Evaluation of Noninvasive Prenatal Testing (NIPT) guidelines using the AGREE II instrument.

Objective: The rapid increase of cell-free fetal DNA analysis for Down syndrome screening requires evidence-based clinical practice guidelines for noninvasive prenatal testing (NIPT). Several studies show that the quality of many guidelines is low and there are still many health areas where this quality is not systematically evaluated. Given the absence of research, in the NIPT field, we used an internationally validated tool to evaluate a set of three NIPT practice guidelines and to look at dimensions that can be improved.Methods: Four appraisers, experts in prenatal screening, evaluated three main NIPT guidelines published in the last 2 years using the AGREE II (Appraisal of Guidelines for Research and Evaluation II), a tool specifically designed for guideline quality appraisal.Results: Guidelines scored higher in domains related with scope, purpose, and clarity of presentation, and lower in stakeholder involvement and rigor of development. Intradomain items evaluation showed asymmetries between guidelines. The UK-NSC was the guideline with the best scores.Discussion: Several areas of NIPT guidelines, such as stakeholders involvement, selection of supporting evidence, external reviews, updating processes, and competing interests disclosure, can be improved. Appraisers recommend modifications to all NIPT guidelines that can lead to substantial improvements in their methodological quality and subsequently make a contribution to prenatal screening improvement.

Maternal serum alpha-fetoprotein in normal pregnancy at 11-13 weeks' gestation.

OBJECTIVE: To establish a reference distribution of maternal serum alpha-fetoprotein (AFP) at 11-13 weeks' gestation and define the contribution of maternal variables that influence the measured concentration of AFP. METHODS: Serum concentration of AFP at 11-13 weeks was measured in 1,500 singleton pregnancies which were not complicated by hypertensive disorders or diabetes mellitus and resulted in the live birth at or after 37 weeks of phenotypically normal neonates with birth weights above the 5th and below the 95th percentile. Multiple regression analysis was used to account for maternal characteristics that influence the measured concentration of AFP and a distribution of log multiples of the median (MoM) values was fitted. RESULTS: Log(10) AFP increased with gestational age, decreased with maternal weight and was significantly affected by maternal racial origin, smoking status and method of conception. Compared with values in Caucasian women who were non-smokers and conceived spontaneously, AFP MoM was on average 23% higher in Afro-Caribbeans and 8% lower in East Asians, 11% higher in smokers and 10% higher in those conceiving by in vitro fertilization. CONCLUSION: In normal pregnancies at 11-13 weeks, serum AFP increases with gestational age and is affected by maternal race, weight, smoking status and method of conception.