Pentraxin-3 is a novel marker for the diagnosis of endometriosis

Abstract

Introduction:

Endometriosis is one of the most common reproductive disorders affecting women. The pathophysiology of endometriosis is also quite complicated, and many mechanisms have been put forward. Pentraxin-3 is a glycoprotein released by leukocyte and myeloid dendritic cells in peripheral blood with the stimulation of some cytokines, especially IL-1 and TNF-α, Toll-Like Receptor agonists, or microbial components. It has been shown that pentraxin-3 is also released from ectopic endometrial cells. The aim of this study is to investigate serum pentraxin-3 levels and their correlation with endometriosis in women with endometriosis and healthy women without endometriosis.

Methods:

This case-control study evaluated patients diagnosed with endometriosis based on imaging techniques or laparoscopy between 2018 and 2020. Serum samples of 71 patients who had been diagnosed with endometriosis as a case group and 56 healthy patients who had undergone laparoscopic tubal ligation and were proven to be endometriosis-free as a control group were compared for pentraxin-3 level.

Results:

Serum pentraxin-3 level was significantly higher in the endometriosis group compared with the control group (p < 0.05). Parity and gravida were significantly higher in the control group than in the endometriosis group. When patients with endometriosis surgery history were excluded, there was no significant change in serum pentraxin-3 levels in patients with medical treatment for endometriosis (p > 0.05). Both the sensitivity and specificity of serum pentraxin-3 were 73.2%.

Conclusions:

These results demonstrate a relationship between serum pentraxin-3 and endometriosis. Serum pentraxin-3 might be used as a non-invasive method for the diagnosis of endometriosis.

Keywords

Diagnosis endometriosis pentraxin-3

Introduction

Endometriosis is characterized by the presence of endometrium-like glands and stromal tissue outside the uterus.¹ Endometriosis is mainly found in the pelvic structures; however, more rarely, it can appear anywhere in the body. Endometriosis is one of the most common reproductive disorders affecting women.² The pathophysiology of endometriosis is also quite complicated, and many mechanisms have been put forward especially Sampson’s regurgitation theory.^3–9 Women with endometriosis have elevated levels of cytokines such as Interleukin-1 and Tumor Necrosis Factor-α.¹⁰ These patients also have high estrogen production resistant to progesterone, especially in the endometriotic focus.¹¹

The highest prevalence of endometriosis is reported between 5% and 50% in infertile women. This rate varies between 2% and 18% in asymptomatic patients. This rate is slightly higher in patients with pelvic pain, ranging from 5% to 21%.¹² Although dysmenorrhea, chronic pelvic pain, dyspareunia, painful defecation, and infertility are often encountered symptoms in endometriosis, many cases of endometriosis may be completely asymptomatic. The wide spectrum of clinical signs and symptoms causes difficulties in treatment and diagnosis for clinicians and patients.¹³ In addition, the duration between the onset of the initial symptoms and the diagnosis may be 7–8 years.¹⁴

The fact that non-specific symptoms and findings are distributed in a wide range, and the definitive diagnosis still requires histological sampling, requires non-invasive methods for the diagnosis of endometriosis disease. Pentraxin-3 is a glycoprotein released by leukocyte and myeloid dendritic cells in peripheral blood with the stimulation of some cytokines, especially IL-1 and TNF-α, Toll-Like Receptor agonists, or microbial components. It has been shown that pentraxin-3 is also released from ectopic endometrial cells.^15,16 In this study, we aimed to demonstrate the role of pentraxin-3 in the diagnosis of endometriosis.

Materials and methods

Our prospective case-control study is conducted on women aged 18–50 years to measure serum pentraxin-3 levels in endometriosis patients as a non-invasive diagnostic method. Blood samples were obtained from 71 patients who were hospitalized with the diagnosis of endometriosis and planned for surgery or observation between 2018 and 2020 in the gynecology and infertility units of a tertiary hospital. The diagnosis of endometriosis was confirmed histologically in patients who underwent surgery for endometriosis and/or endometrioma. In patients who required observation for abdominal pain or other symptoms related to endometriosis, the diagnosis of endometriosis was done on the basis of clinical history, ultrasound imaging, and magnetic resonance imaging. The control group comprised 56 fertile women who underwent laparoscopy for tubal ligation and were endometriosis-free. There was no additional disease in both groups. Blood samples of patients undergoing surgery were taken before the operation. Blood samples were collected from both the case group and the control group, and the collected blood samples were centrifuged at 1000 rpm for 20 min and stored in the hospital laboratory in a −80°C cabinet, with a storage period not exceeding 2–6 months. The results of the operation and the demographic-clinical characteristics of the patients were recorded. Serum pentraxin-3 levels, CA125/CA19-9 levels, age, obstetric history, symptoms, preoperative ultrasonographic findings, preoperative physical examination findings, intraoperative findings, and patients’ pathology results were recorded as primary outcome variables during the study. The results of the case and control group were compared in terms of the pentraxin-3 levels. Exclusion criteria were pregnancy, breastfeeding in the last 6 months, patients with acute inflammatory diseases (such as pelvic inflammatory disease and tubo ovarian abscess), patients with known or suspected infectious disease, patients with chronic autoimmune diseases, and patients with malignant disease.

