Comparison of Serum and Salivary Alpha-Fetoprotein Levels in Pregnancies Complicated with Neural Tube Defects

Objective: To compare the serum and salivary values of alpha-fetoprotein (AFP) used in screening neural tube defects (NTD) during pregnancy. To investigate whether saliva can be used instead of serum in NTD screening. Method: The study was conducted between May 2018 - November 2019 at Adiyaman University. The study included 41 pregnant women complicated by NTD and 44 healthy pregnant women. Three ml venous blood and 2 ml saliva samples were taken from both groups. Serum and saliva samples were not diluted. AFP concentration was measured at 450 nm by using commercially available enzyme-linked immunoassay. The intra-, and inter-test assay coefficients (CVs) of the kit were <8% and <10%, respectively. SPSS 21 program was used for data analysis. Mann-Whitney Test was used for the analysis of continuously changing parameters. The correlation coefficient was calculated by Spearman test. A p value of less than 0.05 was accepted for statistical significance. Results: When serum and salivary AFP values were compared between the two groups, the AFP values were found to be higher in both NTD group samples (p<0.001, p<0.001). In both groups, correlation analysis for serum and salivary AFP values showed a strong positive correlation (r=0.730, p<0.001). When the cut-off value for serum AFP is taken as 0.26, NTD can be determined with 100% sensitivity and 90% specificity (AUC: 0.932, p<0.001). When the cut-off value for salivary AFP is taken as 0.034, it can detect NTD with 95% sensitivity and 92% specificity (AUC: 1.00, p<0.001). Conclusion: Salivary and serum AFP values showed strong positive correlation between themselves. We believe that saliva can be used in NTD screening performed by AFP measurement.