Abstract: A noninvasive test for endometriosis would be useful for the early detection of endometriosis in symptomatic women who have pelvic pain and/or subfertility with normal ultrasound results. This would include nearly all cases of minimal-to-mild endometriosis, some cases of moderate-to-severe endometriosis without a clearly visible ovarian endometrioma, and cases with pelvic adhesions and/or other pelvic pathology that might benefit from surgery to improve pelvic pain and/or subfertility. This overview discusses the diagnostic performance of noninvasive or semi-invasive tests for endometriosis, including panels of known peripheral blood biomarkers, protein/peptide markers discovered by proteomics, miRNA, and endometrial nerve fiber density. Tests with high sensitivity and acceptable specificity have been developed; some have been validated in independent populations and are therefore promising. To make real progress, international agreement on biobank development is needed for standard operating procedures for the collection, treatment, storage, and analysis of tissue samples and for detailed clinical phenotyping of these samples. Furthermore, it is necessary to validate the diagnostic accuracy of any promising test prospectively in an independent symptomatic patient population with subfertility and/or pain without clear ultrasound evidence of endometriosis and with a clinical indication for surgery, divided into cases with laparoscopically and histologically confirmed endometriosis and controls with laparoscopically confirmed absence of endometriosis. A noninvasive test for endometriosis would be useful for the early detection of endometriosis in symptomatic women who have pelvic pain and/or subfertility with normal ultrasound results. This would include nearly all cases of minimal-to-mild endometriosis, some cases of moderate-to-severe endometriosis without a clearly visible ovarian endometrioma, and cases with pelvic adhesions and/or other pelvic pathology that might benefit from surgery to improve pelvic pain and/or subfertility. This overview discusses the diagnostic performance of noninvasive or semi-invasive tests for endometriosis, including panels of known peripheral blood biomarkers, protein/peptide markers discovered by proteomics, miRNA, and endometrial nerve fiber density. Tests with high sensitivity and acceptable specificity have been developed; some have been validated in independent populations and are therefore promising. To make real progress, international agreement on biobank development is needed for standard operating procedures for the collection, treatment, storage, and analysis of tissue samples and for detailed clinical phenotyping of these samples. Furthermore, it is necessary to validate the diagnostic accuracy of any promising test prospectively in an independent symptomatic patient population with subfertility and/or pain without clear ultrasound evidence of endometriosis and with a clinical indication for surgery, divided into cases with laparoscopically and histologically confirmed endometriosis and controls with laparoscopically confirmed absence of endometriosis. Discuss: You can discuss this article with its authors and with other ASRM members at http://fertstertforum.com/fassbendera-biomarkers-endometriosis/ Discuss: You can discuss this article with its authors and with other ASRM members at http://fertstertforum.com/fassbendera-biomarkers-endometriosis/ Endometriosis, an estrogen-dependent gynecologic disorder, affects 6% to 10% women of reproductive age from all ethnic and social groups. Endometriosis is defined as the presence of endometrial-like tissue outside the uterine cavity (1Giudice L.C. Kao L.C. Endometriosis.Lancet. 2004; 364: 1789-1799Abstract Full Text Full Text PDF PubMed Scopus (2437) Google Scholar). The degree of endometriosis is staged according to the classification system of the American Society of Reproductive Medicine (2American Society for Reproductive MedicineRevised American Society for Reproductive Medicine classification of endometriosis: 1996.Fertil Steril. 