Newborn blood spot screening is undertaken with the primary assumption that early diagnosis and treatment is a good investment of public resources, both for the individuals tested and for society. Although some effects of improved outcomes seem self-evident, for most newborn-screened disorders there is no comprehensive, long-term assessment of outcomes for children identified by screening. To verify the effectiveness of early identification, intervention, and treatment, longitudinal assessment of outcomes is essential. A better understanding of the natural histories of rare metabolic disorders and the effectiveness of current treatments is necessary to provide optimum care and promote the best possible outcomes for children with these conditions. The Inborn Errors of Metabolism Collaborative (IBEMC), consisting of 13 clinics from 10 states, will collect longitudinal data that capture the clinical progress of persons affected with conditions identified by newborn screening, focusing on inborn errors of metabolism. Data will be used to better define the natural histories and understand the effect of treatment interventions. The database will allow for: 1. Investigation of the relationship among NBS values, genotype, and early manifestations as well as complications of inborn errors of metabolism;2. Evaluation of the impact of early identification and intervention on metabolic conditions;3. Informed decision making about optimal public health investment in NBS;4. Clarification of the previously undefined natural history of very rare metabolic conditions;and 5. Identification of current nutritional and therapeutic interventions for children with metabolic conditions and evaluation of their effectiveness. The IBEMC will build on the work of the HRSA-funded Region 4 Genetics Collaborative and be developed in collaboration with other national efforts, including the Newborn Screening Translational Research Network. The project will establish innovative practices to engage clinicians in a culture of collaboration, provide incentives to ensure collection of both intake and interval data, as well as offer supports that encourage data analysis. These efforts will result in investigations that provide a foundation for clinical trial design and improved treatment for children with inborn errors of metabolism. RELEVANCE: As a sufficient number of cases are entered for the rarer disorders, research will provide evidence as to the efficacy of early diagnosis and treatment. If research does not support the assumption on which NBS is based, i.e., early diagnosis and treatment are good investments of public resources, both for the individuals tested and for society, the NBS public health paradigm may change. It is possible that the increase in knowledge about the natural history of IBEM will lead to a change in how conditions are added to the NBS panel and that the conditions currently in the panel may be reviewed and revised.