Update of the agency for healthcare research and quality guidance on using nonrandomized studies in evidence syntheses.

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Development and design validation of a novel network meta-analysis presentation tool for multiple outcomes: a qualitative descriptive study.

OBJECTIVE: The Grades of Recommendations, Assessment, Development and Evaluation working group recently developed an innovative approach to interpreting results from network meta-analyses (NMA) through minimally and partially contextualised methods; however, the optimal method for presenting results for multiple outcomes using this approach remains uncertain. We; therefore, developed and iteratively modified a presentation method that effectively summarises NMA results of multiple outcomes for clinicians using this new interpretation approach. DESIGN: Qualitative descriptive study. SETTING: A steering group of seven individuals with experience in NMA and design validation studies developed two colour-coded presentation formats for evaluation. Through an iterative process, we assessed the validity of both formats to maximise their clarity and ease of interpretation. PARTICIPANTS: 26 participants including 20 clinicians who routinely provide patient care, 3 research staff/research methodologists and 3 residents. MAIN OUTCOME MEASURES: Two team members used qualitative content analysis to independently analyse transcripts of all interviews. The steering group reviewed the analyses and responded with serial modifications of the presentation format. RESULTS: To ensure that readers could easily discern the benefits and safety of each included treatment across all assessed outcomes, participants primarily focused on simple information presentations, with intuitive organisational decisions and colour coding. Feedback ultimately resulted in two presentation versions, each preferred by a substantial group of participants, and development of a legend to facilitate interpretation. CONCLUSION: Iterative design validation facilitated the development of two novel formats for presenting minimally or partially contextualised NMA results for multiple outcomes. These presentation approaches appeal to audiences that include clinicians with limited familiarity with NMAs.

Pooling of cohort studies and RCTs affects GRADE certainty of evidence in nutrition research.

BACKGROUND: There is a little empirical evidence of the impact of pooling randomized controlled trials (RCTs) and cohort studies (CSs) on the certainty-of-evidence. To evaluate the hypothetical-scenario of pooling bodies-of-evidence from RCTs with matched bodies-of-evidence from CSs on the certainty-of-evidence. METHODS: We extracted GRADE ratings of bodies-of-evidence from RCTs in Cochrane reviews, and rated the certainty-of-evidence from matched bodies-of-evidence from CSs. We then evaluated the impact of pooling both bodies-of-evidence on the overall certainty-of-evidence, and on individual GRADE domains. RESULTS: Fourty-two pooled bodies-of-evidence were rated, ranging from very-low (bodies-of-evidenceRCTs: 9.5%; bodies-of-evidenceCSs: 40.5%; pooled-bodies-of-evidence: 0%) to low (bodies-of-evidenceRCTs: 38.1%; bodies-of-evidenceCSs: 45.2%; pooled-bodies-of-evidence: 19.1%), moderate (bodies-of-evidenceRCTs: 33.4%; bodies-of-evidenceCSs: 14.3%; pooled-bodies-of-evidence: 57.1%), and high (bodies-of-evidenceRCTs: 19%; bodies-of-evidenceCSs: 0%; pooled-bodies-of-evidence: 23.8%). Certainty-of-evidence was downgraded mostly for imprecision and risk of bias for bodies-of-evidence from RCTs, and for risk of bias and inconsistency for bodies-of-evidence from CSs. Pooling both bodies-of-evidence mitigates rating down for imprecision compared to bodies-of-evidence from RCTs and inconsistency compared to bodies-of-evidence from CSs. CONCLUSION: Our hypothetical study suggests that pooling both bodies-of-evidence would reduce the amount of very-low and low certainty-of-evidence ratings, but how to integrate RCTs and CSs and whether or not to pool these bodies-of-evidence requires proper guidance before systematic review authors or guideline developers should consider this approach.

GRADE guidance 24 optimizing the integration of randomized and non-randomized studies of interventions in evidence syntheses and health guidelines.

