Analysis Of The Change Characteristics And Influencing Factors Of D-Dimer Levels In Premature Infants In The Early Stage Of Life

ObjectivesTo study the variation characteristics of early postnatal D-dimer（D-D）levels within 48 hours of birth in preterm infants of different gestational ages and their influencing factors,and to explore the D-D/Fibrin or fibrinogen degradation product（FDP）ratio and D-D/Fibrinogen（FIB）ratio’s practical value for assessing coagulation abnormalities in preterm infants.Offering a basis for the early diagnosis and treatment of coagulation and fibrinolytic dysfunction abnormalities in preterm infants.MethodsThe study selected premature infants who were born in the department of obstetrics of the First Affiliated Hospital of Kunming Medical University from December 2019 to August 2022 and transferred to the neonatal intensive care unit（NICU）within 24 hours after birth,and whose fibrinolytic function had completed within 48 hours after birth.Collecting basic information about premature infants,maternal information,and delivery information,coagulation-related data in preterm infants,including coagulation and fibrinolysis screening results within 48 hours after birth,and clinical information such as early onset of bleeding and coagulation diseases in newborns.Through retrospective study:Firstly,analyzing the characteristics and differences of early postnatal D-D levels in preterm infants of different gestational ages.According to their gestational age,the population was divided into four groups:late preterm infants(gestational age34-36⁺⁶weeks),moderate preterm infants(gestational age 32-33⁺⁶weeks),very preterm infants(gestational age 28-31⁺⁶weeks),extremely preterm infants(gestational age≤27⁺⁶weeks).Quartiles are used to characterize the distribution of levels of D-D.The Kruskal-Wallis test was used for the multi-group comparison,and the Bonferroni test was used for the pairwise comparison.Secondly,exploring the influencing factors of elevated plasma D-D levels in preterm infants.A case-control study was used and the study population was divided into the D-D elevated group（D-D≥2 mg/L）and the control group（D-D<2 mg/L）.The chi-square test was used,and univariate analysis of different influencing factors was performed,respectively.Factors with P<0.1 in the above analysis and factors considered to be related to the significant increase in D-D in clinical studies were included,and multivariate Logistic Regression Analysis was performed to analyze the risk factors for significant increase in D-D.Thirdly,exploring the value of D-D/FDP and D-D/FIB ratios in early clinical outcomes in preterm infants.A case-control study was used,grouping according to the early outcome of infants,and using nonparametric tests to analyze the differences between D-D/FDP,D-D/FIB ratios,D-D,FDP,and FIB levels between different outcome groups.For the indicators that were meaningful to the difference,the receiver operating characteristic curves（ROC）were plotted,the area under the curve（AUC）was calculated.To analyze the value of different indexes in evaluating the occurrence of early clinical outcomes such as coagulation in premature infants.This study uses SPSS 25.0 software package for statistical analysis.Statistical tests were considered statistically significant at P<0.05.Results1.Basic information of hospitalized preterm infants:A total of 489 premature infants were enrolled in the study,the median D-D level in different gestational age groups were>0.5 mg/L.In the gestational range of 28-31⁺⁶weeks,the D-D level was gradually decreased with the increase of gestational age.There was a significant difference in D-D levels within 48 hours of birth between different gestational age groups of preterm infants（P<0.001）.2.Multivariate Logistic regression analysis was used to analyze the factors influencing significant elevated early plasma D-D levels in preterm infants:the younger the gestational age,the higher the risk of significantly increasing plasma D-D levels in early preterm infants,and when the gestational age group of 34-32⁺⁶weeks was used as a control,preterm infants with gestational age≤31⁺⁶weeks are at increased risk of significantly elevated D-D levels（OR=2.532,95%CI 1.423-4.506,P<0.05）,which could contribute to a 0.929-fold increased risk of elevated D-D in preterm infants.Abnormal umbilical artery blood gas increased the risk of significantly elevated D-D levels（OR=3.011,95%CI 1.152-7.871,P<0.05）,which could contribute to a 1.102-fold increased risk of elevated D-D in preterm infants.Premature placental abruption increased the risk of significantly elevated D-D levels（OR=3.389,95%CI 1.085-10.592,P<0.05）,which increased the risk of significantly elevated D-D in preterm infants by 1.221-fold.Vaginal delivery increased the risk of significantly elevated D-D levels（OR=4.205,95%CI 2.676-6.607,P<0.001）,which increased the risk of significantly elevated D-D in preterm infants by 1.436-fold.3.Among the early outcomes of preterm infants,the early plasma D-D levels were higher in the in the Neonatal respiratory distress syndrome（NRDS）group with positive outcome than that in the negative outcome group（P<0.05）,and the D-D/FIB ratio was lower than that in the negative outcome group（P<0.05）.The D-D levels diagnoses the area under the ROC curve of NRDS as 0.56,and the D-D/FIB ratio diagnoses the area under the ROC curve of NRDS as 0.57.The D-D/FDP ratio was not statistically significant in all groups for early preterm outcomes（P>0.05）.Conclusions1.Plasma D-D levels were significantly elevated in preterm infants of different gestational ages in the early period of life after birth,starting from 28 weeks of gestational age,with the increase of the gestational age at birth,the level if D-dimer decreased gradually.However,it is still significantly higher than the normal adult D-D reference standard（<0.5 mg/L）,and there may be a large error in using the adult standard（D-D level<0.5 mg/L）to determine whether there is an abnormal elevation of D-D in preterm infants in the early period of life after birth.2.Gestational age<32 weeks,umbilical artery blood gas abnormalities,maternal placental abruption,and vaginal delivery are all independent risk factors for significantly elevated plasma D-D levels in the early stages of preterm infants,which may increase the risk of significantly elevated D-D.3.Preterm infants with NRDS within 72 hours of age have higher levels of D-D and lower D-D/FIB ratios within 48 hours after birth.In this study,D-D/FDP ratio may not be valuable for assessing the occurrence of early postnatal outcomes such as early-onset sepsis（EOS）,NRDS,disseminated intravascular coagulation（DIC）,bleeding disorders,and death.