For most amino acids disorders, plasma is the preferred sample type. For plasma samples, at least 1ml is required. 3 ml of whole blood in a green top, sodium heparin tube can also be sent.
Please be aware that urine amino acid values are based on creatinine concentration. As the concentration of urine varies greatly, levels can be falsely elevated or lowered. In cases of suspected transport defects, such as cystinuria, urine is preferred. Urine samples should be at least 10 ml of a random catch. 24-hour collection is preferred.
Amino acid analysis may also be performed on cerebral spinal fluid (CSF).