Meta Analysis Of The Correlation Between FeNo And Eosinophils In Peripheral Blood And Sputum In Patients With AECOPD

Background and purpose:Chronic obstructive pulmonary disease(COPD)is a common clinical respiratory disease that can be prevented and treated.The main reason for frequent medical visits,hospitalizations and deaths in COPD patients is the acute exacerbation of COPD(AECOPD).Therefore,early detection,diagnosis,and treatment of AECOPD can help slow the progression of the disease.Studies have found that 10%-40%of patients with AECOPD exhibit eosinophilic inflammation,and the rise in eosinophils also increases the risk of AECOPD.Fractional exhaled nitric oxide(FeNo)is a non-invasive,non-invasive test that can quickly,safely and easily detect eosinophilic inflammatory responses in the airways.The FeNo test has been widely used in asthma,although its use in patients with COPD has not been clearly defined.Although its application in patients with COPD has not been clearly established,with the increasing number of studies on the application of FeNo in COPD and AECOPD,the role of FeNo is becoming more and more widespread.However,some studies have also found no significant correlation between eosinophil and FeNo levels in AECOPD patients.Based on this,we conducted a meta-analysis of clinical trials that studied the level of eosinophils and FeNo levels in sputum or peripheral blood of AECOPD patients.The purpose of this Meta-analysis was to investigate whether FeNo levels and eosinophils in patients with AECOPD are correlated,and to determine whether FeNo testing has clinical significance in predicting the occurrence and severity of AECOPD.Method:By computer search databases Embase,Pub Med,Cochrane Library,Google Scholar,China,CNKI,CBM.The search subject terms are" Pulmonary Disease,Chronic Obstructive","Pulmonary Disease,Chronic Obstructive",and "Eosinophils" and "Eosinophils",and the free terms "Chronic Obstructive Lung Disease","Chronic Obstructive","Pulmonary Diseases","COPD","COAD","Chronic Obstructive Airway Disease","Chronic Obstructive Pulmonary Disease","Airflow Obstruction,Chronic","Airflow Obstructions Chronic","Chronic Airflow Obstructions","Chronic Airflow Obstruction","AECOPD","Exhaled Nitric Oxide Test","FeNo Test","FeNO","Fractional Exhaled Nitric Oxide".The main inscription and free words were linked by logical relation words and truncated words.The search was conducted from the date of database creation to April 30,2022,and relevant references were searched and screened to prevent omission.The literature was screened independently by two investigators according to the established inclusion and exclusion criteria,while quality evaluation was performed.The cross-sectional studies were evaluated using the AHRQ evaluation criteria,and the case-control studies were evaluated using the NOS evaluation criteria.Differences were discussed and resolved,and expert opinions were sought if necessary.The data included in the study were processed and analyzed by RevMan5.4 software,and the heterogeneity tests were performed at the same time.Results:A total of 614 articles were retrieved,by excluding duplicate literature,title and screening,and full-text reading screening,10 papers were finally included in this study,that included 9 cross-sectional studies and 1 case-control study,and all of which were of medium to high quality.A total of 1319 samples were included,including the experimental group(eosinophil hypertrophy group,n=490)and the control group(non-eosinophilia group,n=829).Through Meta analysis,it was found that:(1)The Eosinophil elevated group had higher FeNo levels than the control group,and eosinophil levels were positively correlated with FeNo levels(MD 14.76[95%Cl 7.77-21.74];P<0.0001).The results were highly heterogeneous,so a random-effects model was used.Sensitivity analysis andSubgroup analysis revealed that the sputum eosinophil elevation group had a higher FeNo level than the peripheral blood eosinophil elevation group level(MD 15.51[95%Cl 10.26-20.39];I2=0%;P<0.00001).In addition,the eosinophil-elevated non-hormonal treatment group showed a greater decrease in FeNo than the non-eosinophil-elevated non-hormonal treatment group(MD 3.62[95%CI 0.15-7.10];P=0.04),however,FeNo levels decreased more in the eosinophil-elevating hormone-treated group than in the non-eosinophil-elevating hormone-treated group(MD treatment group(MD 18.33[95%CI 5.80-30.87];P=0.004),all with statistically significant differences.(2)The group with elevated eosinophils in AECOPD patients had higher FEV1/FVC(MD 0.88[95%CI-0.22-1.97];P=0.12;I2=0%)and FEV1pred%(MD 1.36[95%CI-0.59-3.32];P=0.17;I2=48%)levels,but the results were not statistically significant.The eosinophil-elevated group had higher FEV1 than the non-eosinophil-elevated group(MD 0.12[95%CI 0.00-0.24];P=0.05;I2=77%)than the non-eosinophil elevated group,with greater heterogeneity.After sensitivity analysis,it was found that the heterogeneity of Meta analysis was significantly decreased after excluding a literature(MD 0.08[95%CI 0.01-0.14];P=0.03;I2=1%),and the results were statistically significant.Meanwhile,the test group had higher levels of FVC(MD 0.35[95%CI 0.10-0.59];P=0.005;I2=90%),the difference was statistically significant and the results were heterogeneous,using a random effects model.(3)The eosinophil level in AECOPD patients was negatively correlated with white blood cell count(WBC)(MD-0.97[95%CI-1.64--0.30];P=0.004;I2=0%)and C-reactive protein(CRP)(MD-0.32[95%CI-0.58--0.06];P=0.01;I2=32%),the difference is statistically significant,the heterogeneity is small,and the fixed effect model is used.(4)The total hospital days in AECOPD patients with elevated eosinophils were shorter than thatin the control group(MD-2.49[95%CI-3.44-1.53];P<0.00001;I2=75%),with a statistically significant difference and a large heterogeneity.TThe heterogeneity of the results was significantly lower after excluding one article(MD-2.93[95%CI-3.35--2.52];P<0.00001;I2=0%),the difference has a statistical meaning,using a fixed effect model.(5)CAT scores in the experimental group were slightly but not significantly different from those in the control group(MD 0.33[95%CI-0.33-0.94];P=0.29;I2=33%).Conclusions:1.Patients with AECOPD had higher FeNo levels in the sputum and peripheral blood eosinophil elevation groups,which were positively correlated,with the sputum eosinophil elevation group having higher FeNo levels than the peripheral blood eosinophil elevation group.2.FeNo values may be used to predict the efficacy of hormone therapy in patients with AECOPD.3.Eosinophil count was positively correlated with FEV1/FVC,FEV1pred%,FEV1 and FVC levels in patients with AECOPD.4.Peripheral blood WBC count and CRP levels were lower in the group with elevated eosinophils in AECOPD patients.5.Total hospital days were shorter in the group with elevated eosinophils in AECOPD patients.