This study was approved by the clinical research ethics committee of Dr. Zekai Tahir Burak Women’s Health, Training and Research Hospital, Ankara, Turkey (decision number: 13/2018). The study protocol was in compliance with the Declaration of Helsinki, and informed consent was obtained from each participant.

Statistical analysis

There is no exact copy of the previous study. In this context, our study is the first study on the subject. The sample size was calculated using the Medicres E-PICOS program on the basis of a previous study conducted by Ishida et al.¹⁷ Based on their findings, it was estimated that 148 patients would have to be included with 0.05 alpha error and 90% power. Pentraxin-3 levels were determined in the serum samples of the patients in the case and control groups, the demographic-clinical characteristics of both groups and the operation results were compared using the SPSS statistical program, and their statistical significance was evaluated. Descriptive analyses are given using the mean and standard deviations for normally distributed variables. The means of parametric data determined by Levene’s test, which showed normal distribution, were compared using the Student’s T-test. The Mann-Whitney U test was used to compare the parametric and ordinal data, which were determined not to show normal distribution. The existence of a correlation between parametric data was tested using the Pearson test, and the existence of a correlation between non-parametric or non-normally distributed data was tested using the Spearman test. Categorical data were compared using Chi-square or Fisher’s exact test, as appropriate (where values observed in cells do not meet the Chi-square test assumptions). Cases where the p value was below 0.05 were considered statistically significant.

Results

Demographic and clinical characteristics of the study groups have been demonstrated in Table 1. Serum pentraxin-3 levels were found to be significantly higher in the endometriosis group (p < 0.05; Figure 1, Table 1). The correlation between CA125/CA19-9 levels and pentraxin-3 expression in the peripheral blood of women with endometriosis is reported in this study. Spearman’s correlation coefficient showed that the weak negative correlation between the CA125 value and Pentraxin-3 level was not statistically significant (r = -0.173; p > 0.05). A similar interpretation can be made between the CA19-9 level and the pentraxin-3 level. The inverse and weak relationship here is also not statistically significant (r = -0.117; p > 0.05).

Table 1.

Demographic and clinical characteristics of the patients.

	Endometriosis group (n = 71)	Control group (n = 56)	p Value
Pentraxin-3	17.67 ± 19.61	7.38 ± 10.87	<0.05
Age (years)	33.23 ± 7.78	42.75 ± 6.73	<0.05
Gravida	1	3	<0.05
Parity	1	3	<0.05
Abortion	0	0	0.985
Comorbidity
Hypertension	0	1	1
Diabetes mellitus	0	1
Others	2	0
Symptoms
Chronic pelvic pain	39 (54.9%)	0
Dysmenorrhea	45 (63.4%)	0
Dyspareunia	19 (26.8%)	0
Infertility	24 (33.8%)	0
CA 125 (U/ml)	118.95 ± 47.44	21.34 ± 13.2	<0.05
CA 19-9 (U/ml)	149.75 ± 57.39	18.87 ± 6.76	<0.05
Previous medical treatment for endometriosis (months)	3 (1–24)	0	–
Previous abdominal surgery	8 (11.3%)	9 (16%)	0.430

Values are presented as mean ± SD and median (range).

CA 125: Cancer antigen 125; CA 19-9: Carbohydrate antigen 19-9.

The analyses performed by excluding patients who had undergone surgery showed that medical treatment did not cause a statistically significant change in pentraxin-3 levels (p = 0.067). When patients who had undergone surgery were excluded from the analysis, the negative correlation between serum pentraxin-3 level and duration of medical treatment was not statistically significant (r = -0.129; p > 0.05).

The area under the ROC curve was analyzed to estimate the accuracy of pentraxin-3 expression in the peripheral blood to diagnose endometriosis (Figure 2). The most appropriate positive cut-off value for pentraxin-3 value was 4.73 ng/ml, and this was statistically significant (p < 0.05). The area under the curve (AUC) was 0.808 (95% CI = 0.726–0.890, p < 0.05) at the 95% confidence interval. When this value is close to 1 that indicates the diagnostic value is high. The sensitivity of pentraxin-3 level was 73.2%, and the specificity was also 73.2% in the study.

Discussion

Endometriosis is a histologically diagnosed disease affecting 6%–10% of reproductive-aged women. Due to the invasive nature of diagnostic methods, the time lapse between the beginning of the symptoms and diagnosis can be as long as 7–8 years. Although some non-invasive serum markers are suggested as diagnostic tools, their sensitivity and specificity rates were found to be limited.^18–20 In this study, the serum pentraxin-3 level as a non-invasive diagnostic method was investigated in order to reduce the time to diagnosis in the endometriosis group.

