U.S. Preventive Services Task Force

Screening for Phenylketonuria: Reaffirmation Recommendation Statement



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Summary of Recommendation

The U.S. Preventive Services Task Force (USPSTF) recommends screening for phenylketonuria (PKU) in newborns (Table 1). A recommendation.

Table 1

Screening for PKU: Clinical Summary of the USPSTF Recommendation

Population

All newborns

Recommendation

Screen for PKU in newborns

Grade: A

Screening tests

Screening for PKU is mandated in all 50 states. Methods of screening vary.

Three main methods are used to screen for PKU in the United States:

• Guthrie bacterial inhibition assay

• Automated fluorometric assay

• Tandem mass spectrometry

Timing of screening

Infants who are tested within the first 24 hours after birth should receive a repeat screening test by two weeks of age.

Optimal timing of screening for premature infants and infants with illnesses is at or near seven days of age, but in all cases before discharge from the newborn nursery.

Treatment

It is essential that phenylalanine restrictions be instituted shortly after birth to prevent the neurodevelopmental effects of PKU.

Other relevant recommendations from the USPSTF

Additional USPSTF recommendations regarding screening tests for newborns can be accessed at http://www.ahrq.gov/clinic/cps3dix.htm#pediatric.


note: For the full USPSTF recommendation statement and supporting documents, visit http://www.uspreventiveservicestaskforce.org/recommendations.htm.

PKU = phenylketonuria, USPSTF = U.S. Preventive Services Task Force.

Table 1   Screening for PKU: Clinical Summary of the USPSTF Recommendation

View Table

Table 1

Screening for PKU: Clinical Summary of the USPSTF Recommendation

Population

All newborns

Recommendation

Screen for PKU in newborns

Grade: A

Screening tests

Screening for PKU is mandated in all 50 states. Methods of screening vary.

Three main methods are used to screen for PKU in the United States:

• Guthrie bacterial inhibition assay

• Automated fluorometric assay

• Tandem mass spectrometry

Timing of screening

Infants who are tested within the first 24 hours after birth should receive a repeat screening test by two weeks of age.

Optimal timing of screening for premature infants and infants with illnesses is at or near seven days of age, but in all cases before discharge from the newborn nursery.

Treatment

It is essential that phenylalanine restrictions be instituted shortly after birth to prevent the neurodevelopmental effects of PKU.

Other relevant recommendations from the USPSTF

Additional USPSTF recommendations regarding screening tests for newborns can be accessed at http://www.ahrq.gov/clinic/cps3dix.htm#pediatric.


note: For the full USPSTF recommendation statement and supporting documents, visit http://www.uspreventiveservicestaskforce.org/recommendations.htm.

PKU = phenylketonuria, USPSTF = U.S. Preventive Services Task Force.

Rationale

Importance. PKU is an inborn error of phenylalanine metabolism that occurs in 1 in 13,500 to 1 in 19,000 newborns in the United States. In the absence of treatment during infancy, most persons with this disorder will develop severe mental retardation.1,2

Detection. Two approaches, fluorometry and tandem mass spectrometry, are commonly used. The sensitivity and specificity of fluorometry are 100 and 51 percent, respectively.3 The sensitivity and specificity of tandem mass spectrometry are 100 and 98 percent, respectively.3

Benefits of detection and early intervention. There is good evidence that detection by neonatal screening and early treatment of PKU substantially improve neurodevelopmental outcomes for affected persons.

Harms of detection and early treatment. False-positive tests could generate considerable parental anxiety.

USPSTF assessment. The USPSTF concludes that there is high certainty that the net benefit is substantial for screening for PKU in newborns.

Clinical Considerations

  • Patient population. This recommendation applies to newborns.

  • Screening tests. Screening for PKU is mandated in all 50 states, although methods of screening vary. There are three principal methods used for PKU screening in the United States: the Guthrie bacterial inhibition assay, automated fluorometric assay, and tandem mass spectrometry. Screening tests are most accurate if performed after 24 hours of life but before seven days of age.

