The Central Biochemistry Laboratory (CBL) serves the subjects and investigators of the continuing Prospective Study of Chronic Kidney Disease in Children (CKiD). The CBL provides participating clinical sites with protocols, kits, reagents, supplies, and transportation required for collecting blood and urine for analysis at URMC and other laboratories. Blood analytes include electrolytes, BUN, creatinine, glucose, calcium, phosphorus, albumin, uric acid, lipid screen, hsCRP, intact PTH, and cystatin C. Urine analytes include creatinine and protein. The CBL has determined optimal conditions for transporting these analytes, and provides ambient shippers for each visit and quarterly dry ice shippers for frozen specimens. The CBL also provides the kits and instructions for collection and shipment of blood, plasma, sera, urine, hair, and nail samples to NIH repositories. Biochemical data from each CKiD visit are reviewed and entered into Nephron, the CKiD data base. The CBL provides training at annual CKID meetings and is readily available to provide information, instruction, and support during CKiD visits. The CBL contributes expertise in performing biochemical assays and clinical interpretation of the results. The CBL collaborates regularly with the Data Coordinating Center to provide expertise regarding laboratory medicine, optimizing GFR studies and generating GFR estimating equations, maintaining the Manual of Procedures, assuring the quality control of all assays, and providing continuity of biochemical assays through changes in instrumentation. The CBL participates in all Steering Committee meetings and conference calls and collaborates with investigators in the generation of abstracts, presentations, and manuscripts. The proposed aims of the CBL center on continuing to provide accurate, precise, and efficient measures of biochemical measurements of general kidney health and contribute as a scientific partner to further the research agenda of the CKiD Consortium. The CBL will continue to provide the laboratory kits for collection, handling, and transport of samples, accurately receive, process, and analyze these samples on a day-to-day basis, and provide timely data entry into Nephron. The CBL has established a new subcontract with the UMN ARDL that will assure accurate measurement of iohexol concentrations (and hence GFR) during this project period. Accordingly, the CBL will continue to develop and optimize GFR estimating equations using conventional biomarkers in Cohort 3 subjects and other participants with Stage 1 CKD, and in those having received a kidney transplant. The CBL has completed work on concept sheets showing that hyperuricemia is associated with more rapid renal progression and that microalbuminuria is no better predictor of renal progression than is urinary protein. The CBL will next examine beta trace protein to determine if it is useful in predicting GFR. The long term goal is to better characterize the CKiD population biochem...