Farrell P M, Koscik R E
Department of Pediatrics, University of Wisconsin, Madison, 53792-4108,USA.
Pediatrics. 1996 Apr;97(4):524-8.
To determine whether an adequate volume of sweat could be obtained routinely from infants younger than 6 weeks old and to evaluate sweat chloride levels in infants with known genotype statuses, including heterozygote carriers for cystic fibrosis (CF).
Infants were evaluated using pilocarpine iontophoresis and measurement of sweat volume and chloride concentration. The majority of these infants were referred because of newborn screening test results positive for CF based on immunoreactive trypsinogen analysis. DNA analyses for the 3-base pair deletion at codon 508 of the CF transmembrane regulator gene (F508 mutation) were performed whenever possible, and patients with CF were categorized by genotype.
Sweat tests were performed successfully (>/-50 mg of sweat) in 99.3% of the infants tested, and there was no difference in the proportion of unsuccessful tests in infants younger than or older than 6 weeks of age. The normal mean +/- SD sweat chloride was 10.6 +/- 5.2 mEq/L (95% confidence interval, 9.9-11.3). Patients with CF who are F508 homozygotes or F508 compound heterozygotes or who have two other non-F508 mutant alleles were shown to have similar sweat chloride levels, with mean values of 99.9, 98.8, and 96.6 mEq/L, respectively. The group of infants who were found to be CF (F508) heterozygote carriers, when compared with the healthy group, had mildly but significantly increased sweat chloride concentrations, with a mean +/- SD of 14.9 +/- 8.4 mEq/L (95% confidence interval, 13.4-16.4).
Quantitative pilocarpine iontophoresis can be used successfully in infants younger than 6 weeks of age who are undergoing routine diagnostic evaluations to follow up newborn screening test results that are positive for CF. The upper limit of normal sweat chloride in infants should be revised to 40 mEq/L (mean + 3 SD of the CF heterozygote carrier group). CF heterozygote carrier infants with one F508 mutant allele show phenotypic manifestations of CF, including subclinical elevations of sweat chloride.
确定能否常规从6周龄以下婴儿获取足够量的汗液，并评估已知基因型状态婴儿的汗液氯化物水平，包括囊性纤维化（CF）杂合子携带者。
采用毛果芸香碱离子电渗疗法对婴儿进行评估，并测量汗液量和氯化物浓度。这些婴儿大多数因基于免疫反应性胰蛋白酶原分析的新生儿筛查试验结果CF呈阳性而被转诊。只要有可能，就对CF跨膜调节基因第508密码子处3个碱基对缺失（F508突变）进行DNA分析，并根据基因型对CF患者进行分类。
99.3%接受检测的婴儿汗液试验成功（汗液量≥/ - 50mg），6周龄以下和6周龄以上婴儿试验未成功的比例无差异。正常汗液氯化物平均±标准差为10.6±5.2mEq/L（95%置信区间，9.9 - 11.3）。F508纯合子、F508复合杂合子或有两个其他非F508突变等位基因的CF患者汗液氯化物水平相似，平均值分别为99.9、98.8和96.6mEq/L。与健康组相比，被发现为CF（F508）杂合子携带者的婴儿组汗液氯化物浓度轻度但显著升高，平均±标准差为14.9±8.4mEq/L（95%置信区间，13.4 - 16.4）。
对于因新生儿筛查试验结果CF呈阳性而接受常规诊断评估的6周龄以下婴儿，定量毛果芸香碱离子电渗疗法可成功应用。婴儿正常汗液氯化物上限应修订为40mEq/L（CF杂合子携带者组平均值 + 3标准差）。具有一个F508突变等位基因的CF杂合子携带者婴儿表现出CF的表型特征，包括汗液氯化物亚临床升高。
