Objective
The pathogenesis of endometriosis is associated with an inflammatory process. Here, we assessed if the levels of high-sensitivity C-reactive protein (hs-CRP) in serum could constitute an effective method for detecting systemic inflammation during endometriosis.
Study Design
This was a prospective, laboratory-based study, which was carried out in a tertiary care university hospital. Patients with histologically proven endometriosis (n = 370) and unaffected women (n = 464) were enrolled from January 2005 through December 2009. We performed complete surgical excision of endometriotic lesions with pathological analysis. In addition, hs-CRP levels were determined through a particle-enhanced immunoturbidimetric method. The hs-CRP levels were measured in both controls and women with endometriosis according to the established surgical classifications of endometriosis: superficial peritoneal endometriosis, endometrioma, and deep infiltration endometriosis. Also, hs-CRP levels were evaluated according to hormonal treatment and menstrual cycle.
Results
The hs-CRP serum levels did not statistically differ between women with endometriosis and controls (median in ng/mL [range]: 0.82 [0.04–42.89] vs 0.9 [0.03–43.73], respectively; P = .599). Moreover, subgroup analysis revealed no difference among superficial peritoneal endometriosis, endometrioma, deep infiltration endometriosis, and controls: 0.8 (0.15–13.35), 0.81 (0.04–38.82), 0.83 (0.09–42.89), and 0.9 (0.03–43.73), respectively; P = .872. Furthermore, no effect was observed regarding hormonal treatment or menstrual cycle.
Conclusion
Although endometriosis is an inflammatory disease, we failed to identify any systemic changes in hs-CRP serum levels. Therefore, hs-CRP analysis appears to be irrelevant to the diagnosis and staging of endometriosis.
Endometriosis is a benign, estrogen-dependent, chronic disease affecting 10% of women of reproductive age. It is characterized by the presence of endometrial-like tissue outside the uterus. The most common clinical features of this condition are pelvic pain and/or infertility. The gold standard for conclusive diagnosis of endometriosis is laparoscopy with histologic confirmation. However, these procedures can delay diagnosis (6-9 years), and require ≥5 physician visits before final determination and/or referral. Notably, the severity of endometriosis is graded in relation to the anatomical extension of the lesions following the revised American Society for Reproductive Medicine (ASRM) classification or according to a recently published surgical classification (superficial peritoneal endometriosis [SUP], endometrioma [OMA], and deep infiltration endometriosis [DIE]).
Evaluation of the exact nature and extension of endometriotic lesions is essential for effective disease management. In the case of surgical management, a precise preoperative evaluation of the disease is necessary for planning adequate surgical intervention and for patient referral to appropriate tertiary care centers specialized in endometriosis. Over 100 endometriosis-associated biomarkers have been investigated as possible markers of pathogenesis and/or severity of the disease. However, the pathogenesis of endometriosis remains ill defined.
The onset and progression of endometriosis is believed to occur through a complex series of events, involving the attachment of endometrial tissue to the peritoneal surface, invasion, progressive estrogen-dependent proliferation, vasculogenesis, and angiogenesis. Moreover, chronic inflammation is considered to play a crucial role in these various steps, contributing to progression of the disease and its clinical symptoms. In fact, a considerable amount of evidence indicates that inflammatory mediators and immunocompetent cells control the development of endometriosis. Many studies have reported that women with endometriosis show increased levels of inflammation-related factors, such as cytokines (interleukin [IL]-6, IL-8, and IL-33; monocyte chemotactic protein-1) and tumor necrosis factor-α. In clinical practice, these biomarkers are not easily measured and cannot be used routinely. In contrast, C-reactive protein (CRP), a member of the pentraxin protein family, is a useful biomarker for detecting inflammation. Indeed, CRP increases during inflammation and can be routinely measured in peripheral blood using either a classic method or a more recently identified high-sensitivity (hs)-CRP technique. In fact, CRP levels have been widely studied in a variety of medical conditions. However, few studies have focused on the potential value of CRP blood serum levels in the assessment of endometriosis. Although hs-CRP measurement was shown to be more accurate than classic CRP analysis in women with endometriosis, the use of hs-CRP in endometriosis remains controversial. In addition, none of the previous studies focused on the utility for diagnosis and/or staging endometriosis of the hs-CRP according to the surgical classification of endometriosis in SUP, OMA, and DIE.
According to the recently modified Quality Assessment of Diagnostic Accuracy Studies (QUADAS) guidelines, we present the largest study assessing hs-CRP levels at a well-defined phase of the menstrual cycle in patients with surgical and histologic classification of endometriotic lesions in SUP, OMA, and DIE compared to surgically investigated controls without endometriosis. The overall aim of our study was to assess the utility of hs-CRP measurement for diagnosis and/or staging of endometriosis according to surgical definition.
