Bone mineral density referral for dual-energy X-ray absorptiometry using quantitative ultrasound as a prescreening tool in postmenopausal women from the general population: a cost-effectiveness analysis

Clinical Validation of a Deep Learning-Based Software for Lumbar Bone Mineral Density and T-Score Prediction from Chest X-ray Images

Screening for osteoporosis is crucial for early detection and prevention, yet it faces challenges due to the low accuracy of calcaneal quantitative ultrasound (QUS) and limited access to dual-energy X-ray absorptiometry (DXA) scans. Recent advances in AI offer a promising solution through opportunistic screening using existing medical images. This study aims to utilize deep learning techniques to develop a model that analyzes chest X-ray (CXR) images for osteoporosis screening. This study included the AI model development stage and the clinical validation stage. In the AI model development stage, the combined dataset of 5122 paired CXR images and DXA reports from the patients aged 20 to 98 years at a medical center was collected. The images were enhanced and filtered for hardware retention such as pedicle screws, bone cement, artificial intervertebral discs or severe deformity in target level of T12 and L1. The dataset was then separated into training, validating, and testing datasets for model training and performance validation. In the clinical validation stage, we collected 440 paired CXR images and DXA reports from both the TCVGH and Joy Clinic, including 304 pared data from TCVGH and 136 paired data from Joy Clinic. The pre-clinical test yielded an area under the curve (AUC) of 0.940, while the clinical validation showed an AUC of 0.946. Pearson's correlation coefficient was 0.88. The model demonstrated an overall accuracy, sensitivity, and specificity of 89.0%, 88.7%, and 89.4%, respectively. This study proposes an AI model for opportunistic osteoporosis screening through CXR, demonstrating good performance and suggesting its potential for broad adoption in preliminary screening among high-risk populations.

Establish and validate the reliability of predictive models in bone mineral density by deep learning as examination tool for women

While FRAX with BMD could be more precise in estimating the fracture risk, DL-based models were validated to slightly reduce the number of under- and over-treated patients when no BMD measurements were available. The validated models could be used to screen for patients at a high risk of fracture and osteoporosis.

PURPOSE

Fracture risk assessment tool (FRAX) is useful in classifying the fracture risk level, and precise prediction can be achieved by estimating both clinical risk factors and bone mineral density (BMD) using dual X-ray absorptiometry (DXA). However, DXA is not frequently feasible because of its cost and accessibility. This study aimed to establish the reliability of deep learning (DL)-based alternative tools for screening patients at a high risk of fracture and osteoporosis.

METHODS

Participants were enrolled from the National Bone Health Screening Project of Taiwan in this cross-sectional study. First, DL-based models were built to predict the lowest T-score value in either the lumbar spine, total hip, or femoral neck and their respective BMD values. The Bland-Altman analysis was used to compare the agreement between the models and DXA. Second, the predictive model to classify patients with a high fracture risk was built according to the estimated BMD from the first step and the FRAX score without BMD. The performance of the model was compared with the classification based on FRAX with BMD.

RESULTS

Approximately 10,827 women (mean age, 65.4 ± 9.4 years) were enrolled. In the prediction of the lumbar spine BMD, total hip BMD, femoral neck BMD, and lowest T-score, the root-mean-square error (RMSE) was 0.099, 0.089, 0.076, and 0.68, respectively. The Bland-Altman analysis revealed a nonsignificant difference between the predictive models and DXA. The FRAX score with femoral neck BMD for major osteoporotic fracture risk was 9.7% ± 6.7%, whereas the risk for hip fracture was 3.3% ± 4.6%. Comparison between the classification of FRAX with and without BMD revealed the accuracy rate, positive predictive value (PPV), and negative predictive value (NPV) of 78.8%, 64.6%, and 89.9%, respectively. The area under the receiver operating characteristic curve (AUROC), accuracy rate, PPV, and NPV of the classification model were 0.913 (95% confidence interval: 0.904-0.922), 83.5%, 71.2%, and 92.2%, respectively.

CONCLUSION

While FRAX with BMD could be more precise in estimating the fracture risk, DL-based models were validated to slightly reduce the number of under- and over-treated patients when no BMD measurements were available. The validated models could be used to screen for patients at a high risk of fracture and osteoporosis.

