Results of a Chinese study examining the optimal D-dimer cutoff value for predicting pulmonary embolism among women who have undergone cesarean section was recently published in the journal BMC Pulmonary Medicine.

The incidence of pulmonary embolism (PE) is high among postpartum women who have undergone cesarean section, with the diagnostic sensitivity of the traditional D-dimer cutoff value shown to be distinctly reduced in this patient population. The current study sought to optimize the clinical D-dimer threshold, in order to improve specificity while guaranteeing high sensitivity, and to identify risk factors for PE following cesarean section.  

The retrospective analysis was conducted between January 2010 and January 2021 among women at the Shengjing Hospital of China Medical University (Liaoning, China) with suspected PE following cesarean delivery. A total of 125 women who had received diagnostic imaging (ventilation/perfusion) or computed tomographic pulmonary angiography (CTPA) for possible PE after undergoing cesarean delivery were included in the analysis after meeting the study inclusion criteria. Laboratory indicators, including D-dimer levels, and clinical data within 24 hours’ postpartum were obtained from the participants. Among the study participants, 33 were ultimately diagnosed with acute PE (incidence, 11.42%; 95% CI, 7.7-15.1).


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Based on clinical and laboratory indicators 24 hours after cesarean section, 30 patients were included in the PE group (mean age, 31.27±5.29 years; range, 22 to 43 years) and 95 were included in the non-PE group (mean age, 31.62±5.07 years; range, 21 to 43 years), with no statistically significant difference in age reported between the 2 groups.

In the 2 groups of women, the main clinical symptoms included chest distress and tachypnea (37 patients), dyspnea (36 patients), hypoxemia (26 patients), chest pain (15 patients), hemoptysis (5 patients), syncope (3 patients), cardiac/respiratory arrest (2 patients), and sudden death (1 patient). Overall, symptoms of suspected PE appeared on the first day following cesarean section (62.07%), with a median time to onset of 1 day after delivery (range, 1 to 7 days).

In 90.4% (113 of 125) of the women who were evaluated following cesarean delivery, the D-dimer level exceeded the upper limit of the normal reference value (500 ng/mL). When the D-dimer cut-off value was set at 500 ng/mL, the sensitivity and negative predictive value (NPV) were 100.00%, with a specificity of 13.68% and a positive predictive value (PPV) of 26.80%. In contrast, when the cut-off value was adjusted to 800 ng/mL, the specificity increased to 25.26% and the PPV increased to 29.70%; the sensitivity and NPV, however, were maintained at 100.00%. Further, when the cut-off value was adjusted to 1000 ng/mL, the specificity increased to 34.74% and the PPV increased to 31.90%; however, the sensitivity and NPV decreased (to 96.67% and 97.10%, respectively).The reliability of  the cut-off value of 800 ng/mL was confirmed by internal cross-validation, with both a sensitivity and an NPV of 100.00%.

In assessing related risk factors, investigators found that the rate of known thrombophilia was significantly higher among women with PE than in those without PE (33.33% vs 12.63%, respectively; P =.014). No additional risk factors for PE were reported among the patients.

The investigators concluded that the use of a D-dimer cutoff value of 800 ng/mL ensures high sensitivity and increased specificity compared with use of the conventional threshold of 500 ng/mL. The utilization of this higher threshold can help to reduce the number of unnecessary CT scans and thus unnecessary radiation exposure among women following cesarean delivery.

Investigators also stressed that “D-dimer detection within 24 hours after cesarean section in women with suspected PE is necessary,” noting that no prior study has evaluated the D-dimer cutoff value for PE diagnosis within 24 hours after cesarean section.

Reference  

Zhang L, Chen Y, Liu W, et al. Predictive value of D-dimer and analysis of risk factors in pregnant women with suspected pulmonary embolism after cesarean section. BMC Pulm Med. 2021;21:391. doi:10.1186/s12890-021-01757-3