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Poster session V Academic issues, antepartum fetal assessment, genetics, hypertenson, medical-surgical complications, ultrasound-imaging| Volume 204, ISSUE 1, SUPPLEMENT , S320-S321, January 2011

822: Cross sectional study to identify normal ranges for D-Dimers in pregnancy

      Objective

      Venous thromboembolism (VTE) is a major cause of maternal morbidity and mortality. Outside pregnancy D-Dimer levels are used to screen for VTE. This test is ineffectual in pregnancy because D-dimer levels increase progressively from conception until birth. The aim of this cross sectional study was to establish reference ranges for D-Dimer levels during pregnancy and compare these ranges to the normal non-pregnant range using the Bio-pool Auto Dimer assay.

      Study Design

      D-Dimer measurements were carried out on a total of 694 low risk women carrying singleton pregnancy to term. Samples were taken from 164 women in the first trimester, 167 women who were 19-21, 98 women who were 28-36,102 women who were 38-40 and 164 women day two postpartum. Data from a previous study establishing normal (non-pregnant) ranges of D-Dimer using the same assay was compared with data obtained from these pregnant women (

      Evaluation Report: Eight D-Dimer assays for the exclusion of Deep Vein Thrombosis. Medicine and Healthcare products Regulatory Agency MHRA 03088, Nov. 2003, pp 42-46.

      ).

      Results

      Figure 1 shows the relationship between D-dimer levels and gestation. D-Dimer levels peaked in the last two weeks of pregnancy and began to drop again as early as two days postpartum. Analysis of the population distributions shows that the D-Dimer 95th percentile diagnostic cut-off point for normal non-pregnant women (224 ng/ml) is not applicable at any of the pregnancy time-points studied. In fact, by 28 weeks' gestation >95% of the sample population have D-Dimer levels exceeding the normal cut-off values.

      Conclusions

      This study reported new referance ranges for D-Dimers in pregnancy.Using this data and a thorough clinical assessment, it may be possible to eliminate the need for admission and the use of diagnostic imaging in the diagnosis of VTE in pregnancy. Using the 95th percentile as the recommended cut off point; the cut-off values in pregnancy are outlined in Table 1. These results are instrument dependent and applicable only to the Bio-pool Auto-Dimer Assay.
      Tabled 1
      PeriodMedian5th Percentile95th percentile/cut off
      <12 weeks (n=163)10139499
      19-21+6 weeks (n=167)282131628
      28-36+6 weeks (n=98)4752251033
      38-40+6 weeks (n=102)6613431513
      day 2 postpartum4801931746
      ** The recommended non-pregnancy D-Dimer cut-off level for the Bio-pool Auto-Dimer Assay is 224 ng/ml.(

      Evaluation Report: Eight D-Dimer assays for the exclusion of Deep Vein Thrombosis. Medicine and Healthcare products Regulatory Agency MHRA 03088, Nov. 2003, pp 42-46.

      )

      Reference

      1. Evaluation Report: Eight D-Dimer assays for the exclusion of Deep Vein Thrombosis. Medicine and Healthcare products Regulatory Agency MHRA 03088, Nov. 2003, pp 42-46.