2.6 Statistical analyses:
Shapiro-Wilk tests were used to assess data normality. Maternal GCF-PLAP concentrations were not normally distributed; therefore, non-parametric tests were used to assess statistical differences. Comparisons between proportions were performed with a chi-squared or Fisher’s exact test, and the Mann-Whitney U test was used to compare continuous variables. The association strength was assessed by using a multiple logistic regression model, which was adjusted by systolic blood pressure and PLAP-GCF concentrations. Receiver Operating Characteristic (ROC) curves summarized the classification performance of biomarkers. Goodness of fit and internal validation of the model were assessed using the Bayesian Information Criterion (BIC) and bootstrapping. The statistical analysis was performed using a commercially available software package (STATA software, StataCorp version 14.1, Lakeway Drive College Station, TX, USA). A p < 0.05 was considered statistically significant.