Programa de Pós-graduação em Medicina e Saúde, Universidade Federal da Bahia, Salvador, Brasil.
Escola Bahiana de Medicina e Saúde Pública, Salvador, Brasil.
Cad Saude Publica. 2024 Aug 26;40(7):e00150623. doi: 10.1590/0102-311XEN150623. eCollection 2024.
The Brazilian Unified National Health System (SUS) has incorporated newborn screening for cystic fibrosis since 2001. The protocol involves two samples of immunoreactive trypsinogen (IRT1/IRT2). This study aims to analyze fixed and floating values at the first and second IRT (IRT1/IRT2) cutoff points and assess the accuracy of the IRT/IRT methodology in a population from Northeastern Brazil. Descriptive, individual-level data from the newborn screening reference service data system (2013-2017) were used in this observational population study. The sensitivity, specificity, and positive predictive values (PPV) for the protocol were calculated. The best cutoff point was determined using the Youden's index. The previous year's cut-off values for the IRT1 and IRT2 99.4-, 99.5-, 99.6-, and 99.7-percentiles were utilized for the floating cutoff. During the studied period, 840,832 newborns underwent screening for cystic fibrosis, obtaining 49 cystic fibrosis diagnoses: 39 by newborn screening (79.6%) and 10 (20.4%) by clinical suspicion (false negative). The sensitivity, specificity, and PPV of the protocol totaled 79.6%, 99.9%, and 6.1%, respectively. No proposed cutoff for IRT1 performed better than the current one. IRT2 performed similarly to the current protocol at a cutoff point of 90ng/mL, showing the appropriate sensitivity and specificity while reducing the frequency of false positives. The protocol to screen newborns for cystic fibrosis had low sensitivity, a predictive positive value, and a high number of false positives and negatives. A floating cut point for IRT1 or IRT2 seems to constitute no viable option. However, changing the IRT2 cut point from 70ng/mL to 90ng/mL seems to have advantages and should undergo consideration.
巴西统一的国家卫生系统（SUS）自 2001 年起将囊性纤维化的新生儿筛查纳入其中。该方案涉及两份免疫反应性胰蛋白酶原（IRT1/IRT2）样本。本研究旨在分析第一次和第二次 IRT（IRT1/IRT2）截止点的固定和浮动值，并评估 IRT/IRT 方法在巴西东北部人群中的准确性。本观察性人群研究使用了新生儿筛查参考服务数据系统（2013-2017 年）的描述性个体水平数据。计算了该方案的敏感性、特异性和阳性预测值（PPV）。使用 Youden 指数确定最佳截止点。IRT1 和 IRT2 的前一年 99.4%、99.5%、99.6%和 99.7%百分位数的浮动截止值用于浮动截止。在所研究期间，对 840832 名新生儿进行了囊性纤维化筛查，共发现 49 例囊性纤维化诊断：39 例通过新生儿筛查（79.6%）和 10 例（20.4%）通过临床怀疑（假阴性）。该方案的敏感性、特异性和 PPV 分别为 79.6%、99.9%和 6.1%。没有提出的 IRT1 截止值比目前的截止值表现更好。当 IRT2 的截止值为 90ng/mL 时，与现行方案相似，具有适当的敏感性和特异性，同时减少了假阳性的频率。用于筛查新生儿囊性纤维化的方案敏感性、阳性预测值和假阳性和假阴性率均较低。IRT1 或 IRT2 的浮动截止点似乎不是可行的选择。然而，将 IRT2 的截止值从 70ng/mL 更改为 90ng/mL 似乎具有优势，应该进行考虑。
