Establishment and application of D-dimer reference range in pregnant and postpartum women in Zhejiang Han population

Objective To establish D-dimer normal reference range in pregnant and postpartum women in Zhejiang Han population.Methods Plasma samples were collected from 669 healthy pregnant women, 578 healthy postpartum women, 8 venous thrombosis or DIC patients and 80 healthy non-pregnant women in Women′s Hospital, School of Medicine, Zhejiang University from March 2009 to August 2010.According to different gestational week, postpartum days and delivery pattern, the healthy pregnant and postpartum women were stratified into 3 groups: (1) ≤13 weeks (n=120), 14-20 weeks (n=120), 21-27 weeks (n=145), 28-34 weeks (n=147), ≥35 weeks (n=137);(2) The first day after vaginal delivery (n=163), the second day after vaginal delivery (n=121);(3) The first day after cesarean sections (n=166), the second day after cesarean sections (n=128). These groups were further stratified based on age: ＜30 years old and ≥30 years old.All blood samples were drawn in citrate sodium anticoagulated blood.D-dimer concentration was determined by STA-R Evolution coagulation analyzer.Since D-dimer concentration showed non-normal distribution, the normal values (one-tailed) were established by using (P95) percentile method.The results of 8 patients were used to validate the established normal values.Results In the group of ＜30 years old, the D-dimer values[M(P25-P75)]in group of ≤13 weeks, 14-20 weeks, 21-27 weeks, 28-34 weeks, ≥35 weeks and healthy non-pregnant women were 0.25(0.17-0.37), 0.51(0.38-0.75), 0.75(0.57-1.10), 1.14(0.80-1.48), 1.60(1.14-1.89) and 0.20(0.10-0.28) mg/L, respectively, which showed statistical difference(H=239.24, P＜0.05).In the group of ≥30 years old, the D-dimer values of the above different groups were 0.28(0.14-0.38), 0.50(0.36-0.65), 0.83(0.59-1.41), 0.93(0.68-1.37), 1.47(1.22-1.84) and 0.17(0.12-0.25) mg/L, respectively, which also showed statistical difference(H=127.75, P＜0.05).In the group of ＜30 years old, the D-dimer values were 2.45(1.51-3.77), 1.30(0.97-1.96), 2.68(1.52-3.74) and 1.55(1.10-2.10) on the first and second day after vaginal delivery and cesarean section, respectively, which showed statistical difference (H=64.85,P＜0.05).In the group of ≥30 years old, the corresponding values were 2.20(1.33-3.54), 1.33(1.02-2.14), 2.27(1.66-3.17) and 1.62(1.26-2.69), respectively, which also showed statistical difference(H=18.64, P＜0.05).D-dimer normal values were established based on different gestational week, postpartum days and delivery pattern.The normal values of ≤13 weeks, 14-20 weeks, 21-27 weeks, 28-34 weeks and ≥35 weeks were ≤0.64 mg/L, ≤1.54 mg/L, ≤2.60 mg/L, ≤3.01 mg/L and ≤3.19 mg/L, respectively. The normal values of 1st day after vaginal delivery, 2nd day after vaginal delivery,1st day after cesarean sections and 2nd day after cesarean sections were ≤7.83 mg/L, ≤3.29 mg/L, ≤9.95 mg/L and ≤3.80 mg/L.All 8 patients showed positive results with the above normal values.Conclusion D-dimer normal values in pregnant and postpartum women in Zhejiang Han population are established, which can improve the application values of D-dimer in the pregnant and postpartum population. Key words: Pregnant women; Postpartum period; D-dimer; Reference values; Venous thrombosis; Disseminated intravascular coagulation