Endometriosis: advances and controversies in classification, pathogenesis, diagnosis, and treatment

Does Ovarian Endometriosis Increase Oocyte Sensitivity to ICSI-Induced Mechanical Damage?

Some studies have shown that ICSI obtains poorer results than conventional IVF in women with ovarian endometriosis, suggesting that oocytes could be sensitive to ICSI-induced mechanical damage. The aims of this study were to clarify (a) whether ovarian endometriosis could induce peculiar fragility in the oocyte, so that ICSI would finally result harmful, and (b) whether endometrioma removal before IVF could be advisable in order to avoid any hypothetical detrimental effect. We retrospectively studied 368 women, 203 with in situ endometrioma (128 of which underwent ICSI, 75 conventional IVF) and 164 who received laparoscopic stripping of endometrioma before ICSI. For women with in situ endometrioma, cIVF and ICSI outcome was comparable for all parameters studied, including the clinical pregnancy rate per embryo transfer (PR/ET: 31.8% vs. 39.5% in the cIVF and ICSI groups) and cumulative live birth rate per ovum pick-up (CLBR/OPU: 24.4% vs. 27.7%). ICSI outcome was similar comparing women with in situ endometrioma and women previously submitted to laparoscopic stripping of cysts (CLPR/OPU 27.7% vs. 25.3%). Our findings suggest that (a) in women with in situ endometrioma ICSI may be performed, when needed, without harming oocytes and compromising the outcome and (b) that there is no advantage in removing endometrioma before ICSI.

Celecoxib reduces inflammation and angiogenesis in mice with adenomyosis

OBJECTIVE

This study aimed to explore the effect of COX-2 selective inhibitor (celecoxib) on adenomyosis and its mechanism.

METHODS

By establishing a mouse model of adenomyosis and using celecoxib to treat adenomyosis, newly born female mice were randomly divided into a control group, adenomyosis model group, and celecoxib group. Hematoxylin-eosin (H&E) staining was used to observe the depth of endometrial infiltration of mouse adenomyosis. RT-PCR (reverse transcription PCR) and western blot were used to detect the expression of Cyclooxygenase-2 (COX-2), Vascular growth factor (VEGF), Nerve growth factor (NGF), and Corticotropin-releasing hormone (CRH) mRNA and protein in mice before and after celecoxib treatment.

RESULTS

After treatment with celecoxib, the depth of endometrial infiltration of mouse adenomyosis was reduced. COX-2 and VEGF decreased significantly after celecoxib inhibited expression of COX-2 (P<0.001), but there was no significant difference in the expression of NGF or CRH (P>0.05).

CONCLUSION

This study indicated that COX-2 may be an important factor related to the pathogenesis of adenomyosis, and it may become an important molecular target for the treatment of adenomyosis.

Appropriate surgical management of ovarian endometrioma: excision or drainage?

Endometriosis negatively impacts the lives of countless women around the world. When medical management fails to improve quality of life often women are left making a decision whether or not to proceed with surgery. With endometriomas, patient's surgical options include complete surgical removal or drainage via laparoscopy. Here, we review the literature to discuss both techniques, excision and drainage of endometriomas, and what the research supports for endometrioma management.

Immunological Basis of the Endometriosis: The Complement System as a Potential Therapeutic Target

Endometriosis (EM) is a chronic disease characterized by the presence and proliferation of functional endometrial glands and stroma outside the uterine cavity. Ovaries and pelvic peritoneum are the most common locations for endometrial ectopic tissue, followed by deep infiltrating EM sites. The cyclic and recurrent bleeding, the progressive fibrosis and the peritoneal adhesions of ectopic endometrial glands, may cause different symptoms depending on the origin involved. EM is a frequent clinical condition affecting around 10% of women of mainly reproductive age, as well as in post-menopausal women and adolescents, especially with uterine anomalies. The risk of developing EM depends on a complex interaction between genetic, immunological, hormonal, and environmental factors. It is largely considered to arise due to a dysfunction of immunological surveillance. In fact, women with EM exhibit altered functions of peritoneal macrophages, lymphocytes and natural killer cells, as well as levels of inflammatory mediators and growth factors in the peritoneal fluid. In EM patients, peritoneal macrophages are preponderant and highly active compared to healthy women. Peritoneal macrophages are able to regulate the events that determine the production of cytokines, prostaglandins, growth factors and complement components. Several studies have shown alteration in the regulation of the complement activation, leading to chronic inflammation characteristic of EM. Aberrant regulation/activation of the complement system has been observed in the peritoneal cavity of women affected by EM. Thus, complement inhibition may represent a new approach for the treatment of EM, given that a number of complement inhibitors are under pre-clinical and clinical development. Such an intervention may provide a broader therapeutic control of complement-mediated inflammatory damage in EM patients. This review will focus on our current understanding of the role of complement activation in EM and possible modalities available for complement-based therapy.

