Research On The Distribution Of Respiratory Pathogens And Levels Of SAA And CRP In Children Aged 0-6 Years Old With Acute Respiratory Infections In Lanzhou

Objective:By detecting respiratory pathogens in children with acute respiratory infections（ARI）,simultaneously detecting changes in the levels of serum amyloid A（SAA）and C-reactive protein（CRP）,and analyzing the effects of air quality on children respiratory infections,this study explored the correlation between respiratory pathogens,SAA,CRP,age,and air quality index（AQI）,and provided theoretical basis for the early diagnosis of ARI in children.Methods:This study used a retrospective analysis to include 539 childre n with ARI who received treatment at the Gansu Provincial Maternal and Chil d Health Hospital between September 2020 and August 2022.All patients had at least one respiratory pathogen IgM antibody positive.At the same time,we also included 556 serum specimens from respiratory pathogen IgM antibody-negative children who were treated in the hospital during the same period as t he control group.The nine respiratory pathogens IgM antibodies were detecte d using a magnetic particle chemiluminescence assay（CLIA）.Serum CRP and CAA levels were measured using immunoturbidimetry.PM_2.5concentration d ata were obtained from the National Urban Air Quality Report released by the China Environmental Monitoring Station.The diagnostic value of serum CRP and SAA levels in children with positive respiratory pathogens was analyzed using receiver operating characteristic（ROC）curve.Results:Among all children with ARI,those aged 13 to 37 months were significantly more than those aged 0 to 6 months and 7 to 12 months（p<0.001）.Among all children with positive IgM antibodies for the nine respiratory pathogens,the proportion of children positive for Mycoplasma pneumoniae（MP）was the highest（63.08%）,followed by Influenza B virus（VIB）（18.00%）,and the proportion of children positive for Chlamydia pneumoniae（CP）was the lowest（0.37%）.The serum CRP levels of children in the Influenza A virus（VIA）-positive group were significantly higher than those of children in the other 7 groups except for the CP-positive group（P<0.05）.In addition,the serum SAA levels of children in the MP-positive group and the Echovirus（ECHO）-positive group were significantly higher than those in the Coxsackie virus（CVB）-positive group（P<0.05）.Spearman analysis shows a positive correlation between serum SAA and CRP levels in children with ARI.At the same time,levels of SAA and IgM antibodies for VIA,adenovirus（ADV）,MP,CP,and human respiratory syncytial virus（RSV）positivity,as well as PM_2.5concentration,showed a positive correlation.Serum SAA diagnosis of positive respiratory pathogens in children with ARI has an area under curve（AUC）of 0.750 under the ROC,with a 95%confidence interval（95%CI）of 0.721-0.779.The AUC significance is less than 0.001,and the cut-off value is 15.86 mg/L.The sensitivity is 70.1%,and the specificity is 69.6%.The ROC curve of CRP combined with SAA in the diagnosis of respiratory pathogens in children with ARI is positive,with an area under the curve of 0.744,a 95%CI of 0.714-0.773,an AUC specificity of less than 0.001,a sensitivity of 74.0%,and a specificity of 66.2%.Conclusion:the main pathogen causing ARI in children aged 0-6 years old is Mycoplasma pneumoniae in Lanzhou area.The level of serum SAA in children with positive Mycoplasma pneumoniae and positive Enterovirus groups is significantly higher than that in children with positive Coxsackie B virus.The serum SAA level has a certain predictive value for respiratory pathogen positivity in ARI patients and is positively correlated with the patient’s serum CRP,PM_2.5,and respiratory pathogen IgM antibody levels.