  • Treatment. It is essential that phenylalanine restrictions be instituted shortly after birth to prevent the neurodevelopmental effects of PKU.

  • Timing of screening. Infants who are tested within the first 24 hours after birth should receive a repeat screening test by two weeks of age. Premature infants and those with illnesses should be tested at or near seven days of age, but in all cases before newborn nursery discharge.

Discussion

In 1996, the USPSTF reviewed the evidence for screening for PKU in newborns and found that the benefits substantially outweighed the harms of screening. The benefits of screening for PKU continue to be well established. This update focused on a search for new and substantial evidence on the benefits and harms of screening.4 The USPSTF found no new substantial evidence on the benefits and harms of screening for PKU and, therefore, reaffirms that physicians should screen for PKU in newborns. The 1996 recommendation statement, the 1996 evidence report, and the summary of the updated literature search can be found at http://www.uspreventiveservicestaskforce.org/recommendations.htm.

Recommendations from Other Groups

According to the American Academy of Pediatrics, PKU screening should occur in newborns older than 24 hours and younger than seven days. Infants screened before 24 hours of life should be rescreened by two weeks of age to detect possible missed cases. All infants should be screened at the time of nursery discharge or transfer, regardless of age. Sick infants and premature infants should be screened by seven days of age, regardless of feeding history or antibiotic treatment.5 The American Academy of Family Physicians strongly recommends that physicians screen neonates for PKU.6 The American College of Medical Genetics recommends that PKU screening be mandated as part of state newborn screening programs.7


This recommendation statement was first published in Ann Fam Med. 2008;6(2):166.

The U.S. Preventive Services Task Force Recommendations are independent of the U.S. government. They do not represent the views of the Agency for Healthcare Research and Quality, the U.S. Department of Health and Human Services, or the U.S. Public Health Service.

REFERENCES

1. U.S. Preventive Services Task Force. Screening for phenylketonuria. In: Guide to Clinical Preventive Services. 2nd ed. Washington, DC: U.S. Department of Health and Human Services. 1996.

2. National Institutes of Health Consensus Development Panel. National Institutes of Health Consensus Development Conference Statement: phenylketonuria: screening and management, October 16–18, 2000. Pediatrics. 2001;108(4):972–982.

3. Pandor A, Eastham J, Beverley C, Chilcott J, Paisley S. Clinical effectiveness and cost-effectiveness of neonatal screening for inborn errors of metabolism using tandem mass spectrometry: a systematic review. Health Technol Assess. 2004;8(12):iii,1–121.

4. Mabry-Hernandez I, Wolff T, Green K. Screening for phenylketonuria: a literature update for the U.S. Preventive Services Task Force. Rockville, Md.: Agency for Healthcare Research and Quality; 2008. AHRQ publication no. 08-05110-EF-1. http://www.ahrq.gov/clinic/uspstf08/pku/pkuart.htm. Accessed October 7, 2009.

5. Newborn screening fact sheets. American Academy of Pediatrics. Committee on Genetics. Pediatrics. 1996;98(3 pt 1):473–501.

6. American Academy of Family Physicians. Summary of recommendations for clinical preventive services. Revision 6.8; 2009. http://www.aafp.org/online/etc/medialib/aafp_org/documents/clinical/CPS/rcps08-2005.Par.0001.File.tmp/RCPS_August2005.pdf. Accessed October 7, 2009.

7. Newborn screening: toward a uniform screening panel and system. Genet Med. 2006;(8 suppl 1):1S–252S.

This summary is one in a series excerpted from the Recommendation Statements released by the U.S. Preventive Services Task Force (USPSTF). These statements address preventive health services for use in primary care clinical settings, including screening tests, counseling, and preventive medications.

The complete version of this statement, including supporting scientific evidence, evidence tables, grading system, members of the USPSTF at the time this recommendation was finalized, and references, is available on the USPSTF Web site at http://www.ahrq.gov/clinic/uspstf/uspsspku.htm.



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