1997; 67: 817-821Abstract Full Text PDF PubMed Scopus (2205) Google Scholar) into minimal, mild, moderate, and severe disease. Endometriosis can be associated with infertility and/or pain symptoms, including cyclic pelvic pain, dysmenorrhea, dyspareunia, dysuria, and dyschezia (3Sinaii N. Plumb K. Cotton L. Lambert A. Kennedy S. Zondervan K. et al.Differences in characteristics among 1,000 women with endometriosis based on extent of disease.Fertil Steril. 2008; 89: 538-545Abstract Full Text Full Text PDF PubMed Scopus (141) Google Scholar, 4Milingos S. Protopapas A. Drakakis P. Liapi A. Loutradis D. Kallipolitis G. et al.Laparoscopic management of patients with endometriosis and chronic pelvic pain.Ann NY Acad Sci. 2003; 997: 269-273Crossref PubMed Scopus (33) Google Scholar). Endometriosis-associated pain can be caused by peritoneal inflammation, adhesion formation, and specific innervation of endometriotic lesions and is correlated with the presence of deep infiltrating disease (5Mechsner S. Schwarz J. Thode J. Loddenkemper C. Salomon D.S. Ebert A.D. Growth-associated protein 43-positive sensory nerve fibers accompanied by immature vessels are located in or near peritoneal endometriotic lesions.Fertil Steril. 2007; 88: 581-587Abstract Full Text Full Text PDF PubMed Scopus (96) Google Scholar, 6Anaf V. Simon P. El Nakadi I. Fayt I. Simonart T. Buxant F. et al.Hyperalgesia, nerve infiltration and nerve growth factor expression in deep adenomyotic nodules, peritoneal and ovarian endometriosis.Hum Reprod. 2002; 17: 1895-1900Crossref PubMed Scopus (245) Google Scholar, 7Wang G. Tokushige N. Markham R. Fraser I.S. Rich innervation of deep infiltrating endometriosis.Hum Reprod. 2009; 24: 827-834Crossref PubMed Scopus (142) Google Scholar, 8Berkley K.J. Rapkin A.J. Papka R.E. The pains of endometriosis.Science. 2005; 308: 1587-1589Crossref PubMed Scopus (333) Google Scholar). Endometriosis can appear as peritoneal lesions, ovarian superficial implants or endometriotic cysts, and/or deeply infiltrative disease with extension to bowel, bladder, and ureter; it is often associated with pelvic adhesions (9Nisolle M. Donnez J. Peritoneal endometriosis, ovarian endometriosis, and adenomyotic nodules of the rectovaginal septum are three different entities.Fertil Steril. 1997; 68: 585-596Abstract Full Text PDF PubMed Scopus (918) Google Scholar). So far, it has not been possible to predict the presence of endometriosis based on symptoms, clinical examination, imaging techniques or blood tests. A symptom-based model study (10Nnoaham K.E. Hummelshoj L. Kennedy S.H. Jenkinson C. Zondervan K.T. Developing symptom-based predictive models of endometriosis as a clinical screening tool: results from a multicenter study.Fertil Steril. 2012; 98: 692-701Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar) has found that menstrual dyschezia and a history of benign ovarian cysts predict both any and stage III–IV endometriosis. Although stage III–IV disease was predicted with a good accuracy (area under the curve [AUC] = 84.9, sensitivity 82.3% and specificity 75.8%), any-stage endometriosis was predicted relatively poorly (AUC = 68.3, sensitivity 84.8% and specificity 43.5%) (10Nnoaham K.E. Hummelshoj L. Kennedy S.H. Jenkinson C. Zondervan K.T. Developing symptom-based predictive models of endometriosis as a clinical screening tool: results from a multicenter study.Fertil Steril. 2012; 98: 692-701Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar). At present, the gold standard for diagnosis of endometriosis is laparoscopic inspection with histologic confirmation after retrieval of lesions (11Kennedy S. Bergqvist A. Chapron C. D'Hooghe T. Dunselman G. Greb R. et al.ESHRE guideline for the diagnosis and treatment of endometriosis.Hum Reprod. 