Sarafoglou K, Rodgers J, Hietala A, Matern D, Bentler K. Expanded Newborn Screening for Detection of Vitamin B12 Deficiency. JAMA. 2011;305(12):1198–1200. doi:10.1001/jama.2011.310
To the Editor: When undiagnosed, infant vitamin B12 deficiency can result in anemia, failure to thrive, developmental regression, and neurological deficits and is most commonly caused by maternal vitamin B12 deficiency.1 Biochemically, vitamin B12 deficiency leads to an accumulation of total homocysteine (tHcy), methylmalonic acid (MMA), and propionylcarnitine (C3). Although vitamin B12 deficiency is not a primary target of newborn screening (NBS) programs, measurement of C3 may incidentally identify vitamin B12–deficient newborns. However, first-tier screening is limited because C3 levels may not be sufficiently high during the first days of life when most NBS samples are collected.2 Levels of MMA and tHcy are more sensitive markers of vitamin B12 status than serum B12 levels in adults,3 have a strong inverse relationship with serum B12 levels,4 and are usually elevated in infants who are vitamin B12 deficient before hematologic or neurologic findings develop.2 Through the public-private partnership between the Minnesota Department of Health, Mayo Clinic, and University of Minnesota, a lower first-tier cut-off level of C3 was applied (>9.2 μmol/L to >5.25 μmol/L) and second-tier testing of MMA and tHcy levels in presumptive-positive NBS specimens was introduced in 2005.5
A population-based study of 363 649 infants born in Minnesota was conducted between January 1, 2005, and December 31, 2010. Newborn screening samples with elevated C3 levels, a C3 to acetylcarnitine (C3/C2) ratio of 0.1 or greater, or a C3 to palmitoylcarnitine (C3/C16) ratio of 2 or greater had second-tier testing of tHcy (abnormal, >15 μmol/L) and MMA (abnormal, >5 μmol/L) on the same sample.5 (To convert tHcy to mg/dL, divide by 7.397.) All newborns with positive NBS results and some of their mothers underwent further laboratory testing. An additional newborn from another state whose first-tier NBS findings were normal presented at age 2 months with clinical complications of vitamin B12 deficiency and required prolonged hospitalization. His original NBS sample was retrospectively analyzed to determine if the Minnesota 2-tier protocol would have led to identifying the infant as vitamin B12 deficient. The University of Minnesota institutional review board approved review of medical records and waived informed consent.
Of 46 newborns with abnormal C3 levels or related ratios identified in Minnesota, 11 had vitamin B12 deficiency secondary to maternal vitamin B12 deficiency (Table 1 and Table 2) for a detection rate of 3.02 per 100 000 live births; 22 findings were false positives; 1 declined follow-up testing; 1 had unconfirmed vitamin B12 deficiency; 3 had cobalamin C defects; and 2 had methylmalonic acidemias. Five were homozygous and 1 a carrier for transcobalamin receptor defects. Newborn screening led to the identification of vitamin B12 deficiency in 8 of 11 mothers whose status was previously unrecognized. All 11 newborns were asymptomatic when treatment was initiated (Table 2), and subsequently all biochemical markers normalized without clinical signs of vitamin B12 deficiency. Retrospective analysis using the 2-tier protocol of the original NBS sample of the symptomatic infant screened by another state had positive results (Table 1, case 12).
A recent survey of 12 state NBS programs (including Minnesota) identified 32 cases of nutritional vitamin B12 deficiency, for a rate of 0.88 per 100 000 newborns.6 After implementing a lower C3 first-tier cut-off level and second-tier testing of MMA and tHcy levels in NBS specimens, the detection rate in Minnesota of vitamin B12–deficient infants was considerably higher (3.02/100 000 live births). None of the 11 infants would have been identified by using the previous C3 cut-off value, potentially explaining the reason no cases of infant vitamin B12 deficiency were identified by NBS before 2005 in Minnesota.
Based on the Minnesota experience, vitamin B12 deficiency occurs more frequently than is currently recognized. Given the important role vitamin B12 plays in DNA synthesis and central nervous system function, and the difficulty in diagnosing vitamin B12 deficiency in infancy because of nonspecific clinical findings, early identification and initiation of treatment are crucial to avoid potentially devastating and irreversible neurologic damage.
Author Contributions: Dr Sarafoglou had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Sarafoglou, Matern.
Acquisition of data: Sarafoglou, Rodgers, Hietala, Matern, Bentler.
Analysis and interpretation of data: Sarafoglou, Rodgers, Matern, Bentler.
Drafting of the manuscript: Sarafoglou, Matern, Bentler.
Critical revision of the manuscript for important intellectual content: Sarafoglou, Rodgers, Hietala, Matern, Bentler.
Administrative, technical, or material support: Hietala, Matern.
Study supervision: Sarafoglou, Bentler.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.
Funding/Support: All work performed for this study was done as part of the unique public-private partnership that exists between the Minnesota Department of Health, the Mayo Clinic, and the University of Minnesota Amplatz Children's Hospital.
Role of the Sponsor: The funding organizations had no role in the design and conduct of the study; in the collection, analysis, and interpretation of the data; or in the preparation, review, or approval of the manuscript.
Additional Contributions: Susan A. Berry, MD, and Chester B. Whitley, MD, PhD, University of Minnesota Amplatz Children's Hospital, and Dimitar K. Gavrilov, MD, PhD; Devin Oglesbee, PhD; Kimiyo M. Raymond, MD; Piero Rinaldo, MD, PhD; and Silvia Tortorelli, MD, PhD, Mayo Clinic College of Medicine, provided clinical and laboratory testing information. Gary L. Hoffman, BS, Wisconsin State Laboratory of Hygiene, provided NBS information and reviewed the manuscript. None of the individuals received compensation for the contributions.