Since pentraxin-3 is a relatively newly discovered and researched molecule, our study is one of the pioneering studies in this field. It is a large-scale study compared to other studies in terms of the number of cases included in the study. As a result of our research, the serum pentraxin-3 levels from women with endometriosis were significantly higher than the control group who had not exhibited any stage of endometriosis.

In a study conducted by Ishida et al.¹⁷ in 2016, preoperative and postoperative pentraxin-3 levels of 18 patients with mature cystic teratoma, 18 patients with uterine leiomyoma, and 20 patients with endometrioma were compared. Regarding preoperative and postoperative pentraxin-3 level comparisons, a significant decrease was observed in the mature cystic teratoma group postoperatively but pre and postoperative serum PTX3 levels were similar for the endometrioma group. The pentraxin-3 levels of two patients with endometrioma were higher than the positive cut-off value, which was determined as 3.5 ng/ml. Pentraxin-3 was known to be released from ectopic endometriotic cells. According to their study results, pentraxin-3 levels in patients with endometrioma remained below the threshold. Our study included 71 patients with endometriosis and 56 healthy patients. Compared to the control group, pentraxin-3 levels were found to be significantly high in the case group. In our study, the most appropriate threshold value of pentraxin-3 for the diagnosis of endometriosis was 4.73 ng/ml. At this value, the sensitivity and specificity of the pentraxin-3 level was 73%.

In another study conducted by Wisnumurti et al., the level of serum pentraxin-3, which is obtained from ovarian follicle liquid, was compared among patients who were infertile and had mild, moderate, or advanced endometriosis. Consequently, it has been proven that the higher severity of disease causes the higher levels of pentraxin-3 (correlation analysis between pentraxin-3 level and endometriosis severity rs = 0.943 and p = 0.000). In this study, the level of pentraxin-3 was measured locally, and it was shown that the level was increased in patients with endometriosis.²¹ In our study, it was observed that pentraxin-3 levels measured in peripheral blood were higher in patients with endometriosis compared to the healthy population. Although no significant difference was observed between the duration of medical treatment and the change in serum pentraxin-3 levels (p = 0.06), studies with a larger number of patients are needed.

It should not be forgotten that the circulating levels of pentraxin 3, an acute phase reactant, may be high in patients with inflammatory, infectious, autoimmune, and chronic diseases, including arthritis, infections, systemic lupus erythematosus, rheumatoid arthritis, acute abdominal pain, coronary artery disease, etc.^22–27 In 2023, Octavius et al.²⁴ conducted a meta-analysis including 520 patients, and they showed increased pentraxin-3 levels in patients with acute abdominal pain. The authors found that the combined sensitivity and specificity of serum pentraxin-3 in diagnosing acute appendicitis in patients with abdominal pain are 90.3% and 91.2%, respectively. Although endometriosis does not cause acute pelvic pain, the patient should be questioned about other inflammatory diseases that may increase pentraxin-3 levels.

The literature shows that pentraxin-3 levels increase in viral infections, including COVID-19. A recent study that was presented by Moulana et al.²⁸ reported that patients with COVID-19 had significantly higher levels of PTX3 compared to the healthy control group. PTX3 levels may also increase in people with viral infection during seasonal flu periods.²⁸

This study was not powered to evaluate the effect of medical treatment on serum PTX3 levels among endometriosis patients. This can be stated as a limitation of our study. In addition, the patients with any other disease were excluded from the study. The analysis could be better when three groups (endometriosis group, inflammatory patients without endometriosis group, and control group) were compared. The lack of this analysis can be viewed as another limitation of the study. Further studies are needed to evaluate and confirm the applicability of the PTX3 as a proposed biomarker for non-invasive diagnosis of endometriosis.

Conclusion

Increased expression of the pentraxin-3 in the peripheral blood of women with endometriosis may indicate their role in response to inflammation in ovarian and ectopic endometrial tissue in the development of disease. The findings suggest that pentraxin-3 may be a potential non-invasive biomarker for the diagnosis of endometriosis. Due to being affected by multifactorial mechanisms such as altered immunity and genetic factors, further studies evaluating the disease progress and diagnostic markers may contribute to the management of this chronic inflammatory disease.

Footnotes

Authorship contributions

Concept: I.GA., C.S, and S.K.; Design: I.GA., C.S, A.O.A., and S.K.; Data Collection or Processing: I.G.A., C.S., and A.O.A.; Analysis or Interpretation: B.G., A.O.A., and Y.E.P.; Literature Search: I.G.A., B.G., Y.E.P., and S.K.; Writing: I.G.A., B.G., Y.E.P., and S.K.

Data sharing statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Ethics committee approval

Ethics committee of Dr. Zekai Tahir Burak Women’s Health, Training and Research Hospital, Ankara, Turkey (decision number: 13/2018).

ORCID iDs

Ilayda Gercik Arzik

Burak Giray

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