 One batch of dialysate samples will be packed on dry ice sufficient for 2 days and shipped to a location to be determined by Merck. One batch of blood and urine samples will be packed in dry ice sufficient for 2 days and shipped to a location to be determined by Merck. The second batch of samples dialysate, blood, and urine will be sent to a central laboratory Quest Diagnostics, Inc for serum, urine, and dialysate creatinine and urea assay and dialysate dextrose concentration assay. 