BACKGROUND AND OBJECTIVE: This is the 24th in the ongoing series of articles describing the GRADE approach for assessing the certainty of a body of evidence in systematic reviews and health technology assessments and how to move from evidence to recommendations in guidelines. METHODS: Guideline developers and authors of systematic reviews and other evidence syntheses use randomized controlled studies (RCTs) and non-randomized studies of interventions (NRSI) as sources of evidence for questions about health interventions. RCTs with low risk of bias are the most trustworthy source of evidence for estimating relative effects of interventions because of protection against confounding and other biases. However, in several instances, NRSI can still provide valuable information as complementary, sequential, or replacement evidence for RCTs. RESULTS: In this article we offer guidance on the decision regarding when to search for and include either or both types of studies in systematic reviews to inform health recommendations. CONCLUSION: This work aims to help methodologists in review teams, technology assessors, guideline panelists, and anyone conducting evidence syntheses using GRADE.

COVID-19 transmission during swimming-related activities: a rapid systematic review.

BACKGROUND: There are uncertainties about mitigating strategies for swimming-related activities in the context of the COVID-19 pandemic. There is an opportunity to learn from the experience of previous re-openings to better plan the future one. Our objectives are to systematically review the evidence on (1) the association between engaging in swimming-related activities and COVID-19 transmission; and (2) the effects of strategies for preventing COVID-19 transmission during swimming-related activities. METHODS: We conducted a rapid systematic review. We searched in the L·OVE (Living OVerview of Evidence) platform for COVID-19. The searches covered the period from the inception date of each database until April 19, 2021. We included non-randomized studies for the review on association of COVID-19 transmission and swimming-related activities. We included guidance documents reporting on the strategies for prevention of COVID-19 transmission during swimming-related activities. We also included studies on the efficacy and safety of the strategies. Teams of two reviewers independently assessed article eligibility. For the guidance documents, a single reviewer assessed the eligibility and a second reviewer verified the judgement. Teams of two reviewers extracted data independently. We summarized the findings of included studies narratively. We synthesized information from guidance documents according to the identified topics and subtopics, and presented them in tabular and narrative formats. RESULTS: We identified three studies providing very low certainty evidence for the association between engaging in swimming-related activities and COVID-19 transmission. The analysis of 50 eligible guidance documents identified 11 topics: ensuring social distancing, ensuring personal hygiene, using personal protective equipment, eating and drinking, maintaining the pool, managing frequently touched surfaces, ventilation of indoor spaces, screening and management of sickness, delivering first aid, raising awareness, and vaccination. One study assessing the efficacy of strategies to prevent COVID-19 transmission did not find an association between compliance with precautionary restrictions and COVID-19 transmission. CONCLUSIONS: There are major gaps in the research evidence of relevance to swimming-related activities in the context of the COVID-19 pandemic. However, the synthesis of the identified strategies from guidance documents can inform public health management strategies for swimming-related activities, particularly in future re-opening plans.

Ventilation Techniques and Risk for Transmission of Coronavirus Disease, Including COVID-19: A Living Systematic Review of Multiple Streams of Evidence.

BACKGROUND: Mechanical ventilation is used to treat respiratory failure in coronavirus disease 2019 (COVID-19). PURPOSE: To review multiple streams of evidence regarding the benefits and harms of ventilation techniques for coronavirus infections, including that causing COVID-19. DATA SOURCES: 21 standard, World Health Organization-specific and COVID-19-specific databases, without language restrictions, until 1 May 2020. STUDY SELECTION: Studies of any design and language comparing different oxygenation approaches in patients with coronavirus infections, including severe acute respiratory syndrome (SARS) or Middle East respiratory syndrome (MERS), or with hypoxemic respiratory failure. Animal, mechanistic, laboratory, and preclinical evidence was gathered regarding aerosol dispersion of coronavirus. Studies evaluating risk for virus transmission to health care workers from aerosol-generating procedures (AGPs) were included. DATA EXTRACTION: Independent and duplicate screening, data abstraction, and risk-of-bias assessment (GRADE for certainty of evidence and AMSTAR 2 for included systematic reviews). DATA SYNTHESIS: 123 studies were eligible (45 on COVID-19, 70 on SARS, 8 on MERS), but only 5 studies (1 on COVID-19, 3 on SARS, 1 on MERS) adjusted for important confounders. A study in hospitalized patients with COVID-19 reported slightly higher mortality with noninvasive ventilation (NIV) than with invasive mechanical ventilation (IMV), but 2 opposing studies, 1 in patients with MERS and 1 in patients with SARS, suggest a reduction in mortality with NIV (very-low-certainty evidence). Two studies in patients with SARS report a reduction in mortality with NIV compared with no mechanical ventilation (low-certainty evidence). Two systematic reviews suggest a large reduction in mortality with NIV compared with conventional oxygen therapy. Other included studies suggest increased odds of transmission from AGPs. LIMITATION: Direct studies in COVID-19 are limited and poorly reported. CONCLUSION: Indirect and low-certainty evidence suggests that use of NIV, similar to IMV, probably reduces mortality but may increase the risk for transmission of COVID-19 to health care workers. PRIMARY FUNDING SOURCE: World Health Organization. (PROSPERO: CRD42020178187).

