Bilancio G, et al. - Researchers determined the methodology of saliva tests for creatinine, uric acid, and potassium as these analytes have previously been reported to be measurable in saliva. In addition, they focused on the correlations between plasma and saliva levels. Participants were healthy volunteers (n=15) and nephropathic patients (n=42) for methodological analyses and for plasma-saliva correlations (35 non-dialysis and 7 dialysis), respectively. Following overnight fast, early morning collection of blood and saliva, unless otherwise indicated, was performed and lab tests were carried out in fresh samples by automated biochemistry (standard). Blind duplicates, diverse collection mouth sites, day-to-day variability, different collection times, and freezing-thawing impacts were included in methodological analyses. For creatinine, uric acid, and potassium, saliva levels were measurable and were found to be correlated with plasma levels. As the saliva levels of these analytes are lowered by later collection times or freezing, early morning fasting fresh saliva samples are advisable.