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.