Materials and Methods
Patients
The local ethics committee (Comité Consultative de Protection des Personnes dans la Recherche Biomédicale) of our institution approved the study protocol. Also, informed written consent was obtained from all patients. We conducted a prospective laboratory study from January 2005 through December 2009. The initial study population consisted of 1439 nonpregnant patients <42 years old who underwent pelvic surgery.
Women were allocated to 2 groups according to the surgical findings: the endometriosis group consisted of subjects with both surgical exploration and histologically proven endometriosis, and the control group of women without any macroscopic endometriotic lesion, as checked during a thorough examination of the abdominopelvic cavity. Thus, patients visually diagnosed with endometriosis were excluded from the study in the absence of histologic confirmation. In positive cases, the extent of endometriosis was staged and scored surgically according to the ASRM classification (overall, implant, and adhesion scores). Based on histologic findings, the endometriotic lesions were classified into 3 groups: SUP, OMA, and DIE. DIE was histologically defined as endometriotic lesions that infiltrates the muscularis propria (bladder, intestine, ureter). In addition, it has been demonstrated that the different types of endometriosis (SUP, OMA, and DIE) are frequently associated ; therefore, patients were arbitrarily assigned to groups corresponding to the most severe (worst) lesion in accordance with a previously described classification system in which the types were ranked from least to most severe: SUP, OMA, and DIE. By definition, DIE lesions were graded from least to most severe as follows: uterosacral ligament(s), vaginal, bladder, intestinal, and ureteral. The patient’s most severe localization was considered for grading.
For each patient, data were collected in surgeon-conducted, face-to-face interviews during the month preceding surgery. For this, we used a previously published structured questionnaire. Briefly, for all patients, we collected general information such as age, gravidity, parity, height, weight, body mass index, presence/duration of infertility, pelvic pain, and use of hormonal treatments. Furthermore, we preoperatively recorded the existence and type of gynecological pain symptoms (dysmenorrhea, deep dyspareunia, noncyclic chronic pelvic pain, gastrointestinal, and/or lower urinary tract). According to a previous study, noncyclic chronic pelvic pain was defined as intermittent or permanent pelvic pain not related to the menstrual cycle. Also, pain intensity was evaluated preoperatively using a 10-cm visual analog scale (VAS). A pain symptom was denoted as moderate if VAS was <7 or severe if VAS was ≥7.
Collection of serum and the hs-CRP assay
Patients did not report any infectious or inflammatory diseases at the time of serum collection, samples were acquired and analyzed before surgical intervention. Briefly, a peripheral venous catheter was inserted, and 5-10 mL of venous blood was collected into an appropriate Vacutainer Tube (Becton Dickinson, Franklin Lakes, NJ). The blood samples were centrifuged at 3500 g , and serum supernatants were collected. CRP levels were assayed on fresh serum using the hs-CRP method, which was performed on a Cobas Integra 400 Plus analyzer using a particle-enhanced immunoturbidimetric technique (Roche Diagnostics, Mannheim, Germany). The lower detection limit of the hs-CRP assay was 0.03 mg/L, and the functional sensitivity of the hs-CRP assay was 0.11 mg/L. Notably, the hs-CRP measurements were all performed in the same laboratory (G. Bijaoui, MD, Laboratoire Port Royal, Paris, France).
Statistical analysis
All data were computed in a database and then analyzed with software (SPSS; SPSS Inc, IBM Corp, Armonk, NY). Continuous data are presented as means with SD. Student t test and Pearson χ 2 test were carried out for quantitative variables and qualitative variables, respectively. Considering the non-gaussian distribution of hs-CRP measurements, the differences in hs-CRP levels between women with endometriosis and the control group were evaluated using the Mann–Whitney test. When >2 groups were compared, we used the Kruskal-Wallis test ( P < .05), and pairwise comparisons were performed using Dunn multiple comparison test. A P value < .05 was considered statistically significant.
Results
As shown in the Figure , 1439 nonpregnant women <42 years of age were initially included in the study. Among them, 133 refused to participate and the remaining 1306 signed the informed consent. We visualized macroscopic endometriotic lesions in 798 of these patients. Of the 508 remaining patients, who underwent surgery for benign gynecological conditions, 464 were considered as the control group (44 were excluded due to missing serum). Finally, after exclusion of 21 women for incomplete surgical exeresis of endometriosis lesions, 86 women without histologic proof of endometriosis, and 321 women without serum, the endometriosis group ultimately included 370 women.
