Discordance in diagnosis of osteoporosis using spine and hip bone densitometry

Prevalence and associated factors of T-score discordance between different sites in Iranian patients with spinal cord injury

OBJECTIVES

The present study was conducted to determine the prevalence of T-score discordance and its risk factors in a group of patients with spinal cord injury in a university teaching hospital in the Iranian capital of Tehran.

METHODS

This cross-sectional study was conducted on paraplegic men undergoing bone density testing in an outpatient clinic at a hospital in the Iranian capital, Tehran, between March 2011 and 2012. A questionnaire on demographic and anthropometric characteristics, including age, height, weight, engagement in physical activity and personal smoking habits, was filled out for each subject. All the subjects underwent bone mineral density measurement and blood samples were sent for laboratory testing.

RESULTS

Major T-score discordance between two sites was noted in 54 (41.22%) patients. Multivariate logistic regression revealed that every unit increase in serum calcium levels, as the only factor influencing T-score discordance, was associated with a 2.49-fold increased risk in T-score discordance in the area. As for the spine and radius, BMI was the only influencing factor as every unit increase in BMI was associated with a 14% lower risk for T-score discordance in these regions. Body mass index was the only factor, based on the multivariate model, affecting the risk of developing T-score discordance between two sites.

CONCLUSION

Our study revealed the high prevalence of T-score discordance in patients with spinal cord injury. Physicians should therefore be encouraged to perform BMD at three sites when visiting patients with such injuries.

Lumbar spine bone mineral density in US adults: demographic patterns and relationship with femur neck skeletal status

This analysis examines lumbar spine bone mineral density (BMD) of US adults from NHANES 2005-2008 by age, sex, and race/ethnicity. Prevalence of low spine BMD and agreement between the prevalence of low BMD at the spine and femur neck in older adults are also assessed.

INTRODUCTION

Lumbar spine BMD data from a representative sample of the US population have not been previously available.

METHODS

We used data from the National Health and Nutrition Examination Survey 2005-2008 to examine demographic patterns in lumbar spine BMD among US adults age ≥20 years and the prevalence of low lumbar spine BMD in adults age ≥50 years. Agreement between the prevalence of low BMD at the femur neck and spine in older adults was also assessed. Dual-energy X-ray absorptiometry was used to measure lumbar spine and femur neck BMD. World Health Organization definitions were used to categorize skeletal status as normal, osteopenia, or osteoporosis.

RESULTS

Compared to non-Hispanic whites, non-Hispanic blacks had higher and Mexican Americans had lower lumbar spine BMD. Lumbar spine BMD declined with age in women, but not in men. Approximately 4.7 million (10%) older US women and 1 million (3%) older men had lumbar spine osteoporosis in 2005-2008. Roughly one third of them differed in skeletal status at the spine and hip but most were normal at one site and osteopenic at the other. Only 3-10%, depending on sex, had osteoporosis at one skeletal site but not at the other skeletal site. Between 76% and 87% with discordant skeletal status had lumbar spine T-scores within 1 unit of the category threshold.

CONCLUSIONS

These findings suggest that measuring either the femur neck or the lumbar spine will correctly classify the majority of individuals who present for care as osteoporotic or not.

Characterization of osteopenia/osteoporosis in adult scoliosis: does bone density affect surgical outcome?

STUDY DESIGN

Retrospective study.

OBJECTIVE

The aim of this study is to validate the prevalence of low bone mineral density (BMD) in woman patients with adult scoliosis and to relate that to surgical treatment outcome. Despite reports of the high prevalence of low BMD among female with adolescent idiopathic, these findings have not been substantiated in any comprehensive review of adult scoliosis patients undergoing surgical treatment.

SUMMARY OF BACKGROUND DATA

It has been suggested that scoliosis may predispose to osteoporosis and that degenerative scoliosis could falsely elevate spinal BMD measurements with dual energy radiograph absorptiometry (DXA). The discordance between hip and spine BMD measurement using DXA has also been shown in previous cross-sectional study for adult population.

