The Role of Technology in Newborn Screening

The Beginnings of Newborn Screening

Screening newborns in the full population for inherited metabolic disorders (IMDs) was the brainchild of Dr. Robert Guthrie, a New England physician and microbiologist with family members afflicted with phenylketonuria (PKU), a defect of phenylalanine metabolism resulting in profound and irreversible intellectual disability if untreated soon after birth. Dr. Guthrie's PKU screening method was based on a simple, inexpensive microbiological test known as the bacterial inhibition assay. It was performed on dried blood spots collected at birthing centers and mailed to the public health laboratory. The test identified at-risk infants based on elevated phenylalanine levels in the dried blood spots [1]. More advanced tests were utilized to ascertain those infants truly affected with PKU, who were promptly treated with a special diet that prevented the onset of intellectual disability. PKU screening began in New England in 1963 and subsequently spread to public health systems in all other states (North Carolina began statewide screening in 1966) and across most of the developed world.

Slow but Steady

The introduction of new dried blood spot tests in the United States for other IMDs required satisfaction of the population screening guidelines established by Wilson and Jungner in 1968 [2]. This required the existence of a suitable screening test, an effective preventive treatment, an early onset form of the disease that would be debilitating if not treated soon after birth, and overall cost-effectiveness, all of which generally took decades to come to fruition. Thus in North Carolina, for example, screening was gradually introduced for congenital hypothyroidism, galactosemia, and congenital adrenal hyperplasia (see Table 1). By the mid-1990s, most newborn screening programs in the United States were still screening for just three to five IMDs, each specific test requiring a separate dried blood spot sample and a laboratory equipped with the means to perform that test. The North Carolina public health laboratory (NCPHL) also began testing for sickle cell disease and sickle trait in 1987, and later expanded the hemoglobinopathy panel to include related conditions, including beta-thalassemia. Although technological improvements needed to screen for most of these conditions were introduced—liquid chromatography replacing the bacterial inhibition assay for PKU, for example—the practice of developing a single test for each IMD screened for was the prevailing paradigm, until the introduction of tandem mass spectrometry (MS/MS) disrupted the status quo.

Digital Microfluidics Makes its Mark

DMF refers to a method for manipulating individual droplets on the surface of a printed circuit board by software control using the principle of electrowetting [13]. One of the major developments of this principle emerged from the Duke University School of Engineering and with the help of government grants collaborated with researchers at Duke University Medical Center to develop assays intended for use at the point of care in the neonatal nursery. Further collaboration with the Duke Biochemical Genetics Laboratory and the North Carolina State Newborn Screening Lab resulted in a method based on microfluorometry to screen newborns for up to five LSDs using the extract from a single dried blood spot sample [14]. Advanced Liquid Logic introduced a practical DMF system to screen for four LSDs that was adopted by the Missouri state newborn screening program in January 2013. This system has operated continuously since then and has successfully tested over 350,000 newborns [15]. The DMF platform known as SEEKER™ received approval from the US Food and Drug Administration (FDA) in 2017. Since the recent addition of Pompe and MPS-1 to the RUSP, most US newborn screening programs have opted to screen for at least these two LSDs, with the choice of method roughly divided between MS/MS and DMF. Although the pros and cons of these methods have been hotly debated in the literature, recent results from Illinois, which uses MS/MS [16], and Missouri, using DMF [15], are quite similar. DMF is now well-established as a new technology in newborn screening and could, in the future, be deployed in birthing centers for conditions that are particularly time-critical, such as galactosemia, congenital hypothyroidism, and SCID, thus avoiding delays in their detection and treatment [17].

New Initiatives in North Carolina

Our state's newborn screening program has always prided itself on being progressive and open-minded with regard to adding conditions to its testing panel and embracing new concepts and technology when appropriate. Without their generosity of spirit and cooperation, it might have taken several decades longer for MS/MS to become an established technology in newborn screening. In order to better position North Carolina's response to new challenges, collaborative efforts between RTI International, based in the Research Triangle Park, the University of North Carolina at Chapel Hill, Duke University, and the North Carolina newborn screening Lab have facilitated pilot studies for MPS 1 and X-ALD. A new research initiative from RTI called “Early Check” [18] secured funding to initiate screening for Fragile X syndrome and spinal muscular atrophy on a research basis in North Carolina in the fall of 2018 (see article by Bailey and Gehtland in this issue [19]). Table 1 summarizes the current list of conditions targeted by newborn screening in North Carolina, with the dates of implementation.

Will New DNA Technology Create Another Revolution in Newborn Screening?

There has been a major revolution in DNA sequencing technology during recent years, and few can doubt its impact on the current and future practice of medicine [20]. DNA tests are already widely utilized in newborn screening, primarily as second-tier methods to improve the diagnostic specificity of primary screening tests, such as cystic fibrosis, for example. The primary newborn screening test for SCID uses a DNA-based assay, albeit for a unique biomarker rather than for identifying gene pathogenic variants [21]. Newborn screening for spinal muscular atrophy requires a targeted DNA test for deletion of exon 7 in the SMN1 gene because there is no suitable biomarker. A new research study to screen for Fragile X syndrome will also depend on novel DNA technology. But the big question remains: Is there a case for whole genome or exome sequencing as a primary newborn screening test for all newborns, rather than for a select group of neonatal intensive care unit (NICU) babies with undiagnosed clinical problems? Many believe so, leading to a sense of inevitability that we might expect to see this occur in at least one newborn screening program, possibly in Europe. Counter-arguments center mostly on cost, ethical/legal issues, and on lack of resources to follow-up on results from the initial testing, many of which will be uncertain or uninterpretable [22] and likely will prevent or delay genome sequencing in the United States. Approximately five years ago, the National Institute of Child Health and Human Development awarded grants worth $25 million to four centers in the United States, including the University of North Carolina, to study various aspects of next-generation DNA testing in newborns. The North Carolina project (NC-NEXUS) includes a research study to explore the utility of next-generation sequencing in newborn screening and parental decision-making [23]. The results of these studies will enable a deeper understanding of the issues surrounding DNA screening in newborns [20]. The most likely use of novel DNA sequencing technology in newborn screening is a comprehensive panel targeting conditions currently on the RUSP. This could provide valuable information, when combined with existing biochemical testing methods, to indicate or refute a potential diagnosis.

In summary, technology is a vital and principal force that moves newborn screening forward (see Figure 1). The North Carolina newborn screening program, through its collaboration with neighboring institutions, has achieved a unique record of success in the promotion and adoption of new technologies, with significant and ongoing benefit to the newborns in North Carolina affected by IMDs.

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FIGURE 1.

Technology Developments in the Newborn Screening Laboratory