Although they usually can’t be seen in newborns, metabolic birth defects can cause a variety of physical problems, mental retardation, and even death.

Screening newborns for metabolic disorders began in the 1960s, with a screening test for phenylketonuria, a condition that can lead to mental retardation if left untreated. Over the years, separate screening tests for other metabolic disorders were developed. More recently, researchers have developed tandem mass spectrometry, which is capable of screening for multiple disorders with one sample of blood. The table below lists the most commonly screened disorders:

Phenylketonuria (PKU)An inability to process phenylalanine (a protein component), which can lead to brain damage and mental retardation.
Hypothyroidism A hormone deficiency that slows growth and development.
Galactosemia An inability to process galactose (a milk sugar), which can cause infant death, blindness, or mental retardation
Sickle Cell Anemia A blood disease that causes pain, damage to vital organs, and sometimes death.
Congenital adrenal hyperplasia (CAH)A hormone deficiency that affects genital development, and can disturb kidney function and cause death

In the U.S., all states screen for certain metabolic birth defects, but, to date, only 24 states mandate that tandem mass spectrometry be offered to all parents of newborns. Some states have been reluctant to adopt tandem mass spectometry because questions about its accuracy and effectiveness still remain unanswered. Do children whose disorder is identified through screening have better health outcomes than children whose disorders are identified later, in a clinical setting? Are the families of children who screen positive for a disorder, but don’t really have it (a false-positive result) placed under an excessive amount of stress?

A new study in the November 19, 2003 issue of the Journal of the American Medical Association found that children whose metabolic disorders were identified by newborn screening had significantly better health outcomes than children who were identified in a clinical setting. The researchers also found that the mothers—but not fathers—of children who had false-positive screening results reported significantly higher levels of stress.

About the Study

This study included four groups of participants:

  • Screened group - Families of 50 children with metabolic disorders that were detected through tandem mass spectrometry
  • Clinically identified group - Families of 33 children with metabolic disorders that were identified later on in a clinical setting
  • False-positive group - Families of 94 children who had false-positive screening results
  • Comparison group - Families of 81 children who had normal screening results

The children with metabolic disorders were medically examined and tested for cognitive development. In addition, the researchers interviewed all of the parents in the study (254 mothers and 153 fathers) to assess parental stress.

The researchers used these data to make the following comparisons:

  • The health outcomes of screened versus clinically identified children
  • The amount of stress placed on screened versus clinically identified families
  • The amount of stress placed on false-positive versus comparison families

The Findings

The children in the screened group, who were treated an average of four months sooner than those in the clinically identified group, had significantly better health outcomes. Specifically, during the first six months of their life, 55% of the children in the clinically identified group required hospitalization at least once, compared with 28% of the children in the screened group. The children in the screened group were significantly less likely to experience complications after diagnosis, or require additional medical interventions or services.

Children in the screened group scored significantly higher on all tests of developmental status. Children in the clinically identified group were more likely to function in the range of mental retardation, and exhibit deficits in communication, daily living skills, socialization, and motor skills.

Mothers—but not fathers—in the screened group reported less overall stress, especially those who reported a better understanding of newborn screening.

Significantly more children in the false-positive group versus the comparison group were hospitalized. The mothers—but not fathers—in the false-positive group reported more stress. Referral to a metabolic center after the initial positive result and notification of repeat screening results helped decrease this stress.

These findings are interesting, but have certain limitations. First, the children in the screened group were significantly younger at both diagnosis and evaluation than the children in the clinically identified group. This may have affected the results. Also, it is possible that newborn screening detects mild abnormalities that would never produce clinical symptoms, which may be part of the reason children in the screened group had better outcomes than children in the clinically identified group.

How Does This Affect You?

These findings provide arguments both for and against the widespread adoption of tandem mass spectometry. While the children in the screened group had better health outcomes, false-positive screening results have adverse consequences. And since false-positive results accounted for over 90% of all positive screening results in the region analyzed in this study, these consequences—increased maternal stress and rate of hospitalization—are no small matter.

Tandem mass spectrometry only detects an estimated 12 disorders per 100,000 births. Would another health program for newborns be more effective? That’s a hard question to answer. Families of children affected by one of these disorders would benefit greatly—by better health outcomes for the child and less stress for the family. On the other hand, mandating tandem mass spectrometry is expensive (with estimated start-up costs of $400,000 per state), and a program that could potentially benefit more children may be a better use of funds.

This study highlighted the importance of parent education on newborn screening. According to the March of Dimes, there are some things you should know before your newborn is screened. First, don’t be overly alarmed if test results come back abnormal; there is a high rate of false-positive results with tandem mass spectrometry. Also, keep in mind that if your baby does have a birth defect, early diagnosis and treatment can often make the difference between lifelong disabilities and healthy development.