Dual-energy X-ray Absorptiometry Quality Matters

Impact of osteosarcopenia on disability and mortality among Japanese older adults

BACKGROUND

In clinical settings, muscle mass and bone mineral density assessments are usually performed using dual-energy X-ray absorptiometry (DXA), the clinical standard technique. However, DXA is often unavailable in community settings. This study aimed to determine whether osteoporosis, osteopenia (OP) and sarcopenia (SP) identified by simplified instruments are associated with the future incidence of disability and mortality and evaluate the validity of these instruments as community screening tools. We also examined osteosarcopenia (OS), defined as the coexistence of OP and SP, as a new indicator of geriatric syndromes to determine whether it has an additive effect on adverse outcome incidence compared with OP and SP alone.

METHODS

In total, 8995 older adults participated in the study (women: 51.7%, average age: 73.5 ± 5.4 years). Data were extracted from the Japanese national cohort study, National Center for Geriatrics and Gerontology-Study of Geriatric Syndromes. We determined OP based on T-scores generated based on the speed of sound, which is the time taken for ultrasound waves to go through a determined distance in the calcaneus bone. Skeletal muscle mass was evaluated using a bioimpedance analysis device. Handgrip strength and walking speed were measured as physical performance indicators. Incidences of disability and mortality were prospectively determined for 5 years.

RESULTS

The prevalence of OP, SP and OS was 45.5%, 3.9% and 7.4%, respectively. The incidence of disability in the nonOP/nonSP, OP, SP and OS groups was 6.5%, 14.9%, 20.5% and 33.5%, respectively. The incidence of mortality in the nonOP/nonSP, OP, SP and OS groups was 4.0%, 4.9%, 10.3% and 10.2%, respectively. Participants with OP (hazard ratio [HR]: 1.45, 95% confidence interval [CI]: 1.25-1.68), SP (HR: 1.38, 95% CI: 1.08-1.76) and OS (HR: 1.73, 95% CI: 1.43-2.09) had a higher risk of disability than nonOP/nonSP participants. Participants with OP (HR: 1.31, 95% CI: 1.04-1.64) and OS (HR: 1.45, 95% CI: 1.05-2.00) had a higher risk of mortality than nonOP/nonSP participants. SP was not significantly related to mortality (HR: 1.14, 95% CI: 0.90-1.45). There was no statistical interaction between OP and SP in incident disability and mortality.

CONCLUSIONS

Among older adults, OS identified by bioimpedance and quantitative ultrasound assessments was associated with an increased risk of disability and mortality. Further research is needed to implement these findings in community health activities, such as setting precise cut-off values and constructing accurate disability and mortality prediction models.

Understanding entrance-air-kerma as a quality-control metric for dual-energy x-ray absorptiometry

Purpose

The low exposures, unique x‐ray beam geometry, and scanning design in dual‐energy x‐ray absorptiometry (DXA) make measurement and quality‐control strategies different from traditional x‐ray equipment. This study examines the dependence of measured entrance‐air‐kerma (EAK) on both dose sensor type and scan length. The feasibility of using EAK to compare scanner output between different scan modes, individual scanners, and scanner platforms was also established. Finally, the congruence between measured and vendor‐reported EAK was analyzed.

Methods

Four Hologic DXA scanners at two institutions and all four available scan modes were tested. EAK was measured directly by three types of Radcal dose sensors: 60‐cc pancake ion‐chamber (IC), 180‐cc pancake IC, and solid‐state detector. The coefficient of variation (COV) was used to assess the dependence of EAK on scan length. Variations in EAK between the types of dose sensors as well as measured versus vendor‐reported values were evaluated using Bland–Altman analysis: mean ±95% prediction interval (PI): 1.96σ.

Results

Dose sensor variations in EAK were minimal, with a −3.5 ± 3.5% (mean ±95% PI) percent difference between the two sizes of IC's. The solid‐state detector produced highly similar measurements to the 180‐cc IC. These small differences were consistent across all scanners and all scan modes tested. Neither measured nor vendor‐reported EAK values were found to show relevant dependence on scan length, with all COV values ≤4%. Differences between measured and reported EAK were higher at −6 ± 48%. Likely errors in vendor‐reported EAK calculations were also identified.

