Heart Biomarker Evaluation in Apnea Treatment

4.4.4 Urine Processing

When the patient voids the urine volume and time of collection is recorded. The volume measurement can be approximate as this measurement does not need to be precise. The urine is then divided into two containers processed immediately. One container is just urine (no additives) and the other container has 25 mL of 1M acetic acid to preserve the urine (final pH < 3). Both containers should be labeled with the participant ID number. The 7 digit ID number followed by a 4 denotes urine samples. The containers should also be clearly marked with labels for the plain urine and the urine + acid. (This can be done with colored labels if desired, a yellow label for the plain urine and a green label for the urine + acid.) The samples should be processed and refrigerated (4°C) promptly (within 15 minutes) after removal from the patient’s room.

To ensure safe handling of the urine and acid preservative containers with covers are advised. Urine and acid should be carefully decanted down the side of the containers to avoid splashing.

Once the collection is received, measured and divided, the urine and acid in the second container should be gently swirled to mix the contents, again taking care to avoid splashing. Note: we recommend that this procedure be carried out in a fume hood. While not toxic at the levels used for this study, acetic acid has a strong, unpleasant odor and the addition of acid to the urine may generate a small amount of heat. Once the acid is added and the container is capped, the container can be safely removed for storage in the refrigerator.