2005; 20: 2698-2704Crossref PubMed Scopus (1172) Google Scholar). However, laparoscopy is a surgical procedure with rare but significant potential risks for the patients (12Slack A. Child T. Lindsey I. Kennedy S. Cunningham C. Mortensen N. et al.Urological and colorectal complications following surgery for rectovaginal endometriosis.BJOG. 2007; 114: 1278-1282Crossref PubMed Scopus (87) Google Scholar). It is interesting that there is no correlation between severity of endometriosis (revised American Fertility Society [AFS] classification) and the type or severity of pain symptoms (11Kennedy S. Bergqvist A. Chapron C. D'Hooghe T. Dunselman G. Greb R. et al.ESHRE guideline for the diagnosis and treatment of endometriosis.Hum Reprod. 2005; 20: 2698-2704Crossref PubMed Scopus (1172) Google Scholar). As endometriosis can be progressive in up to 50% of women (13D'Hooghe T.M. Debrock S. Endometriosis, retrograde menstruation and peritoneal inflammation in women and in baboons.Hum Reprod Update. 2002; 8: 84-88Crossref PubMed Scopus (150) Google Scholar), early noninvasive diagnosis has the potential to offer early treatment and prevent progression. Transvaginal ultrasound (TVU) is an adequate diagnostic method to detect ovarian endometriotic cysts but does not rule out peritoneal endometriosis, endometriosis-associated adhesions (11Kennedy S. Bergqvist A. Chapron C. D'Hooghe T. Dunselman G. Greb R. et al.ESHRE guideline for the diagnosis and treatment of endometriosis.Hum Reprod. 2005; 20: 2698-2704Crossref PubMed Scopus (1172) Google Scholar, 14Moore J. Copley S. Morris J. Lindsell D. Golding S. Kennedy S. A systematic review of the accuracy of ultrasound in the diagnosis of endometriosis.Ultrasound Obstet Gynecol. 2002; 20: 630-634Crossref PubMed Scopus (190) Google Scholar), or some locations of deep infiltrating endometriosis (DIE) (15Dessole S. Farina M. Rubattu G. Cosmi E. Ambrosini G. Nardelli G.B. Sonovaginography is a new technique for assessing rectovaginal endometriosis.Fertil Steril. 2003; 79: 1023-1027Abstract Full Text Full Text PDF PubMed Scopus (103) Google Scholar, 16Bazot M. Thomassin I. Hourani R. Cortez A. Darai E. Diagnostic accuracy of transvaginal sonography for deep pelvic endometriosis.Ultrasound Obstet Gynecol. 2004; 24: 180-185Crossref PubMed Scopus (221) Google Scholar, 17Bazot M. Lafont C. Rouzier R. Roseau G. Thomassin-Naggara I. Darai E. Diagnostic accuracy of physical examination, transvaginal sonography, rectal endoscopic sonography, and magnetic resonance imaging to diagnose deep infiltrating endometriosis.Fertil Steril. 2009; 92: 1825-1833Abstract Full Text Full Text PDF PubMed Scopus (279) Google Scholar). Furthermore, routine vaginal examination alone may be insufficient to detect endometriosis before laparoscopy (18Hudelist G. Ballard K. English J. Wright J. Banerjee S. Mastoroudes H. et al.Transvaginal sonography vs. clinical examination in the preoperative diagnosis of deep infiltrating endometriosis.Ultrasound Obstet Gynecol. 2011; 37: 480-487Crossref PubMed Scopus (119) Google Scholar, 19D'Hooghe T.M. Mihalyi A.M. Simsa P. Kyama C.K. Peeraer K. De Loecker P. et al.Why we need a noninvasive diagnostic test for minimal to mild endometriosis with a high sensitivity.Gynecol Obstet Invest. 2006; 62: 136-138Crossref PubMed Scopus (54) Google Scholar). A noninvasive test would be particularly welcome; recent evidence suggests that significant biologic differences exist between eutopic endometrium from women with and without endometriosis (1Giudice L.C. Kao L.C. Endometriosis.Lancet. 2004; 364: 1789-1799Abstract Full Text Full Text PDF PubMed Scopus (2437) Google Scholar), so this may offer a basis for a semi-invasive diagnostic test based on the analysis of an endometrial biopsy sample. Despite extensive research, no reliable blood tests currently exist for the diagnosis of endometriosis. A biomarker is a measurable “biologic marker” that correlates with a specific outcome or state of the disease (20Kingsmore S.F. Multiplexed protein measurement: technologies and applications of protein and antibody arrays.Nat Rev Drug Discov. 