Biomaterial strategies to replicate gynecological tissue

Properties of native tissue can inspire biomimetic in vitro models of gynecological disease.

EQUSUM: Endometriosis QUality and grading instrument for SUrgical performance: proof of concept study for automatic digital registration and classification scoring for r-ASRM, EFI and Enzian

STUDY QUESTION

Is electronic digital classification/staging of endometriosis by the EQUSUM application more accurate in calculating the scores/stages and is it easier to use compared to non-digital classification?

SUMMARY ANSWER

We developed the first digital visual classification system in endometriosis (EQUSUM). This merges the three currently most frequently used separate endometriosis classification/scoring systems (i.e. revised American Society for Reproductive Medicine (rASRM), Enzian and Endometriosis Fertility Index (EFI)) to allow uniform and adequate classification and registration, which is easy to use. The EQUSUM showed significant improvement in correctly classifying/scoring endometriosis and is more user-friendly compared to non-digital classification.

WHAT IS KNOWN ALREADY

Endometriosis classification is complex and until better classification systems are developed and validated, ideally all women with endometriosis undergoing surgery should have a correct rASRM score and stage, while women with deep endometriosis (DE) should have an Enzian classification and if there is a fertility wish, the EFI score should be calculated.

STUDY DESIGN SIZE DURATION

A prospective endometriosis classification proof of concept study under experts in deep endometriosis was conducted. A comparison was made between currently used non-digital classification formats for endometriosis versus a newly developed digital classification application (EQUSUM).

PARTICIPANTS/MATERIALS SETTING METHODS

A hypothetical operative endometriosis case was created and summarized in both non-digital and digital form. During European endometriosis expert meetings, 45 DE experts were randomly assigned to the classic group versus the digital group to provide a proper classification of this DE case. Each expert was asked to provide the rASRM score and stage, Enzian and EFI score. Twenty classic forms and 20 digital forms were analysed. Questions about the user-friendliness (system usability scale (SUS) and subjective mental effort questionnaire (SMEQ)) of both systems were collected.

MAIN RESULTS AND THE ROLE OF CHANCE

The rASRM stage was scored completely correctly by 10% of the experts in the classic group compared to 75% in the EQUSUM group (P < 0. 01). The rASRM numerical score was calculated correctly by none of the experts in the classic group compared with 70% in the EQUSUM group (P < 0.01). The Enzian score was correct in 60% of the classic group compared to 90% in the EQUSUM group (P = 0.03). EFI scores were calculated correctly in 25% of the classic group versus 85% in the EQUSUM group (P < 0.01). Finally, the usability measured with the SUS was significantly better in the EQUSUM group compared to the classic group: 80.8 ± 11.4 and 61.3 ± 20.5 (P < 0.01). Also the mental effort measured with the SMEQ was significant lower in the EQUSUM group compared to the classic group: 52.1 ± 18.7 and 71.0 ± 29.1 (P = 0.04). Future research should further develop and confirm these initial findings by conducting similar studies with larger study groups, to limit the possible role of chance.

LIMITATIONS REASONS FOR CAUTION

These first results are promising, however it is important to note that this is a preliminary result of experts in DE and needs further testing in daily practice with different types (complex and easy) of endometriosis cases and less experienced gynaecologists in endometriosis surgery.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first time that the rASRM, Enzian and EFI are combined in one web-based application to simplify correct and automatic endometriosis classification/scoring and surgical registration through infographics. Collection of standardized data with the EQUSUM could improve endometriosis reporting and increase the uniformity of scientific output. However, this requires a broad implementation.

STUDY FUNDING/COMPETING INTERESTS

To launch the EQUSUM application, a one-time financial support was provided by Medtronic to cover the implementation cost. No competing interests were declared.

