Saliva for assessing creatinine, uric acid, and potassium in nephropathic patients

Abstract

Background Lab tests on saliva could be useful because of low invasivity. Previous reports indicated that creatinine, uric acid, and potassium are measurable in saliva. For these analytes the study investigated methodology of saliva tests and correlations between plasma and saliva levels. Methods The study enrolled 15 healthy volunteers for methodological analyses and 42 nephropathic patients for plasma-saliva correlations (35 non-dialysis and 7 dialysis). Saliva was collected by synthetic swap right after venipuncture for blood withdrawal. Blood and saliva, unless otherwise indicated, were collected early in the morning after overnight fast and lab tests were performed in fresh samples by automated biochemistry (standard). Methodological analyses included blind duplicates, different collection mouth sites, day-to-day variability, different collection times, and freezing-thawing effects. Analyses on plasma-saliva correlations included post-dialysis changes. Results For saliva lab tests of all analytes, blind duplicates, samples from different mouth sites or of different days were not significantly different but were significantly correlated (differences ≤14.4%; R ≥ 0.620, P ≤ 0.01). For all analytes, mid-morning saliva had lower levels than but correlated with standard saliva (differences ≥15.8%; R ≥ 0.728, P ≤ 0.01). Frozen-thawed saliva had lower levels than fresh saliva for uric acid only (− 17.2%, P < 0.001). Frozen-thawed saliva correlated with fresh saliva for all analytes (R ≥ 0.818, P ≤ 0.001). Saliva and plasma levels differed but correlated with plasma for creatinine (R = 0.874, P < 0.001), uric acid (R = 0.821, P < 0.001) and potassium (R = 0.767, P < 0.001). Post-dialysis changes in saliva paralleled post-dialysis changes in plasma. Conclusion Saliva levels of creatinine, uric acid, and potassium are measurable and correlated with their plasma levels. Early morning fasting fresh saliva samples are advisable because later collection times or freezing lower the saliva levels of these analytes.

Non-invasive determination of uric acid in human saliva in the diagnosis of serious disorders

“…Concentrations of UA in the saliva of healthy individuals is 199 ± 27 μmol/L and comparable to concentrations 120-400 μmol/L observed in the serum [6]. Earlier studies reported a linear relationship between serum and salivary UA levels in most cases [1,6,[9][10][11][12].…”

“…Unfortunately, these tests were performed only with a single participant. Bilancio et al [12] compared effect of storage, time of collection, day-to-day variability, and site of collection of UA in saliva. Mid-morning saliva had lower levels of 184 ± 102 μmol/L while standard morning saliva content was 261 ± 166 μmol/L.…”

“…First, the cotton swab is placed under the tongue for 5 min and then centrifuged in the Salivette tube at 1,000 × g for 10 min. The advantages of this system over the typical spitting in passive drool to a tube are the simplicity and enhanced hygiene of the collection, the lower viscosity of the saliva, as well as the ease of removal of dead cells, glycoproteins, and other subcellular substances [12,38,46,50].…”

Salivary Biomarkers and Their Correlation with Pain and Stress in Patients with Burning Mouth Syndrome

“…As a reactive oxygen species scavenger, it helps stabilize arterial pressure and oxidative stress [21,[34][35][36]. In turn, alterations in its levels in saliva were associated with acute stress [34] and different local and systemic pathologies such as oral lichen planus [37] or nephropathies [38]. Previous studies that evaluated salivary uric acid in patients with BMS did not find statistically significant changes as compared with healthy controls [16,20], although these studies did not make corrections for total protein content.…”

Selected salivary parameters in children with idiopathic nephrotic syndrome: a preliminary study

“…Therefore, salivary constituents of serum origin can reflect the abnormalities in the blood composition associated with systemic diseases [ 9 , 10 ]. In patients with chronic kidney disease (CKD), higher contents of urea, uric acid and creatinine in saliva were found [ 11 – 13 ]. Salivary levels of cortisol, nitrite, uric acid, sodium, chloride, pH, amylase, and lactoferrin have been reported to be markers related to end-stage renal disease [ 14 ].…”