Draw blood into an EDTA tube. Keep tube at room temperature. Centrifuge at room temperature. Transfer the plasma into a plastic transport tube and Freeze immediately and maintain frozen until tested. IT IS CRITICAL THAT THE PLASMA BE TRANSFERRED AND FROZEN AS QUICKLY AS POSSIBLE TO PREVENT CRYOACTIVATION OF PROTEIN TO RENIN (WHICH RESULTS IN FALSELY ELEVATED RENIN LEVELS). To avoid delays in turnaround time when requesting multiple tests on frozen samples, PLEASE SUBMIT SEPARATE FROZEN SPECIMENS FOR EACH TEST REQUESTED. The patient's posture at the time of collection should be noted (see Patient Preparation).