PLOS ONE RESEARCH ARTICLE Methodological transparency of preoperative clinical practice guidelines for elective surgery. Systematic review Gustavo Angel1, Cristian Trujillo1, Mario Mallama1, Pablo Alonso-Coello2, Markus Klimek ID3, Jose A. Calvache ID1,3* 1 Department of Anesthesiology, Universidad del Cauca, Cauca, Colombia, 2 Iberoamerican Cochrane Centre, Clinical Epidemiology and Public Health Department, Hospital de la Santa Creu i Sant Pau, Universitat Autonoma de Barcelona, Barcelona, Spain, 3 Department of Anesthesiology, Erasmus University Medical Centre Rotterdam, Rotterdam, The Netherlands a1111111111 a1111111111 * jacalvache@unicauca.edu.co a1111111111 a1111111111 a1111111111 Abstract Background OPEN ACCESS Clinical practice guidelines (CPG) are statements that provide recommendations regarding Citation: Angel G, Trujillo C, Mallama M, Alonso- Coello P, Klimek M, Calvache JA (2023) the approach to different diseases and aim to increase quality while decreasing the risk of Methodological transparency of preoperative complications in health care. Numerous guidelines in the field of perioperative care have clinical practice guidelines for elective surgery. been published in the previous decade but their methodological quality and transparency Systematic review. PLoS ONE 18(2): e0272756. are relatively unknown. https://doi.org/10.1371/journal.pone.0272756 Editor: Seung-Hwa Lee, Samsung Medical Center, REPUBLIC OF KOREA Objective Received: August 3, 2022 To critically evaluate the transparency and methodological quality of published CPG in the Accepted: February 5, 2023 preoperative assessment and management of adult patients undergoing elective surgery. Published: February 24, 2023 Peer Review History: PLOS recognizes the Design benefits of transparency in the peer review Systematic review and methodological appraisal study. process; therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. The editorial history of this article is available here: Data sources https://doi.org/10.1371/journal.pone.0272756 We searched for eligible CPG published in English or Spanish between January 1, 2010, Copyright: © 2023 Angel et al. This is an open and June 30, 2022, in Pubmed MEDLINE, TRIP Database, Embase, the Cochrane Library, access article distributed under the terms of the as well as in representatives’ medical societies of Anaesthesiology and developers of CPG. Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original Eligibility criteria author and source are credited. CPG dedicated on preoperative fasting, cardiac assessment for non-cardiac surgery, and Data Availability Statement: All relevant data are within the paper and its Supporting Information the use of routine preoperative tests were included. Methodological quality and transpar- files. ency of CPG were assessed by 3 evaluators using the 6 domains of the AGREE-II tool. PLOS ONE | https://doi.org/10.1371/journal.pone.0272756 February 24, 2023 1 / 14 PLOS ONE Preoperative clinical practice guidelines. Systematic review Funding: This work was supported by Results departmental funding (Department of Anesthesiology, Universidad del Cauca, Colombia, We included 20 CPG of which 14 were classified as recommended guidelines. The domain and Department of Anesthesiology, Erasmus of "applicability" scored the lowest (44%), while the domains "scope and objective" and "edi- University Medical Centre Rotterdam, The torial interdependence" received the highest median scores of 93% and 97% respectively. Netherlands). The funders had no role in study design, data collection and analysis, decision to The remaining domains received scores ranging from 44% to 84%. The top mean scored publish, or preparation of the manuscript. CPG in preoperative fasting was ASA 2017 (93%); among cardiac evaluation, CPG for non- Competing interests: The authors have declared cardiac surgery were CCS 2017 (91%), ESC-ESA 2014 (90%), and AHA-ACC 2014 (89%); that no competing interests exist. in preoperative testing ICSI 2020 (97%). Conclusions In the last ten years, most published CPG in the preoperative assessment or management of adult patients undergoing elective surgery focused on preoperative fasting, cardiac assessment for non-cardiac surgery, and use of routine preoperative tests, present moder- ate to high methodological quality and can be recommended for their use or adaptation. Applicability and stakeholder involvement domains must be improved in the development of future