TRIAL REGISTRATION NUMBER

N/A.

Purinergic Signaling in Endometriosis-Associated Pain

Endometriosis is an estrogen-dependent gynecological disease, with an associated chronic inflammatory component, characterized by the presence of endometrial tissue outside the uterine cavity. Its predominant symptom is pain, a condition notably altering the quality of life of women with the disease. This review is intended to exhaustively gather current knowledge on purinergic signaling in endometriosis-associated pain. Altered extracellular ATP hydrolysis, due to changes in ectonucleotidase activity, has been reported in endometriosis; the resulting accumulation of ATP in the endometriotic microenvironment points to sustained activation of nucleotide receptors (P2 receptors) capable of generating a persistent pain message. P2X3 receptor, expressed in sensory neurons, mediates nociceptive, neuropathic, and inflammatory pain, and is enrolled in endometriosis-related pain. Pharmacological inhibition of P2X3 receptor is under evaluation as a pain relief treatment for women with endometriosis. The role of other ATP receptors is also discussed here, e.g., P2X4 and P2X7 receptors, which are involved in inflammatory cell-nerve and microglia-nerve crosstalk, and therefore in inflammatory and neuropathic pain. Adenosine receptors (P1 receptors), by contrast, mainly play antinociceptive and anti-inflammatory roles. Purinome-targeted drugs, including nucleotide receptors and metabolizing enzymes, are potential non-hormonal therapeutic tools for the pharmacological management of endometriosis-related pain.

The role of unfolded protein response in the pathogenesis of endometriosis: contribution of peritoneal fluid

RESEARCH QUESTION

Endoplasmic reticulum stress (ERS) is caused by the accumulation of the misfolded or unfolded proteins in the endoplasmic reticulum and induces the unfolded protein response (UPR). Peritoneal fluid is important in the pathogenesis of endometriosis. In this study, the role of UPR associated with ERS in endometriosis, and peritoneal fluid, were investigated.

DESIGN

Normal, eutopic and ectopic endometrium tissues were divided into menstrual cycle phases, and endometrial stromal cells (ESC) were treated with 10-20% concentration of control peritoneal fluid and peritoneal fluid obtained from women with endometriosis for 10, 30 and 60 min, and 24 and 48 h. The UPR signalling proteins were analysed immunohistochemically and immunocytochemically. Data were compared statistically.

RESULTS

p-IRE1 was increased in ectopic glandular and stromal cells in the early proliferative phase compared with normal and eutopic endometrium. p-PERK increased in ectopic glandular and stromal cells in the late proliferative phase compared with normal endometrium. ATF6 was increased in ectopic glandular epithelium compared with normal endometrium in the proliferative phases, versus eutopic endometrium in the late secretory phase. p-IRE1 and p-PERK were increased in high concentrations of ESC treated with peritoneal fluid obtained from women with endometriosis for 10, 30 and 60 min compared with controls. In ESC treated with peritoneal fluid from women with endometriosis, p-IRE1 decreased at 24-48 h compared with 30 min.

CONCLUSIONS

In endometriosis, UPR pathways are activated as highly dependent on cell type and phase. Also, p-PERK and p-IRE1 increased because of exposure to high-dose peritoneal fluid from women with endometriosis in stromal cells. Our findings provide a basis for further studies searching for a potential biomarker for the diagnosis of endometriosis.

Management of a Thin Endometrium by Hysteroscopic Instillation of Platelet-Rich Plasma Into The Endomyometrial Junction: A Pilot Study

In patients whose embryo transfer has been previously canceled due to a thin endometrium, the injection of platelet-rich plasma (PRP) guided by hysteroscopy into the endomyometrial junction improves endometrial thickness and vascularity. This may well serve as a novel approach for the management of these patients. In this study, 32 patients aged between 27 and 39 years, suffering from primary or secondary infertility, were selected for hysteroscopic instillation of PRP. This cross-sectional study included a retrospective assessment of the improvement of endometrial thickness (>7 mm) on the commencement of progesterone treatment in 24 of 32 patients (75%) after hysteroscopy-guided injections of PRP into the subendometrial zone. After PRP instillation, the endometrium was 7 mm or thicker in 24 of 32 patients, and all 24 patients underwent frozen embryo transfer. Moreover, 12 of 24 patients who underwent embryo transfer conceived, whereas 10 had a clinical pregnancy with visualization of cardiac activity at 6 weeks and two had a biochemical pregnancy. Our approach of PRP injection into the subendometrial region is consistent with the histologically proven regeneration of the endometrium from the endomyometrial junction. We observed an improvement of endometrial thickness and higher pregnancy rates in cases of previously canceled embryo transfer due to a thin endometrium.