Clinical Conformity Between Heel Ultrasound and Densitometry in Postmenopausal Women: A Systematic Review

OBJECTIVES

To assess the conformity between heel ultrasound and densitometry, and the clinical application of densitometry T-score "gold standard" in quantitative ultrasound as a method of osteoporosis diagnosis in postmenopausal women.

METHODS

The study is a systematic review of studies published in the last 17 years in PubMed, NLM Gateway, Medline, Embase, and Cochrane Library. Calcaneal quantitative ultrasound sensitivity and specificity were analyzed with regard to densitometry measurements in postmenopausal women. In addition, we summarized the values of ultrasound T-scores, for which their accuracy in osteoporosis diagnosis is the highest.

RESULTS

The inclusion criteria met 15 research studies conducted on postmenopausal women. In 11 of them, the authors concluded that clinical conformity between heel ultrasound and densitometry is good. The recommended quantitative ultrasound T-score for osteoporosis diagnosis ranged between -1 and -3.65.

CONCLUSIONS

Heel ultrasound should be considered to be as accurate as densitometry in diagnosing osteoporosis. Nevertheless, it needs to have separate T-score ranges determined, because those used in densitometry are not adequate.

Techniques for diagnosing osteoporosis: a systematic review of cost-effectiveness studies

OBJECTIVES

The study question was whether dual-energy X-ray absorptiometry (DXA) alone is more cost-effective for identifying postmenopausal women with osteoporosis than a two-step procedure with quantitative ultrasound sonography (QUS) plus DXA. To answer this question, a systematic review was performed.

METHODS

Electronic databases (PubMed, INAHTA, Health Evidence Network, NIHR, the Health Technology Assessment program, the NHS Economic Evaluation Database, Research Papers in Economics, Web of Science, Scopus, and EconLit) were searched for cost-effectiveness publications. Two independent reviewers selected eligible publications based on the inclusion/exclusion criteria. Quality assessment of economic evaluations was undertaken using the Drummond checklist.

RESULTS

Seven journal articles and four reports were reviewed. The cost per true positive case diagnosed by DXA was found to be higher than that for diagnosis by QUS+DXA in two articles. In one article it was found to be lower. In three studies, the results were not conclusive. These articles were characterized by the differences in the types of devices, parameters and thresholds on the QUS and DXA tests and the unit costs of the DXA and QUS tests as well as by variability in the sensitivity and specificity of the techniques and the prevalence of osteoporosis.

CONCLUSIONS

The publications reviewed did not provide clear-cut evidence for drawing conclusions about which screening test may be more cost-effective for identifying postmenopausal women with osteoporosis.

Dual-energy X-ray absorptiometry versus quantitative ultrasonography in diagnosing osteoporosis in patients with refractory epilepsy and chronic antiepileptic drug use

BACKGROUND

The aim of this study was to assess the feasibility of calcaneal quantitative ultrasonography (QUS) as a screening method for increased risk of osteoporosis in a unique population of people with chronic epilepsy, intellectual disability (ID), and chronic use of antiepileptic drugs.

METHODS

A total of 205 patients from a long-stay care facility for people with epilepsy underwent dual-energy X-ray absorptiometry (DXA) and QUS of the calcaneus. T-scores for both DXA and QUS were calculated and correlated.

RESULTS

A total of 195 patients (95.1%) were successfully measured with DXA and 204 (99.5%) with QUS. High correlations were found between DXA and QUS T-scores: r = 0.666 (QUS versus T-score total femur), r = 0.631 (QUS versus T-score femur neck) and r = 0.485 (QUS versus T-score lumbar spine). All correlations were statistically significant (p = 0.01).

CONCLUSION

QUS showed a strong correlation with DXA and proved to be a feasible measuring method in a population with ID and epilepsy. Including osteopenia in the screening process increases the sensitivity of QUS to identify those patients at risk for the development of bone diseases.