guidelines. Introduction Much of the global burden of disease requires surgical intervention and over 234 million oper- ations are conducted each year worldwide [1, 2]. Lack of timely access to high-quality surgical care remains a major problem in much of the world, even though surgical interventions can be cost-effective interventions in terms of lives saved and disabilities avoided [3]. In addition, perioperative period is frequently associated with morbidity and mortality [4]; in high-income countries, major complications are occurring in 3 to 16% of in-hospital surgeries leading to permanent disability or mortality ranging from 0.4 to 0.8%, while increased to 5% to 10% in low- and middle-income countries [5]. Clinical practice guidelines (CPG) are statements containing evidence-based recommenda- tions aimed at providing better patient care and helping physicians and patients to make the best decisions for the prevention, diagnosis, and treatment of different diseases [6]. The use of CPG during preoperative assessment and treatment of patients before surgical procedures can contribute to reducing the risk of complications, increase patient safety, improve the quality of care, enable the implementation of effective interventions, decrease treatment variability, and finally improve patient outcomes [7]. The development of high-quality CPG is a complex, lengthy, and systematic scientific pro- cess involving developers, stakeholders, and users, and therefore, the development process and produced recommendations can present varying degrees of quality [6, 8]. CPG have been eval- uated by several authors including numerous conditions and years of development and publi- cation (from 1980 to 2019). In general, the applicability domain has received the lowest mean score, and improvement in time is still a matter of controversy [9–12]. On perioperative care, Barajas-Nava et al., evaluated 22 CPG from 1990 up to 2008 describ- ing their quality as moderate for most of the domains with the lowest scores in stakeholder involvement, applicability and editorial independence [7]. Ciapponi et al. reported the domain “applicability” as the worst score in preoperative (2010 to 2017) CPG [13]. In addition, a recent evaluation of guidelines in airway management, as part of perioperative care, showed applica- bility scores of around 23% [14]. Studies were not able to detect any improvement over time in PLOS ONE | https://doi.org/10.1371/journal.pone.0272756 February 24, 2023 2 / 14 PLOS ONE Preoperative clinical practice guidelines. Systematic review CPG quality, specifically in this context [7, 14], and show opportunities to improve the quality of CPG development [13]. We aimed to critically evaluate the transparency and methodological quality of the develop- ment of published CPG in the preoperative assessment and management of adult patients undergoing elective surgery published in the last decade, by using the AGREE-II tool. Methods Design Systematic review including published CPG in preoperative care with a descriptive, methodo- logical, and quality appraisal approach [15]. The reporting of this systematic review was guided by the standards of the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) Statement, table in S1 Appendix. Search strategy We conducted an extensive search in PubMed MEDLINE, TRIP Database, Embase, and the Cochrane Library, as well as on 12 specific dedicated websites for CPG developers, text in S2 Appendix. In addition, we explored all relevant medical societies (World Federation of Societies of Anaesthesiologists (WFSA), American Society of Anesthesiologists (ASA), Euro- pean Society of Anaesthesiology (ESA), Association of Anaesthetists of Great Britain and Ire- land (AAGBI), and Canadian Anesthesiologists’ Society (CAS)). Our search was limited to CPG published between January 1, 2010, and June 30, 2022, that were written or published in English or Spanish. All searches were performed in December 2021 and updated in June 2022. The protocol of this study was previously published (PROSPERO ID 200026) [16]. Selection process We defined a CPG as any document comprising clinical recommendations for the preopera- tive assessment or treatment of adult patients undergoing elective surgery classifying them into three categories related to 1) Preoperative fasting, 2) Cardiac assessment for non-cardiac surgery, and 3) Use of routine preoperative tests (laboratory test, X-ray, pulmonary function test, and