Grading of Recommendations Assessment, Development, and Evaluations (GRADE) notes: extremely serious, GRADE's terminology for rating down by three levels.

OBJECTIVES: The Grading of Recommendations Assessment, Development, and Evaluations (GRADE) system for assessing certainty in a body of evidence currently uses two levels, serious and very serious, for downgrading on a single domain. In the context of newer risk of bias instruments, such as Risk of Bias in Non-Randomized Studies I (ROBINS-I), evidence generated by nonrandomized studies may justify rating down by more than two levels on a single domain. Given the importance users of GRADE assign to terminology, our objective was to assess what term GRADE stakeholders would prefer for rating down certainty by three levels. STUDY DESIGN AND SETTING: We conducted a purposefully sampled online survey of GRADE stakeholders to assess possible terms including "critically serious," "extremely serious," "most serious," and "very, very serious" and conducted a descriptive and thematic analysis of responses. We then facilitated a GRADE working group workshop to generate consensus. RESULTS: A total of 225 respondents ranked and rated "extremely serious" highest, closely followed by "critically serious." Respondents felt that "extremely serious" was "more understandable" and "easiest to interpret". GRADE working group members described that the terms "extremely serious" appeared clearer and easier to translate in other languages. CONCLUSION: Based on this stakeholder-driven study, "extremely serious" is the preferred term to rate down certainty of evidence by three levels in the GRADE approach.

Sliding scale insulin for non-critically ill hospitalised adults with diabetes mellitus.

BACKGROUND: Diabetes mellitus is a metabolic disorder resulting from a defect in insulin secretion, function, or both. Hyperglycaemia in non-critically ill hospitalised people is associated with poor clinical outcomes (infections, prolonged hospital stay, poor wound healing, higher morbidity and mortality). In the hospital setting people diagnosed with diabetes receive insulin therapy as part of their treatment in order to achieve metabolic control. However, insulin therapy can be provided by different strategies (sliding scale insulin (SSI), basal-bolus insulin, and other modalities). Sliding scale insulin is currently the most commonly used method, however there is uncertainty about which strategy provides the best patient outcomes. OBJECTIVES: To assess the effects of SSI for non-critically ill hospitalised adults with diabetes mellitus. SEARCH METHODS: We identified eligible trials by searching MEDLINE, Embase, LILACS, and the Cochrane Library. We searched the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) and ClinicalTrials.gov trial registers. The date of the last search for all databases was December 2017. We also examined reference lists of identified randomised controlled trials (RCTs) and systematic reviews, and contacted trial authors. SELECTION CRITERIA: We included RCTs comparing SSI with other strategies for glycaemic control in non-critically ill hospitalised adult participants of any sex with diabetes mellitus. DATA COLLECTION AND ANALYSIS: Two review authors independently extracted data, assessed trials for risk of bias, and evaluated the overall certainty of evidence utilising the GRADE instrument. We synthesised data using a random-effects model meta-analysis with 95% prediction intervals, if possible, or descriptive analysis, as appropriate. MAIN RESULTS: Of 720 records screened, we included eight trials that randomised 1048 participants with type 2 diabetes (387 SSI participants and 615 participants in comparator groups were available for final analysis). We included non-critically ill medical and surgical adults with the diagnosis of diabetes mellitus. The mean follow-up time was measured by the mean length of hospital stay and ranged between five and 24 days. The mean age of participants was 44.5 years to 71 years.Overall, we judged the risk of bias on the trial level as unclear for selection bias, high for outcome-related performance and detection bias with regard to hypoglycaemