哮喘儿童呼出气一氧化氮离线式测定方法的适用性研究

Applicability of offline determination of fractional exhaled nitric oxide in children with asthma

目的通过实验室及现场应用实验,验证哮喘儿童呼出气一氧化氮(fractional exhaled nitric oxide,FeNO)离线式测定方法的适用性。方法采用聚对苯二甲酸乙二醇酯(Mylar)采气袋,以50 ml/s流量采集哮喘儿童呼出气样品,采用电化学方法测定一氧化氮(NO)浓度。在实验室中确认方法检出限、精密度、准确度、样品保存时间等特性指标后,应用于62名哮喘儿童的测定,以评价方法的适用性。结果方法检出限为3.3μg/m^3,对FeNO浓度不同的哮喘儿童重复测定6次的相对标准偏差(RSD)为4.2%~9.5%,RSD随测定浓度的升高而降低;不同浓度标准气的测定值与理论值相对偏差(RD)为2.9%~8.7%。在方法比对实验中,本方法与传统的在线式方法测定结果间具有良好的线性正相关关系(r=0.990,P<0.01),且差异无统计学意义(P=0.236)。在室温下(20~25℃)用于FeNO检测的呼出气样品至少可以保存12 h。对62名5~14岁哮喘儿童FeNO现场测定的成功率为98.4%(61/62),成功测定的61名哮喘儿童FeNO平均水平为(22.0±16.2)μg/m^3,中位数为16.9μg/m^3,范围为6.5~83.2μg/m^3;同一调查对象3次测定结果的变异系数(CV)均值为(7.1±4.6)%;FeNO第1次测定结果与3次测定结果的均值间具有良好的线性关系(r=0.997,P<0.01),且二者差异无统计学意义(P=0.141);环境空气中NO浓度对FeNO测定结果无干扰。结论哮喘儿童FeNO的离线式测定方法具有良好的精密度、准确性及较高的测定成功率,且与在线式测定方法结果间具有良好的一致性,可以满足大规模流行病学调查的需要。

Objective To study the applicability of offline determination of fractional exhaled nitric oxide（FeNO） in children with asthma. Methods The exhaled breath was collected into Mylar bag at flow rate of 50 ml/s and then the concentrations of nitric oxide（NO） were determined by electrochemical sensor device. The characteristics of the offline method including detection limit, precision and accuracy, as well as sample storage time were approved in the laboratory test. And then the FeNO of 62 children with asthma were investigated by the offline method for field validation. Results The detection limit of this method was 3.3 μg/m^3, the precisions（relative standard deviation, RSD） were 4.2%-9.5%, and the relative deviations between theoretical values and detection values were 2.9%-8.7% in determination for different levels of NO standard gas. In the method comparison experiment, FeNO values measured with this method were in good agreement with those obtained by traditional online method（r =0.990, P〈0.01）. The NO concentrations in Mylar bag could maintain stable for at least 12 hours at room temperature（20-25 ℃）. In the field study, the success determination rate was 98.4% and average FeNO concentrations from 61 children with asthma successfully measured were（22.0±16.2）μg/m^3（median： 16.9 μg/m^3; range：6.5-83.2 μg/m^3）. The mean coefficients of variation（CV） for triplicate measurements were（7.1±4.6）%. There was also a very strong correlation between the FeNO concentrations from the first measurement and mean concentrations of triplicate measurements（r =0.997, P〈0.01）. The FeNO concentrations were not influenced by NO levels in the environmental air. Conclusion The offline method used in this study is reliable, reproducible and applicable to the large-scale epidemiological investigation.