Conclusion

It is feasible to quantify DXA scanner stability using EAK as a quality‐control metric with a variety of solid‐state and IC dose sensors, and the scan length used is not critical. Although vendor‐reported EAK was consistent among scanners of the same platform, measured EAK varied significantly from scanner to scanner. As a result, measured and reported EAK may not always be comparable.

Diagnostic value of calcaneal quantitative ultrasound in the evaluation of osteoporosis in middle-aged and elderly patients

To study the correlation between calcaneal quantitative ultrasound (QUS) and dual-energy X-ray absorptiometry (DXA), and analyze the diagnostic value of calcaneal QUS in the evaluation of middle-aged and elderly osteoporosis.We assessed bone mineral density (BMD) at the femoral neck and intertrochanteric of left hip and lumbar spine (L1-L4) sites with DXA and QUS parameters of the right and left calcanei in a cohort of 82 patients over the age of 50 years. Using DXA parameters as the gold standard for the diagnosis of osteoporosis, the correlation coefficient between BMD and QUS parameters was calculated. Receiver operating characteristic curve was generated and areas under the curves were evaluated. Cut-off values for QUS were defined.In men, there was a moderate correlation between calcaneal QUS and proximal femoral BMD (P < .05), but no significant correlation between calcaneal QUS and lumbar BMD (P > .05). In women, calcaneal QUS were moderately correlated with lumbar spine and proximal femoral BMD (P < .05). Using DXA as the gold standard, the accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of calcaneal QUS in the diagnosis of osteoporosis were 90.2%, 89.2%, 100%, 100%, and 50.0%, respectively. According to the receiver operating characteristic curve, when the QUS T-score of calcaneum was -1.8, the area under the curve was 0.888, the sensitivity was 73.21%, and the specificity was 92.31% (P < .05). When the QUS T-score of calcaneum was -2.35, the sensitivity was 37.2% and the specificity was 100%.Calcaneal QUS can be used to predict proximal femoral BMD in middle-aged and elderly people, as well as lumbar BMD in women. As a screening method for osteoporosis, calcaneal QUS has good specificity, so it can be recommended to use it as a pre-screening tool to reduce the number of DXA screening. When the QUS T-score of calcaneum is -1.8, it has the greatest diagnostic efficiency for osteoporosis; when the QUS T-score of calcaneum is ≤-2.35, it can be diagnosed as osteoporosis.

Multidisciplinary team training reduces the error rate of DXA image

Establishing the hospital's own standard operating procedures (SOPs) and team training including physicians and technologists reduces the error rate of dual-energy X-ray absorptiometry (DXA) measurement. In addition, when monitoring DXA images, it is necessary to check whether region of interest (ROI) and bone mapping are properly set as well as patient positioning.

INTRODUCTION

Physicians often experience poor quality DXA images, which affects osteoporosis treatment. The purpose of this study is to analyze the change in the error rate of DXA images after a multidisciplinary team training including physicians and technologists.

METHODS

Experienced physicians and DXA technologists formed a training team to establish SOPs for DXA measurement. The training team instructed the other related hospital personnel for a month. We set the criteria of measurement errors (9 items for the lumbar spine image and 8 items for the proximal femur image). With these criteria, a total of 637 images (320 images before training and 317 images after training) were analyzed to check the frequency and distribution of errors before and after training.

RESULTS

The most common error when measuring the lumbar spine image before training was inadequate bone mapping (51.9%), and when measuring the proximal femur image was the incorrect area of the ROI of the femoral neck (37.2%). The most improved error after training was inadequate bone mapping (33.3% improvement) in the lumbar spine image and inadequate internal rotation (13.6% improvement) in the proximal femur image. Errors were significantly reduced by 23.2% in the lumbar spine, 9.0% in the proximal femur, and 9.2% in both the regions.

CONCLUSIONS

Establishing SOPs and multidisciplinary team training effectively reduced the error rate of DXA images.