A Preliminary Study On PNfL As A Biomarker For Diagnosis And Progression Of MSA

Background:Multiple system atrophy(MSA)is an adult-onset neurodegenerative disease which progresses rapidly.It is difficult to diagnose and needs to be distinguished from many diseases including Parkinson’s disease(PD),progressive supranuclear palsy(PSP),sporadic adult-onset ataxia(SAOA),etc.The high rate of clinical misdiagnosis has greatly affected the formulation of disease treatment strategies,however there is still a lack of reliable and effective biomarkers to assist the clinical diagnosis of MSA.At present,the semi-quantitative unified multiple system atrophy rating scale(UMSARS)is mainly used to evaluate the disease severity of MSA patients.There are no sensitive or objective biomarkers that can accurately reflect the disease severity of MSA.Therefore,identifying biomarkers which could assist the diagnosis and reflect the progress of MSA is of great value for accurate prediction of disease progression,clinical management and treatment.Neurofilament light chain(Nf L)is a specific component of nerve axons,which can be released into tissue fluid,cerebrospinal fluid and blood after nerve axon injury or death.In other neurodegenerative diseases such as PD and Alzheimer’s disease(AD),blood Nf L has been proved to be a reliable biomarker for disease diagnosis and prediction of disease progression,while analogous researches on it as a biomarker for MSA are quite limited.Objective:To explore the value of plasma Nf L(p Nf L)as a biomarker of MSA disease diagnosis and severity evaluatio n.To analyze the trajectory characteristics of p Nf L concentration along with the progression of MSA disease and explore its role in predicting the progression of MSA disease.Methods:1.A cross-sectional study was conducted in 214 patients diagnosed as probable or possible MSA,65 PD patients and 211 healthy controls(HC).The p Nf L levels of MSA,PD patients and HC were measured by single molecule array(Simoa).The disease severity of MSA patients was evaluated by UMSARS,scales for outcomes in Parkinson’s disease-autonomic questionnaire(SCOPA-AUT),Wexner continence grading scale(Wexner),minimental state examination(MMSE)and frontal assessment battery(FAB).The relationship between p Nf L concentration and age was analyzed by Spearman correlation,linear regression and quadratic regression.The difference of p Nf L concentration among groups was compared by nonparametric Kruskal-Wallis test,nonparametric covariance analysis and ternary multivariate logistic regression analysis.The diagnostic efficacy of p Nf L concentration was evaluated by receiver operating characteristic curve(ROC),and the correlation between p Nf L concentration and clinical characteristics was analyzed by Spearman correlation and partial correlation.2.Conducting a cohort study,84 MSA patients in the baseline study were longitudinally visited at intervals of more than half a year.The p Nf L concentration of MSA patients during the visit period was also detected through Simoa,and the disease severity was mainly evaluated by UMSARS and SCOPA-AUT.Mixed linear model and mixed quadratic nonlinear model were used to analyze the trajectory characteristics of clinical scores and p Nf L concentration along with the duration progression of disease in MSA patients,respectively.The mixed linear model was used to analyze the factors affecting the progress of patients’ clinical scores,and the factors were ranked by random forest model.Based on the related factors,univariate and multivariate logistic models were used to predict the progress rate of clinical scores,whose diagnostic efficiency was evaluated by ROC curve.The sample size simulation method based on mixed linear model was used to estimate the sample size of clinical trials.Results:1.Results of cross-sectional study:(1)In all study groups,there was a linear relationship between p Nf L concentration and age(MSA: β=0.628,p=0.004;PD: β=0.723,p=0.034;HC:β=0.443,p<0.001).