Relationship Between Serum Vitamin B₁₂ And Noradrenaline Levels And Orthostatic Intolerance In Children

Objective:To investigate the relationship between serum vitamin B₁₂(VitB₁₂)and noradrenaline（NA）levels and orthostatic intolerance（OI）in children.Methods:Using prospective research methods,inpatients who were diagnosed as OI for syncope or presyncope in the department of Pediatric Cardiology at the Second Hospital of Lanzhou University from April 2018 to December 2019 were studied.At the same time,healthy children who were examined in the pediatric clinic were selected as the control group.According to the results of head-up test（HUT）/head-up tilt test（HUTT）,the study subjects were divided into vasovagal syncope group（VVS）and postural tachycardia syndrome group（POTS）,of which vasovagal syncope group was divided into vasoinhibitory（VVS-VI）,cardioinhibitory（VVS-CI）and Mixed-inhibitory（VVS-MI）;According to the clinical symptoms,the research subjects were divided into presyncope group and syncope group,then the syncope group was further divided into the occasional syncope group and the frequent syncope group according to the frequency of syncope.All children were collected for fasting venous blood to detect serum VitB₁₂,NA and VitB₁₂2 biomarker methylmalonic acid（MMA）levels（enzyme-linked immunosorbent assay）.SPSS 22.0 software was used for data statistical processing and analysis.Results:（1）The levels of serum VitB₁₂2 and NA in the OI group were lower than the control group（P<0.05）,and the serum MMA level was higher than the control group（P<0.05）,but there were no differences in the three levels among OI subtypes（P>0.05）;（2）Serum VitB₁₂2 and NA levels in the syncope group were significantly decreased（P<0.05）and MMA level was increased（P<0.05）,but there were no statistically significant differences between different syncope frequencies（P>0.05）;.（3）Serum VitB₁₂2 of OI children was positively correlated with NA levels,but significantly negatively correlated with MMA levels,both of which were statistically significant（P<0.05）.（4）The binary logistic regression analysis showed that the decrease of serum VitB₁₂,NA level and the increase of MMA level were related risk factors for OI.（5）The receiver operating characteristic（ROC）curve analysis showed that serum VitB₁₂2 was 378.5 pg/mL,serum NA was 144.35 ng/L and serum MMA was390.65 pg/mL,the sensitivity and specificity of predicted OI were respectively 68.1%and 87.7%,33.6%and 96.5%,85.3%and 91.2%.The combination of the three predicts OI with a sensitivity of 89.7%and a specificity of 93%.Conclusion:（1）Decreased serum VitB₁₂2 and NA levels are independent risk factors for the occurrence of OI,and involve in the occurrence of sympathetic dysfunction and pathophysiological processes;（2）Serum VitB₁₂2 combined with NA and MMA has a great value in predicting OI,which has certain clinical guiding significance.