electrocardiogram). CPG designed for the assessment and management of specific conditions or designed for specific individuals were excluded (i.e., obstructive sleep apnoea, diabetes mellitus, specific surgeries, or designed only for obstetric patients, paediatric patients, or other specific populations). Data collection process and quality appraisal Two reviewers (C.T. and G.A) screened independently the records based on the eligibility criteria and three independent reviewers (C.T., G.A., and M.M.) conducted data extraction and assess- ment by using a validated form in the online tool My Agree Plus (https://www.agreetrust.org/). All evaluators underwent a thorough detailed training for the AGREE-II tool application by fol- lowing two major online-training modules to assist users in effectively applying the tool. The first one contains an avatar-guided overview of the AGREE II tool and follows a step-by-step process to complete each item and domain. It also provides immediate feedback on how the trainees’ responses compare with those of expert ratings. The second one is an online-based tutorial with a virtual coach accompanied by a practice appraisal exercise. This strategy has been previously tested [17]. Any discrepancy was solved by consensus with the advice of a fourth reviewer (J.A.C.). The following data were obtained: the main category of the CPG, the number of authors, year of PLOS ONE | https://doi.org/10.1371/journal.pone.0272756 February 24, 2023 3 / 14 PLOS ONE Preoperative clinical practice guidelines. Systematic review publication or update, type of institution (governmental institution, specialty society or con- sortium, and university), version of the guideline (first and revision/updated), region of origin, reported funding (yes/no), the method for guideline development (systematic review, consen- sus or narrative review, adaptation or adoption, and not mentioned), methods to formulate recommendations (formal, informal consensus, and not mentioned), and methods to grade evidence (yes/no). We used the revised version of the Appraisal of Guidelines for Research and Evaluation (AGREE-II) to assess the quality of CPG. The AGREE is a validated and widely used tool to assess CPG quality, and its components are based on the elements for high-quality CPG defined by the National Academy of Medicine (formerly Institute of Medicine) and by the Guidelines International Network [8]. AGREE-II comprises 23 items organized in six domains and two global rating items (overall assessments). Each domain assesses a different dimension of the CPG quality: scope and purpose (domain 1), stakeholder involvement (domain 2), rigor of development (domain 3), clarity of presentation (domain 4), applicability (domain 5), and editorial independence (domain 6) (8). Each item was rated using a seven-point Likert scale ranging from 1 (strongly disagree) to 7 (strongly agree). Data analysis The score for each AGREE-II domain was calculated as the sum of all scores of the individual items in the domain and the total was standardized as a percentage of the maximum possible score for that domain, using the following formula: (score obtained–minimum possible score)/(maximum score–minimum possible score) x 100. With the results from each evaluator, a summary table was designed to generate median values for each domain and interquartile range (IQR). Another researcher (J.A.C.) analysed results to obtain the degree of concordance of the evaluation; in which ‘score obtained’ was the sum of the scores by individual evaluators, maximum score = 7 (strongly agree) x 3 (evaluators) x number of items in the domain and min- imum score = 1 (strongly disagree) x 3 (evaluators) x number of items in the domain [14, 18]. The overall mean quality score classified the CPG as ‘recommended’ (>60%), ‘recom- mended with modifications’ (30 to 60%), or ‘not recommended’ (<30%) to be applied in clini- cal practice. Finally, an absolute agreement among the three reviewers was determined by using the intraclass correlation coefficient with its 95% confidence interval, based on a mean- rating (k = 3), two-way random-effects model. A standardized score was calculated separately for each of the six domains, and it was classified as a poor agreement (<0.50), moderate (0.50 to 0.75), good (0.75 to 0.90), and excellent (>0.90). The data were analysed with the IBM SPSS 25.0 package for Windows (Armonk, NY: IBM Corp.), and R Statistics. Results We included 20 CPG in our