Statistical tests
Continuous variables were described using mean and standard deviation (SD) or median and interquartile range (IQR). One-way analyses were performed after the Shapiro-Wilk normality test, and independent samples t-tests and Mann-Whitney U tests were used to compare differences between the two groups for parametric and nonparametric variables, respectively. The threshold of statistical significance was set at a p-value < 0.05. All data analyses were performed using R software (https: www.r-project.org, version 4.1.3) and SPSS 21.0 (SPSS Inc., Chicago, IL, USA).
Stepwise logistic regression is used to analyze the independent risk variables for RSA in each group. To evaluate the relationship between TAFI and RSA, binary logistic regression was used, with the normal reference range of TAFI as a reference. The adjusted confounders were the variables screened by the multifactorial regression analysis.
Unconditional logistic regression models were conducted in stratified analysis by age, coagulation indicators, thyroid function indicators. Restricted cubic spline models with four knots were used to explore the potential association between TAFI and RSA under different antibody conditions. The four knots include the TAFI 1st percentile, 24ug/mL, 35ug/mL, and the TAFI 99th percentile.