Introduction of a Novel Cut-off in Newborn Screening of Galactosemia; A Cohort Study

Background: The current newborn screening for Classic Galactosemia (CG) presents significant challenges, including a low positive rate and a high false-positive rate. Objectives: In this study, we aimed to establish new cut-off values (COVs) for CG screening and introduce a novel approach. Methods: Total galactose (TGAL: The sum of galactose (Gal) and galactose-1-phosphate (G-1-P)) levels of all newborns born in Fars, Iran, from August 2006 to December 2020, were reviewed to establish cut-off ranges. A receiver operating characteristic (ROC) curve analysis was performed to define an optimal COV. Results: Out of 1,187,436 newborns, 4,893 (0.41%) were recalled for further evaluation due to an initial TGAL ≥ 4 mg/dL from a positive screening test, with 160 (3.26%) confirmed to have CG. In the initial negative screening results, nine infants were missed as false negatives. An area under the curve of 0.868 suggested that TGAL is a reliable indicator for distinguishing galactosemia from normal subjects. Receiver operating characteristic curve analysis indicated that a cut-off value (COV) of 5.2 mg/dL provided a sensitivity and specificity of 80.0% and 81.3%, respectively, making it an optimal conservative value for deciding on further recall in the Iranian setting. Additionally, a COV of 7.35 mg/dL demonstrated a sensitivity of 71.3% and specificity of 95.7%, making it a suitable cut-off for immediate referral. Conclusions: We proposed a novel protocol for newborn screening in Iran, establishing a TGAL level of 5.2 mg/dL as a conservative cut-off for CG screening, showing excellent sensitivity while ensuring specificity for recalling suspicious cases. Furthermore, a cut-off of 7.35 mg/dL was identified for prompt consideration of urgent treatment.