analysis (Fig 1). During our eligibility process, we excluded 14 CPG, text in S3 Appendix. Based on the mean quality score, 14 CPG (70%) were classified as “recommended” to be implemented in clinical practice (Tables 1 and 2). A total of 16 CPG (80%) were produced by medical societies, 12 (60%) were new guidelines (first version), and only 10 (50%) explicitly reported the source of funding for development. Most CPG (95%) described they used a systematic review process and only six (30%) reported a formal method for achieving consensus. Considering all CPG, the highest AGREE-II median scores were observed in the domains “scope and objective” (93%), “clarity of presentation” (84%), and “editorial independence” (97%). The lowest median scores were assigned to “stakeholder involvement” and “applicabil- ity” (56% and 44%, respectively) (Fig 2, Table 2). Overall, CPG focused on the use of routine PLOS ONE | https://doi.org/10.1371/journal.pone.0272756 February 24, 2023 4 / 14 PLOS ONE Preoperative clinical practice guidelines. Systematic review Fig 1. Search and selection process of CPG. https://doi.org/10.1371/journal.pone.0272756.g001 preoperative tests were rated higher than CPG related to cardiac assessment for non-cardiac surgery and CPG related to preoperative fasting (81% versus 73% and 74% respectively). The highest mean rated CPG among the preoperative fasting category was the ASA 2017 (93%) [19]; among the cardiac evaluation for non-cardiac surgery CPG were CCS 2017 (91%) [20], ESC-ESA 2014 (90%) [21], and AHA-ACC 2014 (89%) [22]. Finally, ICSI 2020 [23] was the best-rated CPG in the preoperative testing category (97%) (Table 2). Inter-rater agreement was rated as good to excellent for all domains (Table 3). PLOS ONE | https://doi.org/10.1371/journal.pone.0272756 February 24, 2023 5 / 14 PLOS ONE Preoperative clinical practice guidelines. Systematic review Table 1. Characteristics of included CPG stratified by recommendation status� (n = 20). Characteristic No. (% of the Recommended CPG n = 14 No. (% per Recommended with modifications CPG n = 6 No. (% per total) category) category) Main topic Preoperative fasting 6 (30) 4 (67) 2 (33) Cardiac assessment for non-cardiac 11 (55) 8 (73) 3 (27) surgery Use of routine preoperative tests 3 (15) 2 (67) 1 (33) Year of publication 2010 1 (5) 1 (100) 0 (0) 2011 5 (25) 3 (60) 2 (40) 2014 3 (15) 2 (67) 1 (33) 2016 3 (15) 1 (33) 2 (67) 2017 4 (20) 4 (100) 0 (0) 2018 1 (5) 1 (100) 0 (0) 2019 1 (5) 0 (0) 1 (100) 2020 1 (5) 1 (100) 0 (0) 2021 1 (5) 1 (100) 0 (0) Number of authors �5 1 (5) 0 (0) 1 (100) 6–10 5 (25) 4 (80) 1 (20) 11–20 6 (30) 4 (67) 2 (33) � 20 8 (40) 6 (75) 2 (25) Type of institution Governmental institution 2 (10) 2 (100) 0 (0) Specialty society or consortium 16 (80) 10 (63) 6 (37) University or academic institution 2 (10) 2 (100) 0 (0) Region United States 4 (20) 4 (100) 0 (0) United Kingdom 2 (10) 2 (100) 0 (0) Belgium 2 (10) 2 (100) 0 (0) Argentine 2 (10) 0 (0) 2 (100) Brazil 2 (10) 1 (50) 1 (50) Canada 1 (5) 1 (100) 0 (0) Germany 1 (5) 1 (100) 0 (0) Denmark 1 (5) 1 (100) 0 (0) Spain 1 (5) 0 (0) 1 (100) Japan 1 (5) 0 (0) 1 (100) Mexico 1 (5) 1 (100) 0 (0) Singapore 1 (5) 0 (0) 1 (100) South Africa 1 (5) 1 (100) 0 (0) Guideline version First version 12 (60) 9 (75) 3 (25) Revision or updated version 8 (40) 5 (63) 3 (37) Method for guideline development Systematic review 19 (95) 14 (73) 5 (27) Not mentioned 1 (5) 0 (0) 1 (100) Recommendation methods Not mentioned 4 (20) 0 (0) 4 (100) Informal consensus 10 (50) 9 (90) 1 (10) Formal consensus 6 (30) 5 (83) 1 (17) Funding Clearly reported 10 (50) 10 (100) 0 (0) Not mentioned 10 (50) 0 (0) 6 (100) � The overall quality AGREE-II score classified the CPG as ‘recommended’ (>60%), ‘recommended with modifications’ (30 to 60%), or ‘not recommended’ (<30%) https://doi.org/10.1371/journal.pone.0272756.t001 PLOS ONE | https://doi.org/10.1371/journal.pone.0272756 February 24, 2023 6 / 14 PLOS ONE Preoperative clinical practice guidelines. Systematic review Table 2. Scores of the AGREE-II domains for 20 included CPG stratified by category and recommendation status� . Category CPG AGREE-II domains Scope and Stakeholder Rigour of Clarity of Applicability Editorial Mean objective involvement development presentation (%) independence score (%) (%) (%) (%) (%) (%) Preoperative fasting ASA 2017 [19] 98 89 85 94 90 100 93 ESN 2017 [24] 98 52 83 83 68 100 81 ESA 2011 [25] 91 61 67 83 32 100 72 ASA 2011 [26] 96 65 78 78 56 0 