Comparison of serum and salivary creatinine levels in preterm neonates

Introduction: In recent years, saliva has been frequently tested as an alternative biological sample for diagnosing various diseases. Various substances reach the saliva through endogenous synthesis in acinar cells or from plasma. Passive diffusion, transudation, diffusion, or selective transport are how these substances cross from plasma to saliva. There are a small number of studies in children and adults that have examined renal function and the ratio of serum and salivary creatinine. To date, no study has been conducted that examined the existence of this correlation in neonates. Our study aimed to examine whether there is a correlation between serum and salivary creatinine values in preterm infants. Methods: We conducted a prospective study that included 30 neonates, in whom serum and salivary creatinine levels were measured simultaneously in two-time spots. Results: The mean value of salivary to serum creatinine (sCr) ratio was 0.700. Salivary to sCr ratio was statistically significantly higher in newborns of gestational age (GA)<28 gestational weeks (mean value 0.825), compared to children with GA≥28 gestational weeks (mean value 0.566), student t-test; p=0.003. Logistic regression showed that the correlation between serum and salivary creatinine levels was more coherent in newborns with GA<28 weeks. Conclusions: In this study, it was examined for the first time whether there is a correlation between the values of serum and salivary creatinine in preterm infants. We found that the correlation between serum and salivary creatinine levels is strong in newborns with GA<28 weeks.