Sermet-Gaudelus Isabelle, Roussel Delphine, Bui Stéphanie, Deneuville Eric, Huet Frédéric, Reix Philippe, Bellon Gabriel, Lenoir Gérard, Edelman Aleksander
Service de Pédiatrie Générale and CRCM, Hôpital Necker-Enfants Malades, 149 rue de Sèvres, 75743, Paris, France.
BMC Pediatr. 2006 Oct 3;6:25. doi: 10.1186/1471-2431-6-25.
Cystic fibrosis (CF) is caused by mutations in the gene encoding for the CF transmembrane conductance regulator (CFTR) protein, which acts as a chloride channel after activation by cyclic AMP (cAMP). Newborn screening programs for CF usually consist of an immunoreactive trypsinogen (IRT) assay, followed when IRT is elevated by testing for a panel of CF-causing mutations. Some children, however, may have persistent hypertrypsinogenemia, only one or no identified CFTR gene mutation, and sweat chloride concentrations close to normal values. In vivo demonstration of abnormal CFTR protein function would be an important diagnostic aid in this situation. Measurements of transepithelial nasal potential differences (NPD) in adults accurately characterize CFTR-related ion transport. The aim of the present study is to establish reference values for NPD measurements for healthy children and those with CF aged 3 months to 3 years, the age range of most difficult-to-diagnose patients with suspected CF. The ultimate goal of our study is to validate NPD testing as a diagnostic tool for children with borderline results in neonatal screening.
METHODS/DESIGN: We adapted the standard NPD protocol for young children, designed a special catheter for them, used a slower perfusion rate, and shortened the protocol to include only measurement of basal PD, transepithelial sodium (Na+) transport in response to the Na+ channel inhibitor amiloride, and CFTR-mediated chloride (Cl-) secretion in response to isoproterenol, a beta-agonist in a Cl- free solution. The study will include 20 children with CF and 20 healthy control children. CF children will be included only if they carry 2 CF-causing mutations in the CFTR gene or have sweat chloride concentrations > 60 mEq/L or both. The healthy children will be recruited among the siblings of the CF patients, after verification that they do not carry the familial mutation.
A preliminary study of 3 adult control subjects and 4 children older than 12 years with CF verified that the new protocol was well tolerated and produced NPD measurements that did not differ significantly from those obtained with the standard protocol. This preliminary study will provide a basis for interpreting NPD measurements in patients with suspected CF after neonatal screening. Earlier definitive diagnosis should alleviate parental distress and allow earlier therapeutic intervention and genetic counseling.
囊性纤维化（CF）由编码CF跨膜传导调节因子（CFTR）蛋白的基因突变引起，该蛋白在被环磷酸腺苷（cAMP）激活后作为氯离子通道发挥作用。CF新生儿筛查项目通常包括免疫反应性胰蛋白酶原（IRT）检测，当IRT升高时，接着检测一系列导致CF的突变。然而，一些儿童可能存在持续性高胰蛋白酶原血症，仅发现一个或未发现CFTR基因突变，且汗液氯化物浓度接近正常值。在这种情况下，体内CFTR蛋白功能异常的证明将是一项重要的诊断辅助手段。在成人中测量经上皮鼻电位差（NPD）可准确表征与CFTR相关的离子转运。本研究的目的是为3个月至3岁的健康儿童和CF儿童建立NPD测量的参考值，这一年龄段是疑似CF最难诊断的患者群体。我们研究的最终目标是验证NPD检测作为新生儿筛查中结果临界儿童的诊断工具。
方法/设计：我们对幼儿的标准NPD方案进行了调整，为他们设计了一种特殊导管，采用较慢的灌注速率，并缩短方案，仅包括基础电位差测量、对钠离子通道抑制剂氨氯吡咪的经上皮钠（Na+）转运测量以及在无氯溶液中对β受体激动剂异丙肾上腺素的CFTR介导的氯（Cl-）分泌测量。该研究将包括20名CF儿童和20名健康对照儿童。仅当CF儿童在CFTR基因中携带2个导致CF的突变或汗液氯化物浓度>60 mEq/L或两者皆有时才纳入。在确认健康儿童不携带家族性突变后，将从CF患者的兄弟姐妹中招募。
对3名成年对照受试者和4名12岁以上CF儿童的初步研究证实，新方案耐受性良好，所产生的NPD测量值与标准方案获得的值无显著差异。这项初步研究将为解释新生儿筛查后疑似CF患者的NPD测量提供依据。更早的确切诊断应能减轻家长的痛苦，并允许更早的治疗干预和遗传咨询。
