Incorporation of second-tier tests and secondary biomarkers to improve positive predictive value (PPV) rate in newborn metabolic screening program

Abstract

Background: Nowadays, neonatal screening has become an essential part of routine newborn care in the world. This is a non-invasive evaluation that evaluated inborn errors of metabolisms (IEMs) using tandem mass spectrometry (LC-MS/MS) for the evaluation of the baby's risk of certain metabolic disorders. Methods: This retrospective study was conducted on 39987 Iranian newborns who were referred to Nilou Medical Laboratory, Tehran, Iran, for newborn screening programs of IEMs. We incorporated second-tier tests and secondary biomarkers to improve positive predictive value (PPV). Results: Statistical data were recorded via call interviewing in 6–8 months after their screening tests. The overall prevalence of IEM was 1:975. The mean age of all participants was 3.9 ± 1.1 days; 5.1% of participants were over 13 days and 7.7% were preterm or underweight. A total of 11384 (29.4%) of the cases were born in a consanguineous family. The type of delivery was the cesarean section in 8332 (51.3%) valid cases. The neonatal screening results had an overall negative predictive value (NPV) of 100% and the overall PPV of 40.2%. The false-positive rate was 0.15%. Conclusion: This study showed a high incidence of metabolic disease due to a high rate of consanguineous marriages in Iran and indicated that incorporation of second-tier tests and secondary biomarkers improves PPV of neonatal screening programs.