Association of TNF-α gene T-1031C polymorphism with endometriosis: A meta-analysis

The single nucleotide polymorphism T-1031C has shown to have an important role in the regulation and transcription efficiency of TNF-α gene. Yet, the relationship between TNF-α T-1031C gene polymorphism and the development of endometriosis (EM) still remains unclear. The aim of this meta-analysis was to summarize the effects of TNF-α T-1031C gene polymorphism and clarify their possible association with EM. A comprehensive literature search was performed using PubMed, EMBASE, Web of Science, and the Cochrane Central Register of Controlled Trials (up to August 10, 2019). A fixed- or random-effects model was employed according to the heterogeneity among studies. The log odds ratios and 95% confidence intervals (CIs) were estimated in the models of allele comparison (T vs C), homozygote comparison (TT vs CC) and (TC vs CC), dominant (TT vs TC + CC), hyperdominant (TT + CC vs TC), and recessive (TT + TC vs CC) to estimate the strength of the associations. A total of 7 case-control studies were included in this meta-analysis. Overall, significant associations between TNF-α T-1031C and EM were identified from (T vs C: log OR [95% CI] = 0.31 [-0.09, 0.71]; TT + CC vs TC: 0.27 [0.04, 0.50]; TC + CC vs TT: -0.83 [-1.19, -0.47]). On the other hand, no significant correlation was found in other gene models (TT vs TC: log OR [95% CI] = 0.89 [0.64, 1.13]; TT vs CC: 0.3 [-0.74, 1.36]; TT + TC vs CC: 0.17 [-0.81, 1.15]). In subgroup analyses by ethnicity or HWE P-value, there was a statistically significant association between TNF-α T-1031C polymorphisms and EM in the dominant model (TT vs TC + CC: log OR [95%] = -0.84 [-1.60, -0.09]) for the European population, and in hyperdominant model (TT + CC vs TC: log OR [95%] = 0.24 [0.001, 0.49]) for Asian population. To sum up, this meta-analysis showed that TNF-α T-1031C polymorphism was associated with EM susceptibility and has a protective effect in Asian and European populations.

Encyclopedia of endometriosis: a pictorial rad-path review

Endometriosis affects approximately 10% of reproductive age women and represents a significant cause of pelvic pain and infertility. Unfortunately, the diagnosis of endometriosis is often delayed by years. Endometriosis may manifest as cystic lesions in the ovaries known as endometriomas. Superficial endometriosis is typically detected by laparoscopy along the pelvic peritoneum as these lesions tend to be difficult to detect by imaging. Deep infiltrative endometriosis may be detected by ultrasound, CT or MRI in classic locations within the pelvis, such as the posterior cul-de-sac and uterosacral ligaments. Endometriosis may also involve the thorax, gastrointestinal and urinary tracts, and locations such as the abdominal wall and abdominal organs. We present MRI and CT case examples, together with corresponding laparoscopic and histopathology images to enhance radiologists' understanding of this disease.

Medical therapy options for endometriosis related pain, which is better? A systematic review and network meta-analysis of randomized controlled trials