Discriminative ability of heel quantitative ultrasound in postmenopausal women with prevalent low-trauma fractures: application of optimal threshold cutoff values using CART models

Quantitative ultrasound (QUS) of the heel has been proposed as a screening tool to evaluate the bone status and risk of osteoporotic fragility fractures. The aim of this study was to define threshold values of QUS that would maximize the predictive ability of this technique to discriminate subjects with fragility fractures. A cross-sectional analysis was made of a cohort of 1132 postmenopausal women with a mean age of 58 yr. A total of 361 women (31.9%) presented with a history of osteoporotic fracture. Most fractures (74.1%) were nonvertebral. For all patients, a questionnaire of osteoporosis risk factors and measurements of the heel QUS and bone mineral density at the lumbar spine and the proximal femur obtained by dual-energy X-ray absorptiometry (DXA) were assessed. Spinal radiographs were assessed for fractures and historical nonvertebral fragility fractures. Sensitivity, specificity, predictive values, likelihood ratios, and receiver operator characteristic (ROC) curve QUS values were calculated using the optimal threshold identified in the classification and regression trees (CART) models. Cutoff values calculated from the best CART model (i.e., a quantitative ultrasound index (QUI) greater than 88.5% in women aged 58 yr or older) yielded 88.8% (95% confidence interval [CI]: 81.4-93.5) for sensitivity, a negative predictive value of 93.8 (95% CI: 89.4-96.4), and 70.4% (95% CI: 64.6-75.7) for specificity. This cutoff value would obviate the need to perform DXA in 43.1% of the population. The area under the ROC curve of the best model was 0.8363 (95% CI: 0.8249-0.8477). In conclusion, QUS was shown to discriminate between women with and without a history of fragility fracture and constitutes a useful tool for assessing fracture risk. The application of decision trees (CART analyses) was helpful to define the optimal threshold QUS values.

Dietary vitamin K intake is associated with bone quantitative ultrasound measurements but not with bone peripheral biochemical markers in elderly men and women

BACKGROUND

Vitamin K may have a protective role against bone loss and osteoporotic fractures associated to aging, although data in humans are inconsistent and the mechanisms involved are still unknown. The main objective of the study was to assess the associations between vitamin K intake, bone density, bone structure quality and biochemical bone metabolism markers in elderly subjects. We also analyzed the relationship between changes in vitamin K intake and the evolution of bone quality markers after two years of follow-up.

METHODS

Cross-sectional analysis was carried out on 365 elderly subjects, 200 of whom were also included in a 2-year longitudinal follow-up study. Usual dietary intakes were assessed using a semi-quantitative 137-item food frequency questionnaire (FFQ). Vitamin K intake was estimated using the USDA database. Bone biochemical markers were measured in a subset of 125 subjects. Quantitative ultrasound assessment (QUS) was performed at the calcaneus to estimate bone mineral density (BMD), speed of sound (SOS), broadband ultrasound attenuation (BUA) and the quantitative ultrasound index (QUI).

RESULTS

Dietary intake of vitamin K was significantly associated with higher BMD and better QUS. No significant associations were found between vitamin K intake and bone biochemical markers. Those subjects who increased their vitamin K intake showed a lower loss of BMD, a lower decrease in SOS and a nonsignificant increase in BUA.

CONCLUSIONS

High dietary vitamin K intake was associated with superior bone properties. Moreover, an increase in dietary vitamin K was significantly related to lower losses of bone mineral density and smaller increases in the porosity and elasticity attributed to aging, which helps to explain the previously described protective effect of vitamin K intake against osteoporotic fractures.

CORRELATION BETWEEN CALCANEAL BONE ULTRASOUND MEASUREMENTS AND DENSITOMETRY AMONG POSTMENOPAUSAL WOMEN WITH FRACTURES CAUSED BY BONE FRAGILITY

Objective: To assess the correlation between ultrasound (US) measurement on the calcaneus and bone densitometry (DEXA), among postmenopausal women who already presented fragility fractures. Methods: 35 postmenopausal women over 40 years of age, with the ability to walk and presenting osteoporotic fractures of the wrist or spine, without previous treatment for osteoporosis, were analyzed in a retrospective cohort. Of these, 16 were under 60 and 19 were over 60. The broadband ultrasound attenuation (BUA) and speed of sound (SOS) were compared using DEXA (L1-L4, total femur, femoral neck and wrist). Two different values of BUA were used as cutoff points for osteoporosis: BUA < 60 dB/MHz and BUA < 64 dB/MHz (P < 0.05); and SOS < 1600 m/s. The confidence interval was 95%. The DEXA and US data were plotted on dispersion graphs and, through linear regression, it was possible to establish correlations. Following this, the sample was stratified according to age (up to 60 years and 60 years and over). Thus, the values were again compared and correlated. Results: The best correlation obtained between DEXA and US was between the T-score of the wrist and BUA < 64 dB/MHz, with 92% sensitivity and 95% specificity. Better sensitivity at all DEXA sites was obtained when US was performed on patients over 60 years of age. The SOS compatible with osteoporosis was < 1592.5 m/s (89% sensitivity and 85% specificity). Conclusion: US on the calcaneus can be used for screening the risk of osteoporosis fractures, using a cutoff of BUA < 64 dB/MHz, especially among patients over 60 years of age.

