The ODs in the PF4/heparin EIA depend on the periodontal status in non–heparin-treated individuals. In 3500 individuals of the SHIP cohort the periodontal status (assessed by probing depth) and anti-PF4/heparin Ab EIA ODs for IgG, IgA, and IgM were determined. The individuals were grouped into quintiles according to their mean probing depth. Difference in mean ODs in the anti-PF4/heparin EIA (squares) and 95% CIs are given for quintiles 2 to 5. The individuals in the first quintile were used as reference group. Linear regression models were adjusted for age (5-year categories) and gender (reported as M1 in Table 4). P_trend indicates p for linear trend across quintiles. *P < .05; †P < .01; ‡P < .001 compared with the first quintile. Additional linear regression analyses are given in Table 4.