Collect 24 hour urine specimen. Add 25 mL of 50% glacial acetic acid (15 mL for pediatric patients) to container prior to start of collection. Following collection, mix well, measure 24 hour urine volume, aliquot 10 mL into a plastic urine container and refrigerate. Record total 24 hour urine volume and collection dates/times on request form. Specimens with no preservative are also acceptable: add 50% glacial acetic acid to container following collection, mix well and send 10 mL aliquot (preferred); alternatively a non-acidified aliquot will be accepted. Random samples will be accepted on children less than 10 years old, in which case the HVAR test code must be ordered instead of the HVA test code.