Application of Molecular Genetics in Public Health: Improved Follow-up in a Neonatal Hemoglobinopathy Screening Program

Newborn screening for the hemoglobinopathies has been shown to reduce morbidity and mortality, particularly for sickle cell anemia, by facilitating initiation of penicillin prophylaxis by 4 months of age. The purpose of the current investigation was to determine whether molecular genetic follow-up testing could be introduced into a neonatal hemoglobinopathy screening program and, if successfully introduced, whether it would reduce time to diagnostic confirmation. Between July 1, 1991, and October 7, 1992, 518 original dried blood specimens were referred from the Texas Department of Health Neonatal Hemoglobinopathy Screening Program for molecular genetic follow-up testing. Allele-specific cleavage (ASC) after amplification with matched and mismatched polymerase chain reaction primers was compared to allele-specific oligonucleotide (ASO) hybridization. By November 2, 1992, molecular genetic analyses were definitive in 506, and agreement was observed between ASC and ASO hybridization in all specimens analyzed. Approximately 13% of those initially screened FS were considered probable S/β-thal by DNA and RNA testing. Rapid molecular genetic analysis contributed to a substantial reduction of the mean age at confirmation by approximately 50%, to about 2 months of age. ASC is a reliable method for molecular genetic analysis of dried blood specimens, providing methodology which can be readily automated. An automated method is demonstrated that is based on microtiter plate technology and will significantly reduce labor intensity and costs, while increasing sample throughput. Even with current manual testing methods, DNA and RNA analysis of initial newborn screening specimens will reduce the age at confirmation well under 4 months, the age cut-off for effective initiation of penicillin prophylaxis.