Patient characteristics are summarized in Table 1 . For the most part, the general features of the patients were similar between the 2 groups; however, women in the study group had a slightly lower body mass index, gravidity, and parity. In addition, it must be noted that patients from the control group had undergone surgeries for various reasons, including ovarian cysts (n = 117), tubal defects (n = 81), fibroids (n = 172), and other benign conditions (n = 94) ( Figure ).
| Patient characteristic | Endometriosis (n = 370) | Control (n = 464) | P value |
|---|---|---|---|
| Age, y a | 31.9 ± 5.3 | 32.2 ± 5.8 | .558 g |
| Height, cm a | 164.8 ± 8.1 | 164.9 ± 7.8 | .773 g |
| Weight, kg a | 59.8 ± 10.5 | 62.8 ± 11.6 | < .001 g |
| Body mass index, kg/m 2 a | 21.9 ± 3.6 | 23 ± 4.1 | < .001 g |
| Parity a | 0.3 ± 0.6 | 0.5 ± 1 | .001 g |
| Gravidity a | 0.6 ± 1.1 | 0.9 ± 1.4 | < .001 g |
| Infertility, n (%) | 120 (32.4) | 142 (30.6) | .688 g |
| Since, mo a | 45.3 ± 33.7 | 43.7 ± 31.2 | |
| Previous treatment for endometriosis, n (%) | |||
| Surgery | 154 (41.6) | NA | |
| Endometrioma surgery | 70 (18.9) | NA | |
| Cycle phase, n (%) | |||
| Under hormonal treatment | 147 (39.7) | 159 (34.2) | |
| Follicular phase | 60 (16.2) | 155 (33.4) | < .001 h |
| Luteal phase | 90 (24.4) | 117 (25.3) | |
| Unknown | 73 (19.7) | 33 (7.1) | |
| Preoperative pain scores a-c | |||
| Dysmenorrhea | 6.7 ± 2.7 | 4 ± 3.3 | < .001 g |
| Deep dyspareunia d | 4.4 ± 3.4 | 2.0 ± 3.0 | .002 g |
| Noncyclic chronic pelvic pain | 3.0 ± 3.1 | 1.8 ± 2.9 | .001 g |
| Gastrointestinal symptoms | 3.6 ± 3.6 | 0.6 ± 1.8 | < .001 g |
| Lower urinary symptoms | 1.0 ± 2.3 | 0.1 ± 1.0 | < .001 g |
| ASRM classification a,e | |||
| Mean implants score ASRM | 16.4 ± 12.3 | NA | |
| Mean adhesions score ASRM | 20.2 ± 24.2 | NA | |
| Mean total score ASRM | 36.4 ± 31.3 | NA | |
| ASRM stage, n (%) e | |||
| I | 50 (13.5) | NA | |
| II | 80 (21.6) | ||
| III | 105 (28.4) | ||
| IV | 135 (36.5) | ||
| Surgical classification | |||
| Superficial endometriosis, n (%) | 41 (11.1) | NA | |
| Endometrioma, n, (%) | 126 (34.1) | NA | |
| Endometrioma size, cm a | |||
| Right | 3.80 ± 2.29 | NA | |
| Left | 4.37 ± 2.84 | NA | |
| Endometrioma laterality, n, (%) | |||
| Bilateral | 29 (7.8) | NA | |
| Right | 37 (10) | NA | |
| Left | 59 (15.9) | NA | |
| DIE lesions, n (%) f | 203 (54.9) | NA | |
| Mean no. of DIE lesions a | 2.82 ± 1.92 | NA | |
| Total no. of DIE lesions, n, (%) | |||
| 1 | 65 (17.6) | NA | |
| 2 | 47 (12.7) | ||
| ≥3 | 91 (24.6) | ||
| Anatomical distribution of DIE, n (%) b,f | |||
| USL | 145 (39.2) | NA | |
| Vagina | 95 (25.7) | ||
| Bladder | 31 (8.4) | ||
| Intestine | 109 (29.5) | ||
| Ureter | 20 (5.4) | ||
| Worst DIE lesion, n, (%) f | |||
| USL | 49 (13.2) | NA | |
| Vagina | 24 (6.5) | ||
| Bladder | 12 (3.2) | ||
| Intestine | 98 (26.5) | ||
| Ureter | 20 (5.4) |
b Sometimes >1 for same patient
d Score according to ASRM classification
e 4% of patients have no sexual intercourse immediately prior to surgery
f According to previously published surgical classification for DIE
The 370 patients of the study group presented 41 (11.1%) histologically proven SUP, 126 (34.1%) histologically proven OMA (right: 37; left: 59; bilateral: 29), and 203 (54.9%) histologically proven DIE. Among the patients presenting with DIE, 65 (17.6%) had 1 lesion, 47 (12.7%) had 2 lesions, and 91 (24.6%) had >3 lesions. Moreover, the patient distribution according to worst DIE lesion was: uterosacral ligament(s) (49 patients, 13.2%), vagina (24 patients, 6.5%), bladder (12 patients, 3.2%), intestine (98 patients, 26.5%), and ureter (20 patients, 5.4%). These 203 patients presented a total of 400 histologically proven lesions, distributed as follows: 145 (39.2%) uterosacral ligament lesions, 95 (25.7%) vaginal lesions, 31 (8.4%) bladder lesions, 109 (29.5%) intestinal lesions, and 20 (5.4%) ureteral lesions ( Figure and Table 1 ). The mean number of DIE lesions per patient was 2.82 ± 1.92. Additionally, the mean preoperative pelvic pain scores for patients are detailed in Table 1 .
