OA were more likely to have osteoporosis by the World Health Organization classification at the femoral neck and total hip than those without spine OA, but less likely based on the PA spine (14.4% vs. 24.5%). Despite higher BMD levels, women with OA of the lumbar spine had higher prevalence of osteoporosis at the hip and more radiographic vertebral fractures. In elderly women 65 yr and older who are likely to have spine OA, the DXA measurement of the spine may not be useful in assessing fracture risk, and DXA of the hip is recommended for identification of osteoporosis.

Standards for performing DXA in individuals with secondary causes of osteoporosis

This document addresses skeletal health assessment in individuals with secondary causes of osteoporosis. Recommendations are based on consensus of the Canadian Panel of the International Society for Clinical Densitometry and invited international experts. Bone mineral density (BMD) testing in these populations is performed in conjunction with careful evaluation of the disease state contributing to bone loss and increased fragility fracture risk, as well as assessment of other contributing risk factors for fracture. The presence of secondary causes of bone loss may further increase the risk of fracture independently of BMD and may necessitate earlier pharmacologic intervention. Dual-energy X-ray absorptiometry is indicated in the initial workup of secondary causes of osteoporosis. The BMD fracture risk relationship is not known for individuals with chronic renal failure (CRF). The BMD testing in this population may be normal in the presence of skeletal fragility, and quantitative bone histomorphometry is better at evaluating skeletal status than BMD in CRF. Dual-energy X-ray absorptiometry is a valuable tool in assessing skeletal health in individuals with secondary causes of osteoporosis.

Minimum sample size requirements for bone density precision assessment produce inconsistency in clinical monitoring

INTRODUCTION

Detection of change during bone mineral density (BMD) monitoring is affected by test precision. The International Society of Clinical Densitometry (ISCD) recommends that each center determine precision error using repeat measurements in 30 subjects (or an equivalent method providing 30 degrees of freedom).

METHODS

We hypothesized that this sample size may be too small for a robust precision estimate, which could affect the performance of BMD monitoring in clinical practice. Replicate measurements of the spine and total hip (198 spine and 193 hip scan pairs) were obtained (interval 6+/-5 days). The sample was randomly divided into six groups of 30 patients each. Root mean square standard deviation (RMS-SD in g/cm(2)) and coefficient of variation (RMS-CV in %) precision errors and corresponding 95% least significant change (LSC) were calculated for each group and the pooled sample. LSC cutoffs were applied to 1,420 individuals from the Manitoba Bone Density Program who had follow-up measurements on the same instrument (interval 21+/-9 months). While the pooled spine RMS-SD was 0.017 and pooled hip RMS-SD was 0.009 g/cm(2), sample sizes of 30 gave a range of RMS-SD point estimates from 0.012 to 0.021 for the spine and from 0.008 to 0.012 for the hip.

RESULTS

When the respective LSC cutoffs were applied to the 1,420 follow-up scan pairs, the fraction of patients categorized with significant change in the spine varied from 20.7% to 46.0%; four of the six LSCs based upon 30 subjects gave fractions significantly different from the pooled LSC of 30.7%. Significant change fractions for the hip varied from 31.1% to 51.1%; two of the six LSCs based upon 30 subjects gave fractions significantly different from the pooled LSC of 40.1%. Similar results were obtained using relative precision errors.

CONCLUSION

BMD precision studies using a sample size of 30 are insufficient to reliably characterize precision error or change during clinical monitoring.

Training requirements for DXA technologists in the United States

The purposes of this study were to determine, by state, the requirements for dual-energy X-ray absorptiometry(DXA) operators' training, knowledge of these state requirements, and factors that predicted state and International Society of Clinical Densitometry (ISCD) certification of DXA technologists. Seventeen states required registered technologist (RT) certification or authorized/licensed limited certification for DXA operators, 16 had no certification requirements, 12 required RT certification, and 5 had state-specific requirements. There were 9745 surveys mailed toDXA users including 50% Hologic Inc., 50% GE Lunar, and 100% Norland; 3148 surveys are included in this analysis. Among responders who indicated that their state did not have any certification requirements (n=1673), 1095(65.5%) were incorrect; there were requirements. Possession of state and ISCD certification was significantly correlated with the number of patients scanned per week (p<or=0.05), the number of technologists employed within a center (p<0.01), and the subspecialty of the practitioner (p<or=0.02). Our study uncovered a lack of uniformity amongstates with respect to central DXA operator training requirements. Additionally, in those states with requirements, DXA operators were often unaware of these requirements. Uniform national training requirements for central DXA operators to ensure adequate DXA scan quality are urgently needed.

Relationship among densitometry, bone histomorphometry, and histologic stage in idiopathic myelofibrosis

Idiopathic myelofibrosis (IMF) induces dramatic changes in bone. Bone remodeling and densitometric alterations in a series of nine patients with IMF and their relationship with the histologic stage of the disease were assessed. Patients were included at diagnosis and a bone marrow biopsy, dual-energy X-ray absorptiometry, and transiliac bone biopsy for histomorphometric analysis were performed. Five cases were classified as IMF histologic stage 1, one as stage 2, and three as stage 3. Compared with 40 age- and sex-matched controls, the following histomorphometric parameters were significantly higher in our patients: bone volume (BV/TV), osteoblast surface (Ob.S/BS), eroded surface (ES/BS), osteoclast surface (Oc.S/BS), osteoclast number (N.Oc/TA), mineralizing surface (MS/BS), reversal period (Rv.P), and remodeling period (Rm.P). Mineral apposition rate (MAR) and erosion depth (E.Depth) were significantly decreased (P < 0.05 for all comparisons). Bone mineral density (BMD) measurements showed high values for patient age and sex both at femur neck (Z score range +0.19 to +7) and total femur (Z score range -0.09 to +6.48). When densitometric values were analyzed according to IMF histologic stage, patients in stages 1 and 2 had significantly lower BMD values than to those in stage 3 (P = 0.024). In conclusion, patients with IMF present a characteristic bone histomorphometric pattern with increased bone volume and bone cells but low apposition and decreased erosion depth, suggesting a positive balance in bone remodeling units. This balance would produce the increase in bone mass observed in this disease. Given the increase in BMD observed with more advanced stages of IMF, this noninvasive method could be useful tool for assessing IMF progression.

Bone density monitoring with the total hip site: time for a re-evaluation?

Serial measurement of bone density is important in the clinical management of osteoporosis because it helps to confirm therapeutic response and identify individuals who continue to lose bone density. The lumbar spine is often stated to be the preferred site for monitoring purposes, but much of the supporting information derives from the relatively poor precision of the femoral neck, which is known to be less reproducible than the total hip. The Manitoba Bone Density Program delivers clinical services to the Province of Manitoba, Canada and maintains a detailed quality assurance program. We compared lumbar spine and total hip reproducibility using a pencil-beam scanner (n = 82), a fan-beam scanner (n = 92), and a cross-calibration between the two scanners (n = 61). Each comparison showed significantly lower measurement error at the total hip than at the lumbar spine (p < 0.001). We assessed the likelihood that follow-up measurements would show an absolute difference exceeding the least significant change in routine clinical practice (n = 2412 paired examinations). The total hip measurement detected change more frequently than the lumbar spine in each of these comparisons. In summary, we believe that the total hip site has been undervalued for monitoring purposes and might actually be the preferred site in older individuals with a high prevalence of lumbar spine artifact.