Genistein effects on quantitative ultrasound parameters and bone mineral density in osteopenic postmenopausal women

This study aimed at evaluating the effects of genistein (54 mg/die) on calcaneus and phalanges ultrasound (QUS) parameters and bone mineral density in osteopenic postmenopausal women. We concluded that genistein prevented bone loss in the osteopenic postmenopausal women and improves QUS parameters at the calcaneus and phalanges.

INTRODUCTION

The purpose of the study was to evaluate the effects of genistein (54 mg/die) on quantitative ultrasound (QUS) parameters of the calcaneus and hand phalange and on bone mineral density (BMD) in osteopenic postmenopausal women.

METHODS

One hundred thirty-eight women (age 49-67 years) were assigned to receive genistein or placebo. Bone status was assessed by measuring the anteroposterior lumbar spine and femoral neck BMD by dual energy X-ray absorptiometry and by ultrasound of the calcaneus (Achilles Plus, GE, Lunar) and of the phalanges (Bone Profiler. IGEA) at baseline and after a 1- and 2-year treatment.

RESULTS

At the end of the experimental period, genistein had significantly increased BMD in the femur and lumbar spine (p < 0.001). The stiffness index, amplitude-dependent speed of sound, and bone transmission time in the genistein group had increased significantly at the end of study (+5.3, p < 0.001; +3.6%, p < 0.001; +4.6, p < 0.001, respectively).

CONCLUSIONS

This study confirms that genistein prevented bone loss in the osteopenic postmenopausal women and it improves the QUS parameters.

The Osteoporosis Self-Assessment Tool versus alternative tests for selecting postmenopausal women for bone mineral density assessment: a comparative systematic review of accuracy

SUMMARY

We performed a systematic review of studies comparing the Osteoporosis Self-Assessment Tool (OST) and other tests used to select women for bone mineral density (BMD) assessment. In comparative meta-analyses, we found that the accuracy of OST was similar to other tests that are based on information from the medical history. By contrast, assessment by quantitative ultrasonography at the heel was more accurate than OST in discriminating between women with high and low BMD. The methodological quality of the included studies was generally low.

INTRODUCTION

Numerous tests are suggested for triaging postmenopausal women for bone mineral density (BMD) assessment by dual-energy X-ray absorptiometry. Previous studies suggest that OST, based on age and weight only, may be as accurate as more complex triage tests. We systematically compare the accuracy of OST and alternative triage tests in postmenopausal women.

METHODS

We searched PubMed, Embase, Web of Science, citation lists, and conference proceedings. Our main measure of accuracy was the diagnostic odds ratio (DOR). We compared summary estimates of DOR (sDOR) for OST and alternative tests in pairwise meta-analyses by using the Moses-Littenberg approach.

RESULTS

Summary estimates of DOR for OST and the clinical decision rules Simple Calculated Osteoporosis Risk Estimation (SCORE) and Osteoporosis Risk Assessment Instrument (ORAI) did not differ significantly in white women (relative sDOR: 0.57-1.17, all p >or= 0.11). By contrast, sDOR was higher for Stiffness Index assessed by calcaneal quantitative ultrasonography than for OST (relative sDOR: 1.9, p = 0.005). Studies were few in Asian and black women. Methodological quality, assessed with the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) checklist, was generally low.

CONCLUSIONS

In white women, the accuracy of OST and alternative clinical decision rules was similar, whereas Stiffness Index was more accurate than OST. Low study quality renders transferability to clinical settings uncertain.

Cost effectiveness of ultrasound and bone densitometry for osteoporosis screening in post-menopausal women

BACKGROUND

According to a new German guideline, decisions about bisphosphonate treatment for post-menopausal women should be based on 10-year fracture risk, and bone density should be measured by dual x-ray absorptiometry (DXA). Recently, there has been growing interest in quantitative ultrasound (QUS) as a less expensive screening alternative.

