Comparison and correlation study of polar biomarkers of CKD patients in saliva and serum by UPLC-ESI-MS

Abstract

Abstract:There are abundant reports on the use of aromatic amino acids and creatinineas biomarkers in serum and urine forCKD(chronic kidney disease). However, investigationsinto these bio-species in bio-fluids, such as saliva and sweat, are rarely reported. Increasing interest in non-invasive methods for medical diagnosis advocates for the testing of these bio-fluidstoidentify potential biomarkers for prompt clinical andpreliminary screening using advanced analytical equipment.Unstimulated whole saliva samples were obtained from twenty-seven CKD patients and an equivalent number of healthy individuals. Saliva was assayed with ultra-performance liquid chromatography coupled with electro-spray ionization tandem mass spectrometry (UPLC-ESI-MS) in hydrophilic interaction chromatography mode. The data were analyzed using a student’s t test and receiver operatingcharacteristic(ROC) to evaluate the predictive power of several potential biomarkers (P<0.01) in saliva for preliminary CKD screening. Through testing of salivary samples between CKD patients and healthy individuals, we found three possible salivary biomarkers that demonstrated significant differences(P<0.01) from the nine reported species in serum and/or urine. The area under the curve (AUC) values for control vs CKDpatientsfor on L-phenylalanine, L- tryptophan, and creatinine were 0.863, 0.834, and 0.916, respectively. This is the first report to compare serum and urine biomarkers in saliva between CKD patients and healthy people. This study explores the potential of CKD diagnosis by saliva, and demonstrates a positive correlation between salivary and serum creatinine.