A metabolic disorder that can lead to developmental delay and other problems is more common than previously assumed, but does not meet major criteria for inclusion in newborn screening programs at this time, according to a study in the August 23/30 issue of JAMA.
Short-chain acyl-coenzyme A dehydrogenase deficiency (SCADD) is a condition in which the body cannot oxidize fatty acids because an enzyme is either missing or not functioning correctly. The clinical signs and symptoms of SCADD include developmental delay, hypoglycemia (low blood sugar levels), and epilepsy, according to background information in the article. It is an autosomal recessive disorder, which means the gene defect for SCADD only emerges when it is passed on to a child from both parents who carry the faulty gene. Screening for SCADD is included in expanded newborn screening programs in most U.S. and Australian states.
Bianca T. van Maldegem, M.D., of the University of Amsterdam, the Netherlands, and colleagues conducted a retrospective study involving 31 Dutch SCADD patients diagnosed between January 1987 and January 2006, and eight SCADD relatives. The focus of the study was to describe the genetic, biochemical, and clinical characteristics of SCADD patients and their relatives, and to explore the relation of genotype (the genetic constitution) to phenotype (the expressed features).
The researchers calculated a birth-prevalence of at least 1:50,000. "Most patients presented before the age of three years, with non-specific, generally uncomplicated, and often transient symptoms," they write. "Developmental delay, epilepsy, behavioral disturbances, and hypoglycemia were the most frequently reported symptoms."
The study did not reveal an association between the genotype and the clinical features in SCADD.
"Because SCADD does not meet major newborn screening criteria, it is not suited for inclusion in newborn screening programs at this time," the authors conclude.
(JAMA. 2006;296:943-952. Available pre-embargo to the media at www.jamamedia.org.)
Editor's Note: This work was supported by a research grant to Dr. van Maldegem and co-author Frits A. Wijburg, M.D., Ph.D., from the "Metabole Fonds" of the Academic Medical Center, Amsterdam. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.
Editorial: Newborn Screening for Metabolic Disorders
In an accompanying editorial, Susan E. Waisbren, Ph.D., of Children's Hospital Boston, writes that the study by van Maldegem and colleagues provides useful information on this issue, but their data do not provide enough information to rationalize the exclusion of SCADD from screening panels.
"Long-term studies comparing children identified by newborn screening with clinically identified children are needed," she writes. "In addition to laboratory and genetic tests, long-term follow-up studies should include objective measures of outcome, such as growth, nutritional status, physical well-being, number of hospitalizations, number of emergency department visits, intelligence quotient levels, academic achievement, behavioral characteristics, language development, and motor skills."
"Only through comprehensive, long-term research will a rational, fair, and universal newborn screening policy become reality," she concludes.
(JAMA. 2006;296:993-995. Available pre-embargo to the media at www.jamamedia.org.)
Editor's Note: Dr. Waisbren receives grant support from the U.S. Department of Health and Human Services, Health Resources and Services Administration, Maternal and Child Health Bureau. Dr. Waisbren's research on parental response and child outcomes in newborn screening is supported by the National Institutes of Health, Human Genome Project, Division of Ethical, Legal, and Social Implications.