Fig. 4

Linear regression analysis of optimal cutoff value and 5-year age groups. Through linear regression analysis, the regression coefficient (r, corresponding to the slope of the regression line) was determined (here: 0.23; 95% confidence interval 0.11–0.35). This coefficient represented an increase in the level of D-dimer per 5 years. By dividing the regression coefficient by 5, the annual increase in the level of D-dimer was obtained. In determining the new age-adjusted D-dimer threshold, the calculated coefficient was used as a multiplier for the patient's age