0008 Comparing 6-Sulfatoxymelatonin Collected from Liquid and Dried Urine Samples: A Proof-of-Concept Study

Introduction Urine collection for quantification of 6-sulfatoxymelatonin (aMT6s) is common; however, obtaining samples is challenging for field-based research, as participants may not be able to transport liquid samples to a laboratory. Dried urine collection represents a potential solution, as dried samples can be shipped without risk of leaking. This proof-of-concept study explored the comparability of aMT6s derived from liquid versus dried urine. Methods Participants were N=15 healthy individuals affiliated with the University of Arizona. Participants self-collected five cumulative voids over 24 consecutive hours at home using a study-provided container (i.e., urine hat/urinal). These voids included all urine produced: 1) in the hour prior to bedtime on night 1; 2) overnight including the first morning void; 3) the three hours after the first morning void; 4) the four hours after the third collection; and 5) approximately four hours prior to bedtime on night 2. At the close of each collection window, participants saturated a piece of filter paper and filled a 70mL container with the collected urine. Remaining urine was discarded and filter papers were left to dry for 24 hours, during which time liquid samples were stored in participants’ home refrigerators. Samples were then hand-delivered to the University of Arizona and stored at –80C until they were shipped in a single batch to a professional laboratory for analysis using mass spectrometry. aMT6s levels were adjusted for creatinine. Results Participants were M=34 years old (range: 20–39) and the majority was White (60%), female (93%), and non-Hispanic (53%). Seventy three of 75 expected samples were received; two were missing because no urine was produced during the collection window. One spurious sample was removed, leaving 72 samples for analysis. There was a strong positive relationship between aMT6s levels across liquid and dried samples (r=0.987, p< 0.001). Per Bland-Altman analysis, 94% of samples were within the limits of acceptability. Conclusion Pending confirmation with a larger sample, dried urine seemingly yields equivalent information about aMT6s as liquid urine. This method could expand the feasibility and convenience of aMT6s assessment in various populations. Support (if any) Funding provided by the University of Arizona College of Nursing. Support for materials provided by Precision Analytical.