Friedrich W, Schmalisch G, von Klinggräff A, Fliegner S, Eckert U, Wauer R R
Frauenklinik, Universitätsklinikum Charité, Humboldt-Universität.
Klin Padiatr. 1996 Mar-Apr;208(2):61-7. doi: 10.1055/s-2008-1043996.
The surface tension value (gamma min) of tracheal aspirate samples (TA) from newborns depends on lung maturity and is determined by concentrations of surfactant components (phospholipids, surfactant proteins, ions). During tracheal aspirate collecting the aspirate is diluted with physiological saline. Information about TA dilution is necessary for a standardized surface tension measurement. The purpose of this study was to establish an ELISA for determination of secretory IgA (SIgA), to determine the cutoff value of SIgA for surface tension measurement in tracheal aspirates and to test SIgA as marker for tracheal aspirate dilution.
In group 1 (normal range determination of gamma min) pharyngeal aspirates of 42 healthy newborns (nb) were investigated. In group 2 (determination of SIgA cutoff value) 15 TA and 8 pharyngeal aspirates of 23 pulmonary healthy nb (group 3) were used for validation of SIgA cutoff value. In group 4 36 TA of 22 nb with respiratory distress syndrome were studied.
The gamma min of group 1 were measured to establish the range of normal gamma min. The TA of group 2 were diluted stepwise and the dependence of gamma min on SIgA concentration were depicted in a diagram. The SIgA cutoff value was estimated by these dilution curves. Below this value the TA are very diluted and a measurement of gamma min is not useful. To test the reliability of SIgA as dilution marker the gamma min and SIgA values of TA from group 3 were determined. After exclusion of TA with reduced SIgA the gamma min of group 3 and 4 were compared.
For the enzyme immunoassay following performance characteristics were determined: the accuracy (recovery): 95.6%, sensitivity: 4 ng/ml, and precision (intra- and interassay coefficient of variation): 9.8 and 19.1%, respectively. The range of normal gamma min (median (5th and 95th percentile)) amounts to 23.0 (14.8 and 28.7) mN/m. A SIgA cutoff value of 80 ng/ml was estimated. The gamma min from 8 of 27 TA (group 3) were above the normal range of gamma min during examination of the estimated SIgA cutoff value. 5 of these 8 TA had concentrations of SIgA below the cutoff point and could be excluded with the help of SIgA as dilution marker. The median of gamma min was significantly lower (p < 0.001) in group 3 (18.3 mN/m) in comparison to the median (35.8 mN/m) of group 4 (nb with respiratory distress syndrome).
The performance characteristics of the SIgA enzyme immunoassay and the tested reliability of the SIgA cutoff value demonstrate, that a simple determination of surfactant deficiency by surface tension measurement of TA is possible using the concentration of SIgA as dilution marker.
新生儿气管吸出物样本（TA）的表面张力值（γmin）取决于肺成熟度，并由表面活性剂成分（磷脂、表面活性剂蛋白、离子）的浓度决定。在收集气管吸出物时，吸出物用生理盐水稀释。关于TA稀释的信息对于标准化表面张力测量是必要的。本研究的目的是建立一种用于测定分泌型IgA（SIgA）的酶联免疫吸附测定法（ELISA），确定气管吸出物表面张力测量中SIgA的临界值，并测试SIgA作为气管吸出物稀释标志物的情况。
在第1组（γmin正常范围测定）中，对42例健康新生儿的咽吸出物进行了研究。在第2组（SIgA临界值测定）中，使用23例肺部健康新生儿（第3组）的15份TA和8份咽吸出物来验证SIgA临界值。在第4组中，研究了22例患有呼吸窘迫综合征的新生儿的36份TA。
测量第1组的γmin以确定正常γmin范围。第2组的TA逐步稀释，并在图表中描绘γmin对SIgA浓度的依赖性。通过这些稀释曲线估计SIgA临界值。低于该值时，TA被过度稀释，γmin的测量没有意义。为了测试SIgA作为稀释标志物的可靠性，测定了第3组TA的γmin和SIgA值。在排除SIgA降低的TA后，比较了第3组和第4组的γmin。
对于酶免疫测定法，确定了以下性能特征：准确度（回收率）：95.6%，灵敏度：4 ng/ml，精密度（批内和批间变异系数）：分别为9.8%和19.1%。正常γmin范围（中位数（第5和第95百分位数））为23.0（14.8和28.7）mN/m。估计SIgA临界值为80 ng/ml。在评估估计的SIgA临界值时，27份TA（第3组）中的8份TA的γmin高于γmin正常范围。这8份TA中有5份SIgA浓度低于临界值，借助SIgA作为稀释标志物可将其排除。与第4组（患有呼吸窘迫综合征的新生儿）的中位数（35.8 mN/m）相比，第3组的γmin中位数显著更低（p < 0.001）（18.3 mN/m）。
SIgA酶免疫测定法的性能特征以及SIgA临界值的测试可靠性表明，使用SIgA浓度作为稀释标志物，通过测量TA的表面张力来简单测定表面活性剂缺乏是可行的。