Our objective was to assess and rank different pharmacological interventions for relieving endometriosis-related pain. We conducted an online bibliographic search in different databases from their inception until March 2019. We included randomized controlled trials (RCTs) that assessed different medical therapies in the management of endometriosis-related pain. We applied this network meta-analysis (NMA) based on the frequentist approach using statistical package "netmeta" (version 1.0-1) in R software. Our main outcomes were the change in severity of pelvic pain, dysmenorrhea score, non-menstrual pelvic pain score, and dyspareunia score. Overall, 36 RCTs were included in this study (patients no. = 7942). Dienogest (0.94), combined hormonal contraceptives (CHCs) (0.782), and elagolix (0.38) were the highest-ranked interventions for reducing the severity of pelvic pain at three months, while at six months, gonadotropin-releasing hormone (GnRH) analogues (0.75), levonorgestrel-releasing intrauterine system (LNG-IUS) (0.73), and dienogest (0.65) were linked to more reduction in pelvic pain. The ranking p-score showed that GnRH analogues was the highest-ranked treatment for reducing dysmenorrhea at 3 months (1.00), while CHCs were the highest-ranked treatment at 6 months (0.97), followed by GnRH analogues (0.89). GnRH analogues (0.63) and elagolix (0.54) at three months while desogestrel (0.94) and CHCs (0.91) at six months were the highest-ranked treatment to reduce non-menstrual pelvic pain. GnRH analogues and elagolix were the highest-ranked pharmacologic therapies for reducing dyspareunia. In conclusion, CHCs, GnRH analogues, progesterone, and elagolix were the best approaches in reducing the pain of endometriosis.

Activin and inhibin signaling: From regulation of physiology to involvement in the pathology of the female reproductive system

Activins and inhibins - comprising activin A, B, AB, C and E, and inhibin A and B isoforms - belong to the transforming growth factor beta (TGFβ) superfamily. They regulate several biological processes, including cellular proliferation, differentiation and invasiveness, to enhance the formation and functioning of many human tissues and organs. In this review, we have discussed the role of activin and inhibin signaling in the physiological and female-specific pathological events that occur in the female reproductive system. The up-to-date evidence indicates that these cytokines regulate germ cell development, follicular development, ovulation, uterine receptivity, decidualization and placentation through the activation of several signaling pathways; and that their dysregulated expression is involved in the pathogenesis and pathophysiology of the numerous diseases, including pregnancy complications, that disturb reproduction. Hence, some of the isoforms have been suggested as potential biomarkers and therapeutic targets for the management of some of these diseases. Tackling the research directions highlighted in this review will enhance a detailed comprehension and the clinical utility of these cytokines.

Endometriosis in Menopause-Renewed Attention on a Controversial Disease

Endometriosis, an estrogen-dependent inflammatory disease characterized by the ectopic presence of endometrial tissue, has been the topic of renewed research and debate in recent years. The paradigm shift from the belief that endometriosis only affects women of reproductive age has drawn attention to endometriosis in both premenarchal and postmenopausal patients. There is still scarce information in literature regarding postmenopausal endometriosis, the mostly studied and reported being the prevalence in postmenopausal women. Yet, other important issues also need to be addressed concerning diagnosis, pathophysiology, and management. We aimed at summarizing the currently available data in literature in order to provide a concise and precise update regarding information available on postmenopausal endometriosis.

Endometriosis and pain in the adolescent- striking early to limit suffering: A narrative review

Endometriosis, a condition in which uterine tissue grows outside the uterus, is a debilitating disease, affecting millions of women and costing the United States approximately $78 billion annually in pain- related disability. It is also the leading cause of chronic pelvic pain (CPP), which is often unresponsive to existing treatments. Adolescent women with the disease are at particular risk as there are often significant diagnostic delays, which in turn can exacerbate pain. Research and treatment guidelines for adolescents with endometriosis are largely based on studies for adult women due to the limited number of studies focusing on adolescents. The current paper critically reviews the literature as it pertains to endometriosis pathophysiology, mechanisms contributing to CPP, and treatment implications and recommendations with a focus on gaps related to adolescents.

Is Scientific Medical Literature Related to Endometriosis Treatment Evidence-Based? A Systematic Review on Methodological Quality of Randomized Clinical Trials

