Discordance in diagnosis of osteoporosis by quantitative computed tomography and dual-energy X-ray absorptiometry in Chinese elderly men

Abstract

Objective: The objective of this study was to investigate the diagnostic discordance of osteoporosis by quantitative computed tomography (QCT) and dual-energy X-ray absorptiometry (DXA) in Chinese elderly men.

Methods: A total of 313 males older than 60 years, who underwent both spinal QCT and lumbar spine and hip DXA in our department, were included. The diagnostic criteria established by the World Health Organisation in 1994 were used for DXA to diagnose osteoporosis, and the criteria recommended by the International Society of Clinical Densitometry were used for QCT. The osteoporosis detection rate by the two techniques was calculated, and the difference was compared. The minor discordance was considered present when the different diagnostic classes between the two techniques were adjacent. Major discordance was present when the diagnosis by one technique was osteoporosis and the other was normal. The computed tomography images were reviewed by radiologists to assess whether vertebral fracture, aorta calcification or degeneration was present.

Results: In the 313 participants (mean age, 79.6 ± 7.2 years), the osteoporosis detection rate was 10.9% for DXA (lumbar spine and hip) and 45.1% for QCT, a significant difference (p < 0.001). The major discordance, minor discordance and concordance of diagnosis between the two techniques were seen in 8.3%, 50.8% and 40.9%, respectively. QCT detected osteoporosis better than DXA. The causes of this discordance were degeneration of spine, abdominal aorta calcification and vertebral fractures.

Conclusion: Our study demonstrated that discordance was common when using QCT and DXA to diagnose osteoporosis and that spinal degeneration, aorta calcification and fracture obscure the bone mineral density measurement of spine by DXA. QCT is a more sensitive method of choice to identify osteoporosis in elderly Chinese men.

The translational potential of this article: This study investigated the diagnostic discordance of osteoporosis by quantitative computed tomography (QCT) and dual-energy X-ray absorptiometry (DXA) in Chinese elderly men. The results demonstrated that QCT is a more sensitive method of choice to identify osteoporosis in elderly Chinese men. This work may help clinicians make an appropriate choice of technique for the accurate diagnosis of osteoporosis and identify the patients at high risk of osteoporosis who should be treated early to prevent fractures. This may influence the therapeutic plan and the overall prognosis of patients.

Keywords: Bone mineral density; Dual X-ray absorptiometry; Osteoporosis; Quantitative computed tomography.

Figure 1

(A) An 82-year-old patient; the T-scores for lumbar spine DXA and hip DXA were 1.45 and −2.35, respectively, and the diagnosis by DXA was osteopenia. The BMD measured by QCT was 34.0 mg/cm³, the diagnosis by QCT was osteoporosis and the diagnostic discordance was minor discordance. The image obtained by QCT showed compression fracture of L1 and AAC. (B) A 70-year-old patient; the T-scores for lumbar spine DXA and hip DXA were −1.36 and −1.92, respectively, and the diagnosis by DXA was osteopenia. The BMD measured by QCT was 37.5 mg/cm³, the diagnosis by QCT was osteoporosis and the diagnostic discordance was minor discordance. The image obtained by QCT showed multiple vertebral compression and fractures and AAC. (C) An 81-year-old patient; the T-scores for lumbar spine DXA and hip DXA were 1.01 and 0.38, respectively, and the diagnosis by DXA was normal. The BMD measured by QCT was 76.2 mg/cm³, the diagnosis by QCT was osteoporosis and the diagnostic discordance was major discordance. The image obtained by QCT showed osteophytes, ossification of anterior longitudinal ligament and AAC. (D) a 72-year-old patient, the T-scores for lumbar spine DXA and hip DXA were −1.52 and −2.65, respectively, and the diagnosis by DXA was osteoporosis. The BMD measured by QCT was 126.2 mg/cm³, the diagnosis by QCT was normal and the diagnostic discordance was major discordance. AAC = abdominal aortic calcification; BMD = bone mineral density; DXA = dual-energy X-ray absorptiometry; QCT = quantitative computed tomography.