(2)The median p Nf L concentration of MSA group,PD group and HC group was 35.949(6.991～171.690)pg/ml,15.952(3.590～172.516)pg/ml and 10.268(1.961～102.836)pg/ml.The analysis of inter-group difference showed that the concentration of p Nf L in MSA group was significantly higher than that in PD group(p<0.001)and HC group(p<0.001),and p Nf L concentration in PD group was significantly higher than that in HC group(p=0.043).The results of subgroup analysis showed that the p Nf L concentration in MSA-P group was significantly higher than that in PD group(p<0.001),but there was no significant difference in p Nf L concentration between MSA-C group and MSA-P group(p=0.698),as well as between probable MSA group and possible MSA group(p=0.478).(3)The results of ROC curve showed that p Nf L concentration could distinguish MSA from HC,MSA from PD,MSA-P from PD well,and the area under the ROC curve(AUC)after adjusting age was 0.950,0.867 and 0.852,respectively.But the diagnostic efficiency of p Nf L distinguishing PD from HC was not good,and the AUC value after adjusting age was only 0.694.(4)The results of correlation analysis showed that the p Nf L concentration was significantly positive correlated with UMSARS-I score(r=0.315,p<0.001),UMSARS-Ⅱ score(r=0.278,p<0.001),UMSARS-Ⅳ score(r=0.236,p<0.001),UMSARS total score(r=0.304,p<0.001)and SCOPA-AUT score(r=0.290,p<0.001)in MSA patients,while it has no significant correlations with the duration of disease,Wexner score,MMSE score or FAB score.2.Results of cohort study:(1)The results of trajectory analysis indicated that the UMSARS-I score(β=2.594,p<0.001),UMSARS-Ⅱ score(β=3.626,p<0.001),UMSARS total score(β=6.590,p<0.001)and SCOPA-AUT score(β=2.974,p<0.001)of MSA patients all progressed linearly with the duration of disea se.On the whole,the concentration of p Nf L also increased linearly with the duration of disease,but it did not always increase with the disease progression.In some patients,p Nf L concentration showed a downward trend(β=1.085,p=0.259).(2)The results of mixed linear model analysis and importance ranking in random forest model showed that p Nf L concentration at baseline was significantly correlated with the progress of UMSARS-I score(β=0.028,p=0.010),UMSARS-Ⅱ score(β=0.041,p=0.003),UMSARS total score(β=0.074,p=0.003)and SCOPA-AUT score(β=0.045,p<0.001)in MSA patients,and that was the most important predictor of score progression.However,the change rate of p Nf L concentration had no significant effect on the progress of clinical scores in MSA patients(p>0.05).(3)The results of ROC curve suggested that p Nf L concentration at baseline had certain predictive value in predicting the fast or slow progression trend of UMSARS-Ⅱ(AUC=0.710)score and UMSARS total score(AUC=0.723),but was less effe ctive in predicting that of UMSARS-I score(AUC=0.652)and SCOPA-AUT score(AUC=0.667).Combining other potential factors such as subtypes and baseline Hoehn-Yahr stage can further improve the diagnostic efficiency.(4)Estimation of sample size in clinica l trials: assuming that the effect size of the trial is 0.2,in order to achieve a statistical effect of 80%,the sample size of MSA patients required for a one-year trial is about 136,376,174 and 98 respectively,and the sample size of MSA patients need ed for a two-year trial is about 38,114,54 and 32 respectively,based on UMSARS-I score,UMSARS-Ⅱ score,UMSARS total score and SCOPA-AUT score.Conclusion:1.The level of p Nf L in MSA patients is significantly higher than that in healthy controls and PD patients,suggesting that it can be used as a biomarker for diagnosis of MSA.2.The level of p Nf L in MSA patients is significantly correlated with the severity of the disease,suggesting that it can be used as a biomarker of the severity o f MSA.3.Baseline p Nf L level is significantly correlated with the progression of disease severity in MSA patients,which can help predict the progression of MSA disease severity.Combined with subtypes,baseline Hoehn-Yahr stage,etc.,the predictive efficiency can be further improved.4.This study firstly found that there was no significant correlation between the change rate of p Nf L concentration and the progression of disease severity in MSA patients,indicating that the change rate of p Nf L concentration has no significant predictive value for the progression of disease severity in MSA patients.5.This study provides a reference of sample size for the future clinical trials of MSA patients in the mainland of China for the first time.