2006; 5: 310-320Crossref PubMed Scopus (587) Google Scholar). The biomarker hypothesis states that changes in levels of analytes, proteins, microRNA (miRNA), genes, or other markers could be a specific characteristic of the disease state (20Kingsmore S.F. Multiplexed protein measurement: technologies and applications of protein and antibody arrays.Nat Rev Drug Discov. 2006; 5: 310-320Crossref PubMed Scopus (587) Google Scholar). Although CA-125, cytokines, and angiogenic and growth factors all show altered levels in the peripheral blood of women with endometriosis when compared with controls (21Othman Eel D. Hornung D. Al-Hendy A. Biomarkers of endometriosis.Expert Opin Med Diagn. 2008; 2: 741-752Crossref PubMed Scopus (16) Google Scholar, 22May K.E. Conduit-Hulbert S.A. Villar J. Kirtley S. Kennedy S.H. Becker C.M. Peripheral biomarkers of endometriosis: a systematic review.Hum Reprod Update. 2010; 00: 1-24Google Scholar), thus far neither a single biomarker nor a panel of biomarkers has been validated for clinical use as a diagnostic test in women with endometriosis (22May K.E. Conduit-Hulbert S.A. Villar J. Kirtley S. Kennedy S.H. Becker C.M. Peripheral biomarkers of endometriosis: a systematic review.Hum Reprod Update. 2010; 00: 1-24Google Scholar, 23Vodolazkaia A. El-Aalamat Y. Popovic D. Mihalyi A. Bossuyt X. Kyama C.M. et al.Evaluation of a panel of 28 biomarkers for the non-invasive diagnosis of endometriosis.Hum Reprod. 2012; 27: 2698-2711Crossref PubMed Scopus (118) Google Scholar). The development of a noninvasive diagnostic test—from initial biomarker discovery to a clinically approved biomarker assay—is a long, difficult, and uncertain process (24Surinova S. Schiess R. Huttenhain R. Cerciello F. Wollscheid B. Aebersold R. On the development of plasma protein biomarkers.J Proteome Res. 2011; 10: 5-16Crossref PubMed Scopus (241) Google Scholar). According to a panel of internationally respected endometriosis experts (25Rogers P.A. D'Hooghe T.M. Fazleabas A. Gargett C.E. Giudice L.C. Montgomery G.W. et al.Priorities for endometriosis research: recommendations from an international consensus workshop.Reprod Sci. 2009; 16: 335-346Crossref PubMed Scopus (227) Google Scholar), the development of a noninvasive diagnostic test for endometriosis is one of the top research priorities. However, researchers and clinicians need to realize that a diagnostic test may do more harm than good by subjecting patients to unnecessary or even potentially harmful procedures (26Evers J.L. Van Steirteghem A.C. All that glistens is not gold.Hum Reprod. 2009; 24: 2972-2973Crossref PubMed Scopus (7) Google Scholar), as the benefits of treating women with asymptomatic endometriosis is unclear (22May K.E. Conduit-Hulbert S.A. Villar J. Kirtley S. Kennedy S.H. Becker C.M. Peripheral biomarkers of endometriosis: a systematic review.Hum Reprod Update. 2010; 00: 1-24Google Scholar). Therefore, we do not recommend the development or use a blood test for screening purposes in asymptomatic women. However, up to 45% of subfertile women, with or without pelvic pain, who have regular cycles, a partner with normal sperm quality, and normal clinical examination and pelvic ultrasound results may have endometriosis (27Meuleman C. Vandenabeele B. Fieuws S. Spiessens C. Timmerman D. D'Hooghe T. High prevalence of endometriosis in infertile women with normal ovulation and normospermic partners.Fertil Steril. 