Correlation of calprotectin serum levels with degrees of endometriosis: A cross-sectional study

Abstract Background Endometriosis is closely associated with delayed diagnosis due to the lack of a definitive and sensitive noninvasive approach. The use of calprotectin in inflammatory process has been demonstrated in various inflammatory diseases. Calprotectin has a significant correlation with high-sensitivity C-reactive protein (hs-CRP) and could be used as an inflammatory marker. No study thus far has evaluated the correlation between calprotectin and endometriosis. Objective To determine the correlation of calprotectin with the degree of endometriosis in order to help clinicians in establishing better early detection and management. Materials and Methods In this cross-sectional study, 46 women referred to the Cipto Mangunkusumo, Fatmawati, and Persahabatan Hospitals in Jakarta, Indonesia between July 2017 and April 2018 were enrolled, and their blood serum were taken a day before surgery. Calprotectin serum level was treated using the PhicalⓇ ELISA method. After the diagnosis of endometriosis was confirmed through pathological examination, the final diagnosis of endometriosis could be established. The degree of endometriosis was classified according to the revised American Society for Reproductive Medicine (ASRM) classification. Results The prevalence of minimal, mild, moderate, and severe degrees of endometriosis were 15.2, 39.1, 34.8, and 10.9%, respectively. The median serum calprotectin levels for minimal, mild, moderate, and severe endometriosis were 138.98, 121.49, 124.16, and 122.82 mg/mL, respectively. No correlation was observed between calprotectin and the degrees of endometriosis (r = –0.16, p = 0.278). Conclusion There is no correlation between calprotectin serum levels and the degrees of endometriosis.


Introduction
Endometriosis is generally associated with decreased quality of life in patients due to the prolonged and cyclic pain. The symptoms are usually associated with menstruation and chronic pelvic pain (1). Other problems include late diagnosis and the time of endometriosis therapy (around -12 yr) (2). There is no definitive and sensitive noninvasive approach or biomarkers for the early diagnosis of the disease (3).
The incidence of endometriosis is difficult to measure, some of these women are often asymptomatic and the imaging modalities have a low sensitivity. Its prevalence among reproductive-age women is between 5 and 10% (4), with an asymptomatic prevalence ranging from 2 to 22% (5). There is no accurate diagnostic method other than looking directly into the pelvis (laparoscopy) and ascertaining it by anatomic pathological examination (6). Inflammation and immune response play an important role in the development of endometriosis; chronic inflammation causes the development of endometrial ectopic tissue growth, influences the immune system, which is related to angiogenesis, lymphangiogenesis, and neurogenesis (7).
Calprotectin is released from neutrophils and monocytes during their activation, and increased systemic levels of the protein have been linked with increased immunological activity and inflammation (8). The use of calprotectin has been demonstrated in various inflammatory diseases, it has the advantage of being stable at room temperature. In addition to serum, calprotectin levels can also be measured in body fluids such as saliva, synovial fluid, or feces (9).
Calprotectin has been reported to be correlated with serum high-sensitivity C-reactive protein (hs-CRP) levels, which supports the hypothesis that it could be used as an inflammatory marker (10). To the best of our knowledge, no study has ever examined the relationship between the levels of calprotectin and endometriosis.

Materials and Methods
This study was conducted at the Cipto

Statistical analysis
This study used an observational analysis with a cross-sectional design. The sample calculation was done by using formula suitable for the correlative analytics (11). Alpha standard deviation was set at 5%, with a positive two-way

Results
Blood serum samples were taken from a total of 46 subjects a day before their surgery and the results of pathology anatomy and surgical findings

Discussion
Chronic inflammation and immune response play a role in the endometriosis development. shows that calprotectin could be used as an inflammatory marker (r = 0.510, p < 0.001) (10). Another study reported the advantage of calprotectin being stable at room temperature.
Calprotectin is a good candidate to monitor activity and the degree of the disease. In addition to serum, calprotectin levels can also be measured in body fluids such as saliva, synovial fluid, or feces. Another advantage of serum calprotectin is that it is stable and easily measured compared to other cytokines, so that calprotectin has the potential to be a good biomarker of inflammatory diseases (9). Calprotectin was also reported as a marker that could be used to monitor the active stage of the rheumatoid arthritis (RA) disease, which is a chronic inflammatory disease of joints. Calprotectin is secreted locally during the inflammatory process and its concentration increases in joint fluid and is also associated with the degree of the disease.
It is also said that calprotectin is superior to Calprotectin is a calcium-binding protein which belongs to the S100/calgranulins group.
It is a heterodimer of two calcium-binding proteins, that are, S100A9 and S100A8 (14,15 (16). Calprotectin binds to TLR4 which can explain inflammation and infection (17). S100A8 and S100A9 form complex (calprotectin) that triggers the TLR4-signaling pathway, which in turn increases the proinflammatory cytokines production, including the Interleukin 1β (IL-1β), which then activates monocytes and neutrophils.
This activation increases the secretion of S100 proteins (S100A8 and S100A9) so that the calprotectin production also increases and so on (18

Conclusion
No correlation was found between calprotectin serum levels and the degrees of endometriosis.
Further studies need to be done to examine the correlation between fecal and peritoneal fluid calprotectin as a marker of local inflammation with the degrees of endometriosis.