Newborn screening for galactosemia: a review of 5 years of data and audit of a revised reporting approach.

BACKGROUND: Availability of the galactose-1-phosphate uridyltransferase (GALT) assay for newborn (NB) screening has improved identification of classic galactosemia. Previously defined critical cutoffs for total galactose (Gal), typically 1.110 mmol/L (20 mg/dL), are still in use in laboratories measuring total Gal for the diagnosis of nonclassic galactosemias. Urgent notification/referral to a treatment center follows, although few of the NBs will need treatment. METHODS: We reviewed all NB galactosemia-screening results and their corresponding clinical outcomes over a 5-year period (first phase, 1.32 x 10(6) NBs) and then over a 2-year period (second phase, 274 960 NBs). Each NB was screened for Gal and GALT. When Gal was increased and/or GALT was deficient, testing for percentage galactose-1-phosphate and/or DNA testing for common GALT mutations were performed. RESULTS: Of 209 reported positive results, 89% did not indicate GALT deficiency. These non-GALT-deficient results represented mostly clinically benign cases with a Gal threshold of > or = 1.110 mmol/L (> or = 20 mg/dL). The positive predictive value of a GALT cutoff of < or = 40 micromol/L was 83%. After a protocol change that redefined a critical result as a GALT value < or = 40 micromol/L and/or a Gal value > or = 1.665 mmol/L (> or = 30 mg/dL), results were monitored for an additional 2 years. The new protocol dramatically reduced the number of urgent calls/referrals and reduced the total number of referrals by nearly half. CONCLUSIONS: Use of a GALT cutoff of < or = 40 micromol/L/L and a Gal cutoff of > or = 1.665 mmol/L (> or = 30 mg/dL) for urgent notification/referral dramatically reduces false positives and unnecessary follow-up, thereby reducing the stress on healthcare resources.

Alternative DNA-based newborn screening for glucose-6-phosphate dehydrogenase deficiency.

Newborn screening for G6PD deficiency has been carried out in several countries for more than 25 years. A semi-quantitative enzymatic assay has been used in most laboratories, however, heat inactivation during the summer can cause a significant increase in the false positive rate for this assay. We have developed an alternative DNA-based newborn screening assay for the detection of common mutations within the G6PD gene. The panel of mutations includes the common African A- mutation (G202A;A376G), the common Mediterranean mutation (C563T), and two common Chinese mutations (G1376T and G1388A). A parallel study was performed through screening a total of 4245 neonatal specimens using both the enzymatic and the DNA-based assays. In this population, 49 newborns were identified as hemizygous or homozygous for the A- mutation with an average enzyme activity of 59 microM, 323 were identified as a carrier or unaffected with an average enzyme activity of 208 microM, and no mutation was detected for the remaining 3873 specimens with an average enzyme activity of 234 microM. With this panel of mutations, more than 90% of all affected infants can be identified in our population.