2009; 92: 68-74Abstract Full Text Full Text PDF PubMed Scopus (328) Google Scholar). In the presence of subfertility combined with a history of cyclic or chronic pelvic pain, a clinical examination with positive results for pain, and an ultrasound with positive results for ovarian endometriotic cysts or deep endometriotic nodules, the probability of endometriosis is so high that most gynecologists will offer the patient a laparoscopy combined with excision of all visible endometriotic lesions as well as a histologic examination of at least one implant to confirm the presence of endometrial glands and stroma (19D'Hooghe T.M. Mihalyi A.M. Simsa P. Kyama C.K. Peeraer K. De Loecker P. et al.Why we need a noninvasive diagnostic test for minimal to mild endometriosis with a high sensitivity.Gynecol Obstet Invest. 2006; 62: 136-138Crossref PubMed Scopus (54) Google Scholar). Most gynecologists are not sure whether endometriosis is present when a woman has, for example, subfertility since more than 1 year, a regular cycle, no or limited dysmenorrhea, and a partner with a normal sperm. In addition, if a woman has chronic pelvic pain (requiring at least cyclic or chronic use of pain killers) combined with a normal clinical examination and a normal pelvic ultrasound, many gynecologists remain in doubt about the value of a diagnostic laparoscopy. From a clinical perspective, it is unlikely that these women have moderate-to-severe endometriosis; however, they may have extensive peritoneal endometriosis with or without adhesions associated with subfertility and possibly mild pain (19D'Hooghe T.M. Mihalyi A.M. Simsa P. Kyama C.K. Peeraer K. De Loecker P. et al.Why we need a noninvasive diagnostic test for minimal to mild endometriosis with a high sensitivity.Gynecol Obstet Invest. 2006; 62: 136-138Crossref PubMed Scopus (54) Google Scholar). For this population, a noninvasive or semi-invasive diagnostic test would be useful to discriminate between women without endometriosis (for whom the surgery would be unnecessary) and those with endometriosis, most likely minimal-to-mild disease, who may benefit from surgical therapy for both subfertility and pain and from controlled ovarian stimulation in combination with intrauterine insemination for subfertility (11Kennedy S. Bergqvist A. Chapron C. D'Hooghe T. Dunselman G. Greb R. et al.ESHRE guideline for the diagnosis and treatment of endometriosis.Hum Reprod. 2005; 20: 2698-2704Crossref PubMed Scopus (1172) Google Scholar, 19D'Hooghe T.M. Mihalyi A.M. Simsa P. Kyama C.K. Peeraer K. De Loecker P. et al.Why we need a noninvasive diagnostic test for minimal to mild endometriosis with a high sensitivity.Gynecol Obstet Invest. 2006; 62: 136-138Crossref PubMed Scopus (54) Google Scholar, 28D'Hooghe T.M. Debrock S. Hill J.A. Meuleman C. Endometriosis and subfertility: is the relationship resolved?.Semin Reprod Med. 2003; 21: 243-254Crossref PubMed Scopus (252) Google Scholar). If such a test were also diagnostic for women with pelvic adhesions after previous surgery or after pelvic inflammatory disease (PID), these women would also benefit from surgical laparoscopic adhesiolysis to improve fertility and to reduce pain. In fact, such a test would then be “false positive” for endometriosis but still “true positive” for pelvic adhesions that can be managed by surgery. For the same reasons, such a test would be highly valuable for women or adolescents who do not desire to conceive but have pelvic pain that does not respond well to medical therapy in conjunction with normal clinical examination and pelvic ultrasound results. In summary, a noninvasive test for endometriosis would be useful for women with pelvic pain and/or subfertility with normal ultrasound results. This would include nearly all cases of minimal-to-mild endometriosis, some cases of moderate-to-severe endometriosis without clearly visible ovarian endometrioma, and women with pelvic adhesions and/or other pelvic pathology, who might benefit from surgery to improve their pelvic pain and/or subfertility (19D'Hooghe T.M. Mihalyi A.M. Simsa P. Kyama C.K. Peeraer K. De Loecker P. et al.Why we need a noninvasive diagnostic test for minimal to mild endometriosis with a high sensitivity.Gynecol Obstet Invest. 