| Objective:Dialysis patients are at risk for muscle mass loss and functional loss because of associated malnutrition,chronic inflammation,and reduced exercise,and the prevalence of sarcopenia.As an important evaluation index of sarcopenia,muscle mass is an important factor reflecting the prognosis of dialysis patients.However,there are few studies to evaluate the relationship between muscle mass and the prognosis of dialysis patients.It is often evaluated by dual-energy X-ray absorptiometry(DXA)and bioelectrical impedance analysis(BIA).The standard for evaluating muscle quality by computed tomography(CT)has not been established.We aimed to explore the predictive value of chest and abdominal CT image analysis of muscle mass in the prognosis of dialysis patients.Methods:The study was a multicenter retrospective cohort study that analyzed CT images of 311 initial dialysis patients(31 lost,9.97%)from four centers between January 2014 and December 2017.Outcomes were cardiac death,all-cause death,and completion of a 3-year follow-up.CT images of the first lumbar vertebra(L1)level and the third lumbar vertebra(L3)level can reflect the muscle quality of the body to a certain extent.Image J software was used to obtain the data of skeletal muscle index(SMI,cm~2/m~2)and skeletal muscle density(SMD,HU)of L1 and L3 level.Low SMD(SMD<36.98 HU,n=163)was diagnosed based on the optimal cutoff value of the receiver operating characteristic(ROC)curve,while SMI was not significant.Cox regression models were used to investigate the risk factors of death.Kaplan-Meier analysis and Nomogram analysis were used to quantify risks.The agreement between SMI and SMD of L1 and the corresponding data of L3 was investigated by scatter plots.Results:280 patients(31/311 lost)were involved in the study,in which 22 developed cardiac death(7.86%),and 49 developed all-cause death(17.50%).Among the non-cardiac deaths,16 patients died of infection-related factors(59.26%),11 of which were low SMD group(68.75%).The incidence of cardiac death(P=0.0024)and all-cause death(P=0.0014)were significantly higher in low SMD group than in the high SMD group.Multivariate Cox regression models indicated that low SMD was an independent risk factor of all-cause mortality(HR:0.34,95%CI:0.17～0.67,P=0.0018).In the adjusted model,low SMD was proved to be an independent risk of death(cardiac death,HR:0.20,95%CI:0.08～0.50,P=0.0006;all-cause death,HR:0.42,95%CI:0.26～0.68,P=0.0005).There was a high agreement between L1 and L3SMD(Spearman correlation coefficient:0.68268,Pearson correlation coefficient:0.68268,P<0.0001)and SMI(Spearman correlation coefficient:0.83327,Pearson correlation coefficient:0.74607,P<0.0001).Conclusion:In the dialysis population,CT-determined skeletal muscle mass is helpful to identify sarcopenia and judge prognosis.In this study,half of dialysis patients had low SMD,and low SMD was independently associated with cardiac death and all-cause death.In the absence of abdominal CT examination(L3 level data),chest CT examination(L1 level data)might be helpful to identify patients with low SMD. |
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