62 AAA 2016 [27] 70 20 34 59 6 89 46 CAS 2019 [28] 72 28 25 54 10 33 37 Cardiac assessment for non- CCS 2017 [20] 91 93 90 96 75 100 91 cardiac surgery ESC-ESA 2014 98 83 76 98 86 100 90 [21] AHA-ACC 2014 93 85 89 91 78 100 89 [22] ESA 2018 [4] 98 69 90 89 72 83 84 ESA 2011 [29] 98 70 77 83 36 100 78 GFM 2010 [30] 100 56 67 74 40 97 72 BSC 2017 [31] 85 39 34 91 43 94 64 SA 2021 [32] 72 50 56 78 39 83 63 SAC 2016 [33] 81 30 64 87 38 0 50 BSC 2011 [34] 65 28 25 85 38 53 49 JCS 2011 [35] 57 54 41 65 44 0 44 Use of routine preoperative ICSI 2020 [23] 94 98 95 98 97 100 97 tests NICE 2016 [36] 98 56 61 93 81 100 81 SEA 2014 [37] 93 52 31 65 3 97 57 Overall results Median score 93 56 67 84 44 97 IQR 79 to 98 47 to 74 39 to 84 77 to 91 37 to 76 75 to 100 � Recommended CPG classification (Grey shading, n = 14); Recommended with modifications (White shading, n = 6). https://doi.org/10.1371/journal.pone.0272756.t002 Mean AGREE-II scores among the included CPG ranged from 37% to 97% without major changes in the mean CPG scores over time (Table 2). Among the recommended CPG (n = 14, 62% to 97%), 10 reported funding, 2 were produced by governmental institutions, 10 by medi- cal societies, and 2 by universities or academic institutions. In contrast, none of the CPG rec- ommended with modifications reported funding, none were developed by governmental or academic institutions, and all were produced by medical societies. Overall, the most frequent characteristics presented in the recommended CPGs were being produced by governmental institutions (2 of 2, 100%), involving more than 20 authors (6 of 8, 75%), being the first version (9 of 12, 75%), reporting funding (10 of 10, 100%), and being developed by following a system- atic review process (14 of 19, 73%) (Table 1). The number of included guidelines in this study prevents a more detailed analysis of associated factors. Discussion This systematic review included 20 CPG related to preoperative assessment and management of adult patients undergoing elective surgery. In the cardiac evaluation for non-cardiac surgery guidelines, two CPG (CCS 2017 [20] and ESC-ESA 2014 [21]) obtained AGREE-II scores equal or above 90%; In preoperative fasting, one CPG (ASA 2017 [19]) obtained a score of PLOS ONE | https://doi.org/10.1371/journal.pone.0272756 February 24, 2023 7 / 14 PLOS ONE Preoperative clinical practice guidelines. Systematic review Fig 2. Median scores of CPG evaluated in six domains of the AGREE-II instrument stratified by category (n = 20). https://doi.org/10.1371/journal.pone.0272756.g002 Table 3. Inter-rater agreement of AGREE II domains. Domain Inter-rater agreement� Intra-class correlation coefficient (ICC) 95% CI Degree of agreement Scope and objective 0.92 0.84 to 0.96 Excellent Stakeholder involvement 0.96 0.92 to 0.98 Excellent Rigour of development 0.96 0.92 to 0.98 Excellent Clarity of presentation 0.86 0.59 to 0.94 Good Applicability 0.95 0.90 to 0.98 Excellent Editorial independence 0.96 0.90 to 0.98 Excellent � Intra-class correlation coefficient. Poor agreement (<0.50), moderate (0.50 to 0.75), good (0.75 to 0.90), and excellent (>0.90). https://doi.org/10.1371/journal.pone.0272756.t003 PLOS ONE | https://doi.org/10.1371/journal.pone.0272756 February 24, 2023 8 / 14 PLOS ONE Preoperative clinical practice guidelines. Systematic review 93%, and in preoperative testing, one CPG (ICSI 2020 [23]) obtained a score of 97%. In gen- eral, 14 of 20 included CPG were classified as recommended to be used in clinical practice. The domain “applicability” had the lowest scores; this has also been found extensively in other related studies [9–12, 38]. On perioperative care and airway management, applicability has been rated low [7, 13, 14]. Considering CPG are designed to be widely used, these findings represent important challenges to the guideline’s development and implementation. Many of the current CPG do not consider the inclusion of tools and strategies that facilitate their appli- cation in real clinical scenarios or barriers that limit their use. Sometimes, CPG do not provide insights on how the recommendations can be put into practice or regarding the resource con- sequences of applying them (i.e., in limited resources settings). That can be translated into a low score in this domain. In addition, the opinion of patients or patients’ representatives is rarely described in the development of recommendations resulting in low scores found in the domain “stakeholder