OBJECTIVE

To determine the cost effectiveness of osteoporosis screening with QUS as a pre-test for DXA and treatment with alendronate compared with (i) immediate access to DXA and (ii) no screening in women of the general population aged 50-90 years in Germany.

METHODS

A cost-utility analysis and a budget impact analysis were performed from the perspective of the statutory health insurance (SHI). A Markov model with a 1-year cycle length was used to simulate costs and benefits (QALYs), discounted at 3% per annum, over a lifetime. The number of women correctly diagnosed by QUS and DXA as being above a 10-year risk of > or =30% was estimated for different age groups (50-60, 60-70, 70-80 and 80-90 years, respectively). The robustness of the results was tested by a probabilistic Monte Carlo simulation.

RESULTS

Compared with no screening, the cost effectiveness of QUS plus DXA was found to be Euro 3529, Euro 9983, Euro 4382 and Euro 1987 per QALY for 50-, 60-, 70- and 80-year-old women, respectively (year 2006 values). This screening strategy results in annual costs of Euro 96 million or 0.07% of the SHI's annual budget. The cost effectiveness of DXA alone compared with DXA plus QUS is Euro 5331, Euro 60, 804, Euro 14, 943 and Euro 3654 per QALY for 50-, 60-, 70- and 80-year-old women, respectively. DXA alone results in a higher number of QALYs in all age groups. The results were robust in the sensitivity analysis.

CONCLUSION

Compared with no screening, the cost effectiveness of QUS and DXA in sequence is very favourable in all age groups. However, direct access to DXA is also a cost-effective option, as it increases the number of QALYs at an acceptable cost compared with pre-testing by QUS (except for women aged 60-70 years). Therefore, QUS as a pre-test for DXA can be clearly recommended only in women aged 60-70 years. For the other age groups, the cost effectiveness of QUS as a pre-test depends on the global budget constraint and the accessibility of DXA.

Cost effectiveness of screen-and-treat strategies for low bone mineral density: how do we screen, who do we screen and who do we treat?

Bone densitometry is currently widely recommended for, and considered central to, identifying post-menopausal women and older men at high risk of fracture and establishing an indication for pharmacological fracture-prevention therapy. The purpose of this article is to comprehensively review cost-effectiveness modelling studies published to date of bone mass measurement technologies (primarily dual energy x-ray absorptiometry [DXA]) designed to identify those individuals at sufficiently high risk of fracture to warrant pharmacological fracture-prevention therapy.Based on older paradigms of the pharmacological treatment of those with a bone density value below a specific threshold, bone densitometry appears to be cost effective for post-menopausal women aged > or =65 years, regardless of the presence or absence of other clinical risk factors. For younger post-menopausal women, bone densitometry is likely to be cost effective only for those with specific clinical risk factors, such as prior fracture or low bodyweight. For older men, bone densitometry may be cost effective for those who have had a prior fracture and/or are aged > or =80 years, but the subset of men for whom bone densitometry is likely to be cost effective may vary from country to country depending on societal willingness to pay for health benefits, fracture rates in the population and the costs of bone densitometry and drug treatment. The cost effectiveness of other technologies such as heel ultrasound, peripheral DXA and quantitative CT remains uncertain.However, in the context of the new WHO paradigm of directing treatment based on absolute fracture risk rather than bone density, a new generation of cost-effectiveness modelling studies will be required to define the most cost-effective way bone densitometry can be used to identify those who are likely to benefit sufficiently from pharmacological fracture-prevention therapies.

Is discordance in bone measurements affected by body composition or anthropometry? A comparative study between peripheral and central devices

