title: Can salivary creatinine and urea levels be used to diagnose chronic kidney disease in children as accurately as serum creatinine and urea levels? A case-control study.
abstract: OBJECTIVE
  Children with chronic kidney disease (CKD) develop many metabolic changes in blood that often necessitate frequent biochemical analysis. Serum analysis is an invasive and painful procedure. It would be highly beneficial if a noninvasive alternative process to serum analysis in children were identified. Saliva can be collected noninvasively, repeatedly, and without the use of healthcare personnel. The aims of this study were to compare serum and salivary urea and creatinine levels in children with CKD and healthy controls, and to determine if salivary creatinine and urea levels can be used to diagnose CKD in children as accurately as serum creatinine and urea levels.
  
  
  METHODS
  This case-control study included 35 children with CKD and 28 healthy children as controls. Saliva and blood samples were collected for measurement of urea and creatinine levels. The urea and creatinine levels in serum and saliva in the CKD and control groups were compared using the independent samples Mann-Whitney U test. Correlations between the serum and salivary urea and creatinine levels were determined using Pearson's correlation coefficient. Receiver operating characteristic analysis was used to assess the diagnostic performance of salivary creatinine and cutoff values were identified.
  
  
  RESULTS
  In the CKD group, the mean salivary creatinine level was 0.45 mg/dL and the mean salivary urea level was 0.11 mg/dL, versus 28.83 mg/dL and 21.78 mg/dL, respectively, in the control group. Stage 4 and 5 CKD patients had a mean salivary urea level of 31.35 mg/dL, as compared to 17.78 mg/dL in the control group. Serum urea and creatinine, and salivary creatinine were significantly higher in the CKD patients (regardless of disease stage) than in the controls (p < .05). The salivary urea level was significantly higher in the stage 4 and 5 CKD patients than in the controls (p < .05). There was a positive correlation between serum and salivary creatinine. The area under the curve for salivary creatinine was 0.805. The cutoff value for salivary creatinine was 0.125 mg/dL, with a sensitivity of 82.9% and specificity of 78.6%.
  
  
  CONCLUSIONS
  Based on the positive correlation between the serum and saliva creatinine levels observed in the present study, we think saliva analysis could be used as a noninvasive alternative to blood analysis for diagnosing CKD in children.
authors.affiliation: a Department of Pediatric Nephrology , Antalya Research and Education Hospital , Antalya , Turkey.
authors.forename: Rahime
authors.initials: R
authors.lastname: Renda
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D003404:Creatinine / Q000032:analysis* / Q000097:blood; D005260:Female; D006801:Humans; D007677:Kidney Function Tests; D008297:Male; D012372:ROC Curve; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000175:diagnosis*; D012463:Saliva / Q000737:chemistry*; D014508:Urea / Q000032:analysis* / Q000097:blood
chemical_list: D014508:Urea; D003404:Creatinine
keywords: Serum; chronic kidney disease; creatinine; saliva