2006; 62: 136-138Crossref PubMed Scopus (54) Google Scholar). A noninvasive diagnostic test could be developed for serum, plasma, urine, or menstrual fluid that can be recovered from the posterior vaginal fornix or the cervix during speculum examination. A semi-invasive test could be developed for peritoneal fluid obtained via transvaginal ultrasound–guided aspiration or for endometrium obtained via transcervical endometrial biopsy. Whatever method is used, the most important goal of the test is that no women with endometriosis or other significant pelvic pathology are missed who might benefit from surgery (19D'Hooghe T.M. Mihalyi A.M. Simsa P. Kyama C.K. Peeraer K. De Loecker P. et al.Why we need a noninvasive diagnostic test for minimal to mild endometriosis with a high sensitivity.Gynecol Obstet Invest. 2006; 62: 136-138Crossref PubMed Scopus (54) Google Scholar). To achieve this goal, a test with a high sensitivity is needed, which is the probability of a test of being positive when endometriosis is present. In addition, the test needs to have a high specificity, to ensure a high probability of the test being negative when endometriosis is absent. Sensitivity and specificity are statistical measures of performance of a binary classification test, which could be a confounder in data analyses. The predictive value of any diagnostic test is influenced by its sensitivity and specificity as well as the prevalence of the target disease in the population being evaluated. Thus, the predictive value of a diagnostic test includes information about both the test itself and the tested population to give a more useful clinical measure (29Friedland D. Evidence based medicine: a framework for clinical practice. McGraw-Hill, New York1998Google Scholar, 30Sims J.M. Clinical notes on uterine surgery. Robert Hardwicke, London1886Google Scholar). A rule of thumb is that the sensitivity and specificity of a good test should add to at least 1.50, and those of a very good test should add to at least 1.80 (30Sims J.M. Clinical notes on uterine surgery. Robert Hardwicke, London1886Google Scholar, 31Griffith C.S. Grimes D.A. The validity of the postcoital test.Am J Obstet Gynecol. 1990; 162: 615-620Abstract Full Text PDF PubMed Scopus (98) Google Scholar). At present, such a test does not exist. Previous studies have focused on the glycoproteins, inflammatory and noninflammatory cytokines, adhesion molecules, and angiogenic and growth factors that are known to be highly relevant to the pathogenesis of endometriosis and the development of endometriotic lesions. However, neither a single biomarker nor a panel of biomarkers has been validated as a reliable noninvasive test for endometriosis (22May K.E. Conduit-Hulbert S.A. Villar J. Kirtley S. Kennedy S.H. Becker C.M. Peripheral biomarkers of endometriosis: a systematic review.Hum Reprod Update. 2010; 00: 1-24Google Scholar). Cancer antigen 125 (CA-125), the most extensively investigated and widely used peripheral biomarker of endometriosis (32Gupta S. Agarwal A. Sekhon L. Krajcir N. Cocuzza M. Falcone T. Serum and peritoneal abnormalities in endometriosis: potential use as diagnostic markers.Minerva Ginecol. 2006; 58: 527-551PubMed Google Scholar), is produced by endometrial and mesothelial cells and gains entry into the circulation via the endothelial lining of capillaries in response to inflammation (32Gupta S. Agarwal A. Sekhon L. Krajcir N. Cocuzza M. Falcone T. Serum and peritoneal abnormalities in endometriosis: potential use as diagnostic markers.Minerva Ginecol. 2006; 58: 527-551PubMed Google Scholar). However, CA-125 levels in peripheral blood lack diagnostic power as a single biomarker of endometriosis due to low sensitivity (11Kennedy S. Bergqvist A. Chapron C. D'Hooghe T. Dunselman G. Greb R. et al.ESHRE guideline for the diagnosis and treatment of endometriosis.Hum Reprod. 