Study On The Accuracy And Influencing Factors Of Lumbar Bone Mineral Density Measured By QCT And DXA In Postmenopausal Women

Part 1 Comparative study in lumbar bone mineral density measurements by quantitative computed tomography and dual-energy X-ray absorptiometry in postmenopausal womenBackgroundLevel-specific lumbar bone mineral density(BMD)evaluation of a single vertebral body can provide useful surgical planning and osteoporosis management information.Previous comparative studies have primarily focused on detecting spinal osteoporosis but not at specific levels.PurposeTo compare the detection rate of lumbar osteoporosis between quantitative computed tomography(QCT)and dual-energy X-ray absorptiometry(DXA);to explore and analyze the distribution models of QCT-derived BMD and DXA T-score at the specific levels;and to evaluate the diagnostic accuracy of level-specific BMD thresholds for the prediction of osteoporotic vertebral compression fracture(OVCF)in postmenopausal women.MethodsPostmenopausal women who underwent QCT and DXA within a week of admission from May 2019 to June 2022 were enrolled.The diagnostic criteria for osteoporosis recommended by the World Health Organization and the American College of Radiology were used for lumbar osteoporotic diagnosis.To evaluate differences in lumbar BMD measurements at specific levels,a threshold of T score=-2.5 and QCT-derived BMD=80 mg/cm~3 were used to categorize level-specific lumbar BMD into low and high BMD.Disagreements in BMD categorization between DXA and QCT were classified as a minor or major discordance based on the definition by Woodson.Data between QCT and DXA were visualized in a stacked bar plot and analyzed.Correlations between DXA and QCT at the specific levels were evaluated using Pearson’s linear correlation and scatter plots.Curve fitting of BMD distribution,receiver operating characteristic(ROC)and area under the curve(AUC)for each single vertebral level was performed.ResultsOf the 296 patients,QCT diagnosed 61.1%as osteoporosis,30.4%as osteopenia and 8.4%as normal.For those screened with DXA,54.1%of the patients had osteoporosis,29.4%had osteopenia and 16.6%had normal BMD.Diagnoses were concordant for 194(65.5%)patients.Of the other 102 discordant patients,5(1.7%)were major and 97(32.8%)were minor.Significant correlations in level-specific BMD between DXA and QCT were observed(p<0.001),with Pearson’s correlation coefficients ranging from 0.662 to 0.728.The correlation strength was in the order of L1>L2>L3>L4.The low BMD detection rate for QCT was significantly higher than that for DXA at the L3 and L4 levels(65%vs 47.9%and 68.1%vs 43.7,respectively,p<0.001).Patients with OVCF showed significantly lower QCT-derived BMD(47.2 mg/cm~3 vs 83.2 mg/cm~3,p<0.001)and T-score(-3.39 vs-1.98,p<0.001)than those without OVCF.Among these patients,82.8%(101/122)were diagnosed with osteoporosis by QCT measurement,while only 74.6%(91/122)were diagnosed by DXA.For discrimination between patients with and without OVCF,QCT-derived BMD showed better diagnosed performance(AUC range from 0.769 to 0.801)than DXA T-score(AUC range from 0.696 to 0.753).ConclusionQCT provided a more accurate evaluation of lumbar osteoporosis than DXA.The QCT-derived BMD measurements at a specific lumbar level have a high diagnostic performance for OVCF.Part 2 Comparative study on the impact of abdominal aortic calcification on dual-energy X-ray absorptiometry and quantitative computed tomography bone mineral density measurements in postmenopausal womenBackgroundPrevious studies conducted quantitative or semi-quantitative assessments of the degree of AAC in postmenopausal women and explored whether AAC influences measurements on DXA or QCT respectively,but did not simultaneously compare the BMD measurements from the two modalities in the same participant.PurposeTo assess the association between abdominal aortic calcification(AAC)in postmenopausal women and bone mineral density(BMD)obtained from quantitative computed tomography(QCT)and dual-energy X-ray absorptiometry(DXA)of the lumbar spine as well as whether age impacts the measurements from QCT and DXA.And compared the effect of AAC on the measurement of BMD on specific lumbar segments based on the average BMD measured by DXA and QCT in the 4 segments from L1 to L4.MethodsWe enrolled postmenopausal women who underwent MRI,QCT,and DXA within a week of admission from June 2019 to June 2022.The 3D CT image reconstruction-derived AAC score obtained from spine CT and the distribution of level-specific BMD measurements obtained using QCT and DXA were assessed.Tables and stacked bar plots were generated.Linear regression and binary logistic regression were used to assess the relationship between AAC and BMD.Confounding factors were adjusted in both logistic models.We also use the statistical method of paired sample T-test to explore the influence of AAC degree on BMD measurements after age stratification.In addition,we divided the average BMD of L1～L4 segments into two groups and conducted independent sample T-test to explore the effect of segmental AAC on BMD measurement of specific levels.ResultsOf the 296 included participants,143 were diagnosed with osteoporosis by DXA(48.3%women)and 181 by QCT(61,1%women).Among the participants,60.2%had AAC(AAC score>0)ranging from 0 to 56,with a median score of 2.Participants in the AAC group experienced OVCFs much more frequently than those in the non-AAC group(45.3%vs 26.3%).The observed rates of osteoporosis were 59.5%vs 43.2%in DXA and 72.4%vs 45.7%in QCT.In linear correlation analysis,model 1,model 2 and model 3 showed that the total score of AAC was negatively correlated with the BMD measured by DXA and QCT(B=-0.125,0.236<1,0.032,0.001,0.000<0.05 in DXA,B=-0.312 0.112,0.121<1,P=0.001,0.049,0.035<0.05).Binary logistic regression analysis showed that DXA and QCT were more likely to diagnose osteoporosis(OR=1.934 CI.207,3.099,P<0.006)and QCT(OR=3.120 CI,1.913,5.089(P<0.001)in the presence of AAC without adjusting interfering factors.After adjusting for age,serum creatinine,and related previous medical history,this association changed in Model 2,both DXA and QCT measurements.In model 3,after further adjustment of model 2 plus glucocorticoid,uric acid,alkaline phosphatase,calcium,phosphorus and creatinine,the adjusted odds ratio decreased from more than 1 to less than 1.After age stratification,it was found that there was no significant difference in the results of DXA and QCT between the two groups with or without AAC in the three age groups of 50 to 59 years old,60 to 69 years old and more than 70 years old(that is,the average T value measured by DXA and the average BMD measured by QCT)(0.606,0.552,0.186,0.365>0.05).In DXA measurement,except for L1 segments,there was no significant difference between AAC and non-AAC groups(P=0.114,0.052,0.600>0.05 in level L2,L3,L4,respectively)while there were significant differences in L1-L4 levels between the two groups(P<0.01 in level L1,L2,L3,L4 respectively).The average BMD of the 4 segments in the AAC group were lower than that in the non-AAC group in DXA and QCT.ConclusionThe results showed that the BMD measurements of DXA and QCT were significantly smaller in postmenopausal women with AAC.However,this difference disappears after age stratification,suggesting that age may be the cause of this difference.In clinical work,spinal surgeons need to consider the influence of patients’age when making treatment strategies for postmenopausal women with AAC..