The hs-CRP serum levels were measured in all of the 834 women studied, and assay results were reported as median values (in ng/mL) with ranges. However, we failed to identify any difference in serum hs-CRP levels between endometriotic women and controls (study group: 0.82 [0.04–42.89] vs control group: 0.9 [0.03–43.73]; P = .599) ( Table 2 ). Measured hs-CRP values from undetectable to 10 ng/mL were defined as normal. In our study, we observed that 14 (4.9%) women with endometriosis and 18 (3.9%) control patients had hs-CRP levels above the normal threshold. Overall, there was no significant difference between the 2 groups ( P = .920).
| Variable | All phases | Hormonal treatment | Proliferative phase | Secretory phase |
|---|---|---|---|---|
| Controls | 0.9 (0.03–43.73) n = 464 | 0.98 (0.13–38.84) n = 159 | 0.83 (0.12–20.67) n = 155 | 0.90 (0.03–18.32) n = 117 |
| Endometriosis | 0.82 (0.04-42.89) n = 370 | 0.94 (0.9-35.54) n = 147 | 0.65 (0.15-38.82) n = 60 | 0.62 (0.04-14.05) n = 90 |
| P value a | .599 | .839 | .488 | .240 |
According to the previously described surgical classification for endometriosis, we found no difference among patients with median SUP, OMA, DIE, and controls: 0.8 (0.15–13.35), 0.81 (0.04–38.82), 0.83 (0.09–42.89), and 0.9 (0.03–43.73), respectively; P = .872 ( Table 3 ). Also, considering the ASRM classification of endometriosis, we found no difference among patients with stage I–II, patients with stage III–IV, and controls: 0.76 (0.09–35.54), 0.885 (0.04–42.89), and 0.9 (0.03–43.73), respectively; P = .260 ( Table 4 ).
| Variable | All phases | Hormonal treatment | Proliferative phase | Secretory phase |
|---|---|---|---|---|
| Controls | 0.9 (0.03–43.73) n = 464 | 0.98 (0.13–38.84) n = 159 | 0.83 (0.12–20.67) n = 155 | 0.9 (0.03–18.32) n = 117 |
| SUP | 0.8 (0.15–13.35) n = 41 | 1.14 (0.55–9.57) n = 11 | 0.76 (0.21–13.35) n = 8 | 0.55 (0.15–3.21) n = 15 |
| OMA | 0.81 (0.04–38.82) n = 126 | 1.34 (0.2–17.23) n = 38 | 0.65 (0.15–38.82) n = 28 | 0.70 (0.04–6.46) n = 36 |
| DIE | 0.83 (0.09–42.89) n = 203 | 0.85 (0.09–35.54) n = 98 | 0.65 (0.15–11.27) n = 24 | 0.62 (0.11–14.05) n = 39 |
| P value a | .872 | .418 | .875 | .397 |
| Variable | All phases | Hormonal treatment | Proliferative phase | Secretory phase |
|---|---|---|---|---|
| Controls | 0.9 (0.03–43.73) n = 464 | 0.98 (0.13–38.84) n = 159 | 0.83 (0.12–20.67) n = 155 | 0.9 (0.03–18.32) n = 117 |
| Stage I-II | 0.76 (0.09–35.54) n = 130 | 0.91 (0.09–35.54) n = 58 | 0.76 (0.15–13.35) n = 23 | 0.49 (0.15–3.21) n = 31 |
| Stage III-IV | 0.885 (0.04–42.89) n = 198 | 1 (0.14–27.9) n = 89 | 0.65 (0.15–38.82) n = 37 | 0.79 (0.04–14.05) n = 59 |
| P value a | .260 | .960 | .326 | .089 |
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
