Results
The ages of patients were similar between the groups (p:0.503). However, the groups were determined to be statistically different in regards to gravidity and parity (p<0.05). The comparison of the blood parameters between the groups revealed that the fibrinogen (mg/dl), albumin (g/dl), FAR (%), NLR (%), RDW CV (%), RDW SD (fL), and platelet counts (10-3/ uL) were statistically different between the groups (p<0.05). The MPV (fL) and D-dimer (ug/L) were measured in similar ranges between the groups (p>0.05). Especially, higher fibrinogen, FAR, NLR and platelet count values were obtained for the RPL group. Unlikely, higher albumin, RDW CV and RDW SD values were obtained for the control group. A comparison between the demographical samples and the blood sample variables is summarized in Table 1.
The gravidity was significantly different when the RPL subgroups were compared (p:0.731). Other parameters were determined to be statistically similar when the variables were compared with respect to abortion in the RPL group (p>0.05). A moderate positive correlation was observed between gravidity count and abortion count when evaluated with the Kendall tau-b correlation coefficient (p<0.01; b=0.544). A comparison of variables according to abortion in the RPL group is presented in Table 2.
Higher FAR levels above the reference lines were observed in the ROC curve analysis (Figure 1). A cut-off point of 105.69% was selected to predict abortion risk with 79.5% sensitivity and 88.3% specificity (AUC: 0.877, 95% CI: 0.806-0.949). Additionally, the NLR levels were 84.1% sensitive and 75% specific for predicting RPL with a cut-off value of 4.27%. The ROC curve analysis of the NLR and FAR values are presented in Figure 1.
DiscussionAlthough the prothrombotic gene panel or some inflammatory markers were investigated in previous studies of patients with RPL, the routine blood parameters were not compared comprehensively. Our results indicated that the serum fibrinogen, albumin, RDW, NLR, and FAR values can be related to RPL. According to our knowledge, this analysis is the first study that determines a cut-off FAR value for specifying RPL. Moreover, the serum NLR and FAR levels were determined to be quite sensitive for identifying RPL risk.
RPL is an important female reproductive disorder that is related with multifactorial etiology. The anatomic, endocrine, infection, immune and thrombophilic factors are the main reported etiologies for this disorder [1, 8]. Although RPL is a challenging disease, note that a successful pregnancy may be achieved by comprehensive management for etiological factors [1]. Especially, the inflammation and coagulation disorders that cause RPL can be more easily explained and managed by clinicians [8]. Previous studies described decidual inflammation, perivillous and decidual fibrin deposition, and thromboembolic changes in decidual vascular structures after immunopathological examination of gestational structures following a spontaneous recurrent abortion in RPL cases [8]. Higher cytokine levels, such as mononuclear cells secreted from TNF-a, IFN-g, TNF-b, and IL-2 and increased inflammatory response, were detected in RPL patients when compared with normal pregnancy [8, 9]. Incremental neutrophil and leukocyte counts were reported from the first trimester to the third trimester in non-complicated pregnancy cases, and conversely, decremental lymphocyte counts were identified from the first trimester to the second trimester [10]. Therefore, the NLR was investigated as a predictive marker for pathologic gestational events [11,12,13,14,15]. The NLR is the current concerted version as a predictor for inflammatory disorders, is especially investigated in atherosclerotic, thrombotic, and/or immune vascular events and is suggested as a potentially useful biomarker for prediction and follow-up for inflammatory processes [7, 16]. Gezer et al. investigated NLR values in determining the predictive value of subsequent preeclampsia. According to their report, a higher value of NLR (with a cut-off value of NLR ≥3.08) can be associated with an increase in subsequent preeclampsia risk [11]. Similarly, Serin et al. reported higher NLR values in patients with preeclampsia compared with normal controls [12]. In another clinical study, Ilhan et al. evaluated the diagnostic accuracy of NLR in premature ovarian insufficiency. They reported similarities between serum NLR levels and ovarian reserve markers, such as follicle stimulating hormone and anti-müllerian hormone levels. According to the findings, these researchers claimed that the NLR can be a potential diagnostic marker for ovarian insufficiency [13]. There are limited data about NLR levels and the relation with miscarriage. Karakus et al. investigated NLR values in vaginal bleeding related to ectopic pregnancy or miscarriage cases. They obtained higher NLR values in miscarriage patients and suggested that the NLR can be employed as an early diagnostic marker for miscarriage in the absence of infection [14]. A conflict report was presented by Christoforaki et al. with a retrospective analysis that revealed similarly distributed NLR values in failed or successful pregnancies. They suggested that “it is not possible to select a single NLR value that will split failed and successful pregnancies with reasonable sensitivity and specificity.” [15]. We obtained markedly higher NLR levels in patients with RPL.
The RDW is a numerical indicator of the variation in the size of circulating erythrocytes and is routinely applied in the differential diagnosis of anemia. The RDW was suggested as a significant and independent predictor of pathological conditions in community scanning [17]. Although the RDW is a conventionally accepted routine marker in the group of complete blood counting parameters, the reference ranges for pregnancy were not well established. In a systematic review, RDW values were suggested as possible markers for diagnostic and prognostic use in clinical practice for pregnancy complications, including anemia, preeclampsia, diabetes, and recurrent miscarriage [18]. We found relatively higher RDW levels in RPL cases when compared with control group. However, this difference is not statistically strong for the NLR and FAR values. In gene polymorphism studies, prothrombotic gene mutations were determined to be the etiological reason for RPL. Jeddi-Tehrani beta fibrinogen and methylenetetrahydrofolate reductase gene polymorphisms were positively associated with RPL [19]. Factor V Leiden, plasminogen activated inhibitor gene mutations and elevated fibrinolytic activity and platelet levels are described in recurrent miscarriage and related disorders [20]. Additionally gene groups that regulate platelet functions were examined in RPL cases [21]. Karami et al. suggested that the polymorphism of these gene groups can trigger platelet activation and thrombosis and disrupt placental blood diffusion. They added that the enhanced platelet activation and triggered thrombosis formation can also be attributed to RPL [21]. The routine blood parameters that indicate platelet functions were also investigated and compared in RPL and normal gestation cases. Aynıoglu et al. reported higher platelet counts and MPV levels in the RPL population. They claimed that these values have a predictive role for RPL risk [22]. We obtained higher platelet counts in RPL cases but did not observe a difference between RPL cases and normal cases in regards to MPV levels. Because of previously reported decidual fibrin deposition on the histopathologic examination of the placenta in miscarriage cases and increased fibrinolytic activity, we investigated fibrinogen and D-dimer levels in RPL. We observed markedly higher fibrinogen levels in RPL patients. However, D-dimer levels were found as similar with normal gestation group. In recent cardiovascular studies, the FAR was utilized as a predictive marker for venous and arterial disorders [23,24]. These previous studies claimed that blood viscosity and oncotic pressure can be affected by fibrinogen and albumin and contribute to the development of vascular thrombosis and insufficient perfusion [23,24]. Similarly, we obtained higher FAR levels in RPL cases compared with the normal gestation group.
In addition, Covid-19 pandemic is a current and serious health problem [25]. Several studies conducted over the past one year have revealed that Covid-19 cases showed significantly higher plasma levels of fibrinogen and D-dimer than healthy controls, and significant hypercoagulation was observed in Covid-19 patients [25]. Since we reached a conclusion that recurrent pregnancy loss is associated with hypercoagulability in our work, further studies are needed to determine whether Covid-19 is related to pregnancy loss or not.