involvement”. Recent developments of CPG may be reflected by a continuous increase in some domains [39]. The domain "scope and objective" received a high score, showing that most included guidelines have a clear objective, a well-defined population under consideration, and some specific focused clinical questions. In the perioperative scenario, this remains a high-rated domain without major differences from previous assessments [7, 13]. Editorial independence is critical in the process of developing high-quality CPG [40] and it has been previously reported as one of the lowest scored domains [7]. Results of this study show that in the preoperative assessment and treatment of adult patients before elective sur- gery, most available guidelines of the last decade can be considered independent, in line with a recent assessment [13]. Across domains, editorial independence obtained the highest score (97%) but there are some CPG scoring zero in this domain. While this finding adds confidence to the provided recommendations by reducing the risk of delivering biased recommendations or being influenced by sponsors (seeking their benefits) or by the pharmaceutical industry, there are still some CPG produced without a clear and transparent editorial independence. This large scor- ing variability also reflects the relative importance each sponsor gives to the editorial indepen- dence process during development, and the great implications to reviewers and evaluators during judging this domain. Most of the included CPG were produced by specialty societies but specific conflicts of interest were declared as well as their potential effect on the development process and content of the guideline with transparency. All CPG classified as recommended reported their funding sources while none of the recommended with modifications did. Methodological procedures used to generate recommendations are critical steps outlined by AGREE-II as the “rigour of development” domain. In comparisons to previous studies [9] and other related perioperative scenarios [14], included guidelines presented a median score of 67%, with higher scores for CPG produced in Europe, United States, and Canada. From 1980 to 2007, a very slow increase in quality in CPG was reported [9] However, in the last decade, the AGREE-II tool has become the most widely used international “gold standard” for guidelines development [41], potentially supporting the improvement in this area. Recently Ciapponi et al., published a systematic review focused to summarize and compare recommendations presented in evidence-based CPG for preoperative care [13]. Including 16 CPG, they reported many strong recommendations ready to be considered for implementa- tion. In line with these findings, our results classified most included CPG as “recommended”. In addition, when comparing our findings, they do not differ to a greater extent, being consis- tent that the domains top-scored were “scope and objective”, "Clarity of presentation", and "editorial independence". Also, “applicability” was the lowest rated. Low applicability can be explained by the difference in the populations to which the inter- vention is directed or by the lack of technological resources to perform such intervention in PLOS ONE | https://doi.org/10.1371/journal.pone.0272756 February 24, 2023 9 / 14 PLOS ONE Preoperative clinical practice guidelines. Systematic review different settings. In addition, as stated by Ciapponi et al., an inadequate adoption of guide- lines (due to the tendency of many physicians to practice a "defensive medicine"), results in unnecessary interventions only to avoid legal problems and concerns derived from the care [13]. This is especially important for the use of routine preoperative tests. There are three major barriers to CPG implementation described in the literature. Personal factors (related to physicians’ knowledge and attitudes), guideline-related factors, and external factors [42]. In addition, central elements of successful strategies for CPG implementation include dissemination, education and training, social interaction, decision support systems, and standing orders. A whole adjusted and adapted process is needed in advance when surgical teams are trying to implement a new guideline. Recent evidence indicates that only by follow- ing a structured process that includes an analysis of the potential local-related barriers, imple- mentation and adherence can be effective [42]. This study