PROJECT SUMMARY An important goal of the NIDDK is to identify infants with biliary atresia (BA) earlier, because treatment before 30-45 days of life correlates with the best chances of avoiding need for liver transplantation. However, early identification is difficult, because infants often appear asymptomatic in the first weeks of life. One solution to this problem is screening newborns with serum conjugated bilirubin measurements, which are elevated at birth in BA; however, this method requires a separate blood draw and individual birth hospitals to interpret and follow-up abnormal results. Another possible solution is to screen newborns with dried blood spot (DBS) cards which are already collected from all infants as part of existing state newborn screening programs. This application’s long, broad-term objective is to assess whether a new method which approximates conjugated bilirubin levels from DBS cards can potentially be integrated with state newborn screening protocols. In Aim 1, we will improve the new method by first establishing an experimental system that replicates the analytical workflow of state laboratories. With this system, the new method’s parameters will be optimized. In Aim 2, we will test the new method using newborn DBS cards which were previously collected and are stored at the Texas State Department of Health Services. DBS cards from healthy newborns will be analyzed, to determine the new method’s positive rate. In addition, DBS cards from newborns with BA will be analyzed, to determine if the method is as sensitive for BA as serum conjugated bilirubin testing. Results from this study should determine whether the new method can be used to incorporate BA screening into current state newborn screening protocols. The findings will help guide the best approach for future prospective screening implementation studies, with the ultimate goal of identifying BA in the first weeks of life and reducing BA’s significant pediatric liver transplantation burden.