Screening of osteoporosis using peripheral bone measurements has become more common, even though diagnostic discrepancies are known to exist between peripheral dual-energy X-ray (pDXA) or quantitative ultrasound (QUS) and central DXA measurements. Values of diagnostic parameters such as bone mineral density, speed of (ultra)sound, and broadband ultrasound attenuation are affected by bone size and soft tissue composition. However, their significance for the discordance between peripheral and central techniques is unclear. In this study, bone status and total body composition of 139 women (mean age 68.3 yr [1.7 SD], mean body mass index 26.5 kg/m2 [3.6 SD]) were assessed by 3 GE Lunar devices. Heel pDXA and heel QUS were conducted using peripheral instantaneous X-ray imaging (PIXI) and Achilles, respectively, and central DXA measurements were taken at the posterior-anterior lumbar spine (L2-L4) and at the left femoral neck using Prodigy. Positive significant associations were found between body height or fat (%) and most DXA or QUS parameters. The discordance between the site-dependent DXA or QUS T-score values typically increased (p<0.05) as a function of body weight or fat (%), but not with body height. On an average, body adiposity accounted for less than 11% of the differences between the techniques; however, increase of total body fat from 20% to 45% led to a discrepancy of one T-score between DXA(HEEL) and QUS(HEEL). To avoid diagnostic bias, comparative assessment of the devices using the same population is recommended.

Application of a triage approach to peripheral bone densitometry reduces the requirement for central DXA but is not cost effective

A method proffered for the interpretation of measurements from peripheral dual energy X-ray absorptiometry (pDXA) is a triage approach to stratify patients into one of three risk categories; (i) high-treat, (ii) medium-refer for central DXA and (iii) low-reassure. The aim of this study was to apply the triage approach to measures from peripheral scanners and risk indices and stratify patients into one of three risk categories (i), (ii) or (iii). 207 post-menopausal women had central DXA from which they were categorised as non-osteoporotic or osteoporotic. Additional peripheral scans of the left calcaneus were performed on three scanners (GE Lunar Achilles and PIXI, McCue CubaClinical). From demographic details four risk indices were calculated and algorithms combining measures from peripheral scanners and one risk index were obtained. All peripheral measures, risk indices and combination algorithms were good at identifying women at risk of osteoporosis (ROC areas: 0.67-0.82). Each tool stratified varying numbers of osteoporotic and non-osteoporotic women into each risk category using the triage approach. One combination algorithm (PIXI & osteoporosis indices of risk (OSIRIS)) performed best by minimising misclassification (10% non-osteoporotic, 10% osteoporotic) and reducing requirement for central DXA to 36%. However the cost of implementing the triage approach for PIXI & OSIRIS was greater (263%) than central DXA (100%) scanning all women. Although the triage approach was an effective tool at identifying women at risk of osteoporosis the unnecessary treatment of non-osteoporotic women in the high risk category make it impractical. Therefore an alternative more cost-effective method has been suggested.

Relationship between bone quantitative ultrasound and fractures: a meta-analysis

The relationship between bone QUS and fracture risk was estimated in a systematic review of data from 14 prospective studies of 47,300 individuals and 2350 incident fractures. In older women, low QUS values were associated with overall fracture risk, low-trauma fractures, and with hip, forearm, and humerus fractures separately.

INTRODUCTION

Bone quantitative ultrasound (QUS) has emerged as a promising technique to evaluate bone status. The aim of this study was to determine the association between measurements of QUS with the risk of fracture.

MATERIALS AND METHODS

A meta-analysis of prospective cohort studies published between 1985 and June 2005 with a baseline measurement of QUS and subsequent follow-up for fractures was carried out. Fourteen separate study populations, consisting of about 47,300 individuals (85.4% women), with about 124,000 person-years of observation and over 2350 fractures, including 653 hip, 529 forearm, and 386 humeral fractures, were analyzed. The main outcome measure was the estimated relative risk of fracture for a decrease in bone QUS parameters of 1 SD below sex- and age-adjusted mean in women.

RESULTS

Eleven studies evaluated QUS at the heel, with patella and phalanx (two studies each) and distal radius (one study) being scarcely used. There was not significant heterogeneity among the studies included in the review. Relative risk estimates (95% CI) for overall fractures were 1.55 (1.35-1.78) for each SD decrease in broadband ultrasound attenuation (BUA), 1.63 (1.37-1.93) for speed of sound (SOS), and 1.74 (1.39-2.17) for QUS index/stiffness index (QUI/SI). Risk estimates were similar or slightly higher for hip fractures and low-energy trauma fractures. Humeral and forearm/wrist fractures were also related with lower QUS values.

CONCLUSIONS

Measurements of bone QUS are significantly associated with nonspinal fracture risk in older women in a similar degree to DXA. QUS may be a valid alternative to evaluate fracture risk in situations where DXA is not accessible.