did have some limitations. First, AGREE-II items do not include a category “does not apply”. In some cases, information to evaluate a single domain is missing and doubt remains as to how this should be scored and rated. Second, the degree of training required to allow an adequate and valid evaluation of a CPG is always a matter of concern, and certain subjective judgments may be present between evaluators. In our case, a detailed training pro- cess was implemented for the three evaluators regarding the application of the AGREE II tool, resulting in an agreement rated from good to excellent for all included areas. Third, to include updated versions of certain CPG may be controversial but it also allows us to compare the change in score with the previous versions. Finally, while most CPG are published in English, we included only CPG published in English and Spanish losing some relevant information from particular countries. Healthcare providers use CPG considering guidelines to provide recommendations based on the best available evidence [43]. However, a 2009 study reported that most of the evidence used in the American College of Cardiology / American Heart Association CPG was based on expert recommendations [44], commonly non scientifically validated opinions. A systematic review of the evidence-based CPG published by the American and European scientific socie- ties in anaesthesiology has recently been published. Their authors evaluated the quality of the evidence used to provide recommendations, finding that only 16% of them were based on level A of evidence, 33% on level B of evidence, and 51% on level C of evidence. These findings imply a critical need for greater efforts to improve the evidence used in the future CPG [43]. In our study, the limited number of CPG prevents a more detailed analysis of the factors associ- ated with high methodological quality; further studies to assess the relationship between char- acteristics of CPG developers and the quality of CPG are warranted as they are available in other scenarios [45]. In 2022, O’Shaughnessy et al., assessed the quality of CPG published during the last 5 years in top anesthesia journals. With a scope beyond the preoperative care, they included 51 CPG with low scores to “stakeholder involvement”, “rigor of development” and “applicability” domains [46] Additionally, Mai et al. in 2021, evaluated 96 CPG in anesthesiology practice finding “rigor of development” and “applicability” as the lowest rated domains [47]. Publica- tion of a CPG in a peer-reviewed high-quality journal may enhances the scientific credentials of the process [48] while reducing the potential inclusion CPG produced by low- and middle- income countries or in any language different from English. In addition, time barriers, peer review and the overall editorial process may distort and delay the original message and recom- mendations as part of the development of the guideline [49, 50]. In conclusion, CPG in the preoperative assessment or management of adult patients under- going elective surgery including preoperative fasting, cardiac assessment for non-cardiac sur- gery, and use of routine preoperative tests present moderate to high methodological quality PLOS ONE | https://doi.org/10.1371/journal.pone.0272756 February 24, 2023 10 / 14 PLOS ONE Preoperative clinical practice guidelines. Systematic review and can be recommended for their use or adaptation. Domains of applicability and stake- holder involvement must be improved in the development of future guidelines. Supporting information S1 File. (DOCX) S1 Appendix. PRISMA 2020- checklist of items that should be included in systematic review. (DOCX) S2 Appendix. Search strategies. (DOCX) S3 Appendix. Excluded CPG during eligibility process. (DOCX) Acknowledgments Assistance with the study: The authors are grateful to the Medical Library, Erasmus Univer- sity Medical Centre Rotterdam for assistance with the literature search. Presentation: Preliminary data for this study were presented as a poster presentation at the Colombian Society of Anesthesiology meeting, 5–7 August 2021. Author Contributions Conceptualization: Gustavo Angel, Cristian Trujillo, Mario Mallama, Pablo Alonso-Coello, Markus Klimek, Jose A. Calvache. Data curation: Gustavo Angel, Cristian Trujillo, Mario Mallama, Markus Klimek, Jose A. Calvache. Formal analysis: Jose A. Calvache. Funding acquisition: Gustavo Angel. 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