2005; 20: 2698-2704Crossref PubMed Scopus (1172) Google Scholar, 33Mol B.W. Bayram N. Lijmer J.G. Wiegerinck M.A. Bongers M.Y. van der Veen F. et al.The performance of CA-125 measurement in the detection of endometriosis: a meta-analysis.Fertil Steril. 1998; 70: 1101-1108Abstract Full Text Full Text PDF PubMed Scopus (259) Google Scholar). Although previous studies have shown that tumor markers, cytokines, and angiogenic and growth factors show altered levels in peripheral blood (plasma or serum) of women with endometriosis when compared with controls (21Othman Eel D. Hornung D. Al-Hendy A. Biomarkers of endometriosis.Expert Opin Med Diagn. 2008; 2: 741-752Crossref PubMed Scopus (16) Google Scholar, 22May K.E. Conduit-Hulbert S.A. Villar J. Kirtley S. Kennedy S.H. Becker C.M. Peripheral biomarkers of endometriosis: a systematic review.Hum Reprod Update. 2010; 00: 1-24Google Scholar), so far none of them, alone or in combination, have been validated as a noninvasive test for endometriosis (22May K.E. Conduit-Hulbert S.A. Villar J. Kirtley S. Kennedy S.H. Becker C.M. Peripheral biomarkers of endometriosis: a systematic review.Hum Reprod Update. 2010; 00: 1-24Google Scholar), possibly because most studies have included a limited number of patients, limited assessment of different cycle phases and endometriosis stages, a limited number of biomarkers analyzed, limited statistical analysis (mostly univariate statistical analysis only), and have lacked validation in an independent test set of patients. Because of the different types (superficial, deep, cyst) and locations of endometriosis, it is possible that a different subset of biomarkers may be required for the diagnosis of different stages of endometriosis (25Rogers P.A. D'Hooghe T.M. Fazleabas A. Gargett C.E. Giudice L.C. Montgomery G.W. et al.Priorities for endometriosis research: recommendations from an international consensus workshop.Reprod Sci. 2009; 16: 335-346Crossref PubMed Scopus (227) Google Scholar). That is, women with peritoneal endometriosis may have different markers than those with rectovaginal endometriosis (22May K.E. Conduit-Hulbert S.A. Villar J. Kirtley S. Kennedy S.H. Becker C.M. Peripheral biomarkers of endometriosis: a systematic review.Hum Reprod Update. 2010; 00: 1-24Google Scholar). In a study evaluating 28 biomarkers, multivariate analysis of four/five biomarkers—annexin V, vascular endothelial growth factor (VEGF), CA-125, and soluble intercellular adhesion molecule-1 (sICAM-1)/or glycodelin—in plasma samples enabled the diagnosis of endometriosis in women (n = 175) who had disease undetectable by ultrasound with a sensitivity of 81% to 90% and a specificity of 63% to 81% compared with controls who had a laparoscopically confirmed absence of endometriosis (n = 121) (23Vodolazkaia A. El-Aalamat Y. Popovic D. Mihalyi A. Bossuyt X. Kyama C.M. et al.Evaluation of a panel of 28 biomarkers for the non-invasive diagnosis of endometriosis.Hum Reprod. 2012; 27: 2698-2711Crossref PubMed Scopus (118) Google Scholar). These data, which were obtained in a training set and were validated in an independent test set, are therefore promising. The next step is to apply these models for preoperative prediction of endometriosis in an independent set of patients with infertility and/or pain without ultrasound evidence of endometriosis who are scheduled for laparoscopy. It is interesting to look at the biologic relevance of the biomarkers (annexin V, VEGF, CA-125, and sICAM-1/or glycodelin) that performed best in that study, which evaluated 28 biomarkers (23Vodolazkaia A. El-Aalamat Y. Popovic D. Mihalyi A. Bossuyt X. Kyama C.M. et al.Evaluation of a panel of 28 biomarkers for the non-invasive diagnosis of endometriosis.Hum Reprod. 2012; 27: 2698-2711Crossref PubMed Scopus (118) Google Scholar). 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