METHODS

A retrospective review of 176 women treated surgically for scoliosis. BMD of the lumbar spine and femoral neck were determined by DXA. Patients were categorized as follows: concordance (osteoporosis, osteopenia, or normal BMD on both sites), minor discordance (osteoporosis in one site and osteopenia in the other site), and major discordance (osteoporosis in one site and normal the other site). Body mass index (BMI), preoperative Cobb angle, fusion ratio, and complication were recorded. Statistical analysis included the Student t test, χ(2) test, regression coefficient test, and simple linear regression. P value was set at P < 0.05.

RESULTS

The mean age was 51 ± 12 years (26-82 years). The mean T score of the hip was -1.23 ± 0.89 and of the spine was -0.52 ± 1.57. Major discordance in BMD 7 (4%) points, minor discordance 68 (39%) points, and concordance was 101 (57%) points. There was moderate correlation between T score of hip and spine (R = 0.55P < 0.01). T score of the hip and of the spine showed 10.8% and 10.2% of the patients were osteoporotic. The mean Z score of the hip and of the spine showed comparable age and sex matched values. No correlation was observed between BMD and Cobb angle (R = 0.05, P = 0.464). The fusion rate was 93% and surgical complication rate was 14.9%. No significant correlation was observed between BMD and fusion (P = 0.80) complication (P = 0.13).

CONCLUSION

Comparable bone density exists among adult scoliosis patients with no correlation between BMD and curve magnitude, fusion and complication rates. The difference in BMD of the hip and of spine cannot be fully explained in the review. These results will guide in surgical planning, patient selection on the treatment options.

Screening for osteoporosis: a survey of older psychiatric inpatients at a tertiary referral centre

BACKGROUND

Osteoporosis causes much morbidity and mortality among elderly people. Older inpatients with severe mental illness may be at particular risk of osteoporosis because of factors including immobility, vitamin D deficiency and psychotropic medication.

METHOD

We screened predominantly older inpatients with severe mental illness for osteoporosis using a peripheral DEXA scanner. Associations were examined between patient variables and osteoporosis as detected by DEXA scan, Z-scores and history of fragility fractures. Patients were followed up to see how many subsequently received drug treatment for osteoporosis. Patient acceptability of the scanning technique was also assessed.

RESULTS

It was possible to scan 72/89 (81%) of patients. Mean T-score was -2.79 (SD 1.50) and mean Z-score -0.76 (SD 1.34). Forty-two (58%) patients had osteoporosis and 23 (32%) osteopenia. Twelve (17%) patients with a history of fragility fractures had osteoporosis on DEXA scan. A scan suggestive of osteoporosis and a history of fragility fractures were both associated with age of 75 years and over and thoracic kyphosis. Low Z-scores were associated with longer hospital stay and osteoporosis-predisposing drugs. Patient acceptability of scanning was high. At follow-up, only 7/16 (44%) patients were suitable for central scanning and 9/40 (23%) for bisphosphonates.

CONCLUSION

Older institutional patients with severe mental illness are likely to be at high risk of developing osteoporosis. Peripheral DEXA scanning is acceptable to these patients and identifies those at high risk of fractures. Some behaviorally disturbed patients are not suitable for central scans or for some osteoporosis drug treatments.

DXA scanning in clinical practice

Dual-energy X-ray absorptiometry (DXA) is recognized as the reference method to measure bone mineral density (BMD) with acceptable accuracy errors and good precision and reproducibility. The World Health Organization (WHO) has established DXA as the best densitometric technique for assessing BMD in postmenopausal women and based the definitions of osteopenia and osteoporosis on its results. DXA allows accurate diagnosis of osteoporosis, estimation of fracture risk and monitoring of patients undergoing treatment. However, when DXA studies are performed incorrectly, it can lead to major mistakes in diagnosis and therapy. This article reviews the fundamentals of positioning, scan analysis and interpretation of DXA in clinical practice.

Discordance in diagnosis of osteoporosis using spine and hip bone densitometry

Diagnostic discordance for osteoporosis is the observation that the T-score of a patient varies between skeletal sites, falling into 2 different diagnostic categories identified by the World Health Organization classification system. Densitometrists and clinicians should expect that at least 4 of every 10 patients tested by dual-energy X-ray absorptiometry (DXA) to demonstrate T-score discordance between spine and total hip measurement sites. T-score discordance can occur for a variety of reasons related to physiologic and pathologic patient factors and the performance or analysis of DXA itself.