Background and objectives: Informed decision-making requires the ability to identify and integrate high-quality scientific evidence in daily practice. We aimed to assess whether randomized controlled trials (RCTs) on endometriosis therapy follow methodological criteria corresponding to the RCTs' specific level in the hierarchy of evidence in such details to allow the reproduction and replication of the study. Materials and Methods: Using the keywords "therapy" and "endometriosis" and "efficacy" three bibliographic databases were searched for English written scientific articles published from 1 January 2008 to 3 March 2018. Only the randomized clinical trials (RCTs) were evaluated in terms of whether they provided the appropriate level of scientific evidence, equivalent to level 1, degree 1b in the hierarchy of evidence. A list of criteria to ensure study replication and reproduction, considering CONSORT guideline and MECIR standards, was developed and used to evaluate RCTs' methodological soundness, and scores were granted. Three types of bias, namely selection bias (random sequence generation and allocation concealment), detection bias (blinding of outcome assessment), and attrition bias (incomplete outcome data) were also evaluated. Results: We found 387 articles on endometriosis therapy, of which 38 were RCTs: 30 double-blinded RCTs and 8 open-label RCTs. No article achieved the maximum score according to the evaluated methodological criteria. Even though 73.3% of the double-blinded RCTs had clear title, abstract, introduction, and objectives, only 13.3% provided precise information regarding experimental design and randomization, and also showed a low risk of bias. The blinding method was poorly reported in 43.3% of the double-blinded RCTs, while allocation concealment and random sequence generation were inadequate in 33.3% of them. Conclusions: None of the evaluated RCTs met all the methodological criteria, none had only a low risk of bias and provided sufficient details on methods and randomization to allow for the reproduction and replication of the study. Consequently, the appropriate level of scientific evidence (level 1, degree 1b) could not be granted. On endometriosis therapy, this study evaluated the quality of reporting in RCTs and not the quality of how the studies were performed.

Proposed Key Characteristics of Female Reproductive Toxicants as an Approach for Organizing and Evaluating Mechanistic Data in Hazard Assessment

BACKGROUND

Identification of female reproductive toxicants is currently based largely on integrated epidemiological and in vivo toxicology data and, to a lesser degree, on mechanistic data. A uniform approach to systematically search, organize, integrate, and evaluate mechanistic evidence of female reproductive toxicity from various data types is lacking.

OBJECTIVE

We sought to apply a key characteristics approach similar to that pioneered for carcinogen hazard identification to female reproductive toxicant hazard identification.

METHODS

A working group of international experts was convened to discuss mechanisms associated with chemical-induced female reproductive toxicity and identified 10 key characteristics of chemicals that cause female reproductive toxicity: 1) alters hormone receptor signaling; alters reproductive hormone production, secretion, or metabolism; 2) chemical or metabolite is genotoxic; 3) induces epigenetic alterations; 4) causes mitochondrial dysfunction; 5) induces oxidative stress; 6) alters immune function; 7) alters cell signal transduction; 8) alters direct cell–cell interactions; 9) alters survival, proliferation, cell death, or metabolic pathways; and 10) alters microtubules and associated structures. As proof of principle, cyclophosphamide and diethylstilbestrol (DES), for which both human and animal studies have demonstrated female reproductive toxicity, display at least 5 and 3 key characteristics, respectively. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), for which the epidemiological evidence is mixed, exhibits 5 key characteristics.

DISCUSSION

Future efforts should focus on evaluating the proposed key characteristics against additional known and suspected female reproductive toxicants. Chemicals that exhibit one or more of the key characteristics could be prioritized for additional evaluation and testing. A key characteristics approach has the potential to integrate with pathway-based toxicity testing to improve prediction of female reproductive toxicity in chemicals and potentially prevent some toxicants from entering common use. https://doi.org/10.1289/EHP4971.

Comparative efficacy and safety of traditional Chinese patent medicine for endometriosis: A Bayesian network meta-analysis protocol

BACKGROUND

Endometriosis is a common disease of women of childbearing age. In recent years, the incidence of endometriosis has been on the rise. The main clinical manifestations are pelvic pain and infertility. In recent years, traditional Chinese patent medicine (TCMP) has played an important role in the treatment of endometriosis. So far, there is a lack of comparison among all the current common TCPMs for endometriosis. Consequently, it is indispensable to propose a network meta-analysis (NMA) protocol to discuss the strengths and weaknesses of different TCMPs.

METHODS

We will comprehensively and systematically retrieve the relevant Chinese and English databases from their inceptions to the May 2019. All randomized controlled trials (RCTs) of TCMPs for Endometriosis will be included. Two researchers will independently screen literature, extract data and assess the risk of bias of included studies. We will conduct pairwise meta-analyses and Bayesian network meta-analyses to assess all the available evidence. Data will be analyzed using STATA and WinBUGS software.

RESULTS

This work will compare and rank the relative efficacy of different TCPMs in the treatment of endometriosis in detail.

CONCLUSION

The results of this study will provide reliable evidence for the selection of clinical treatment program and guideline development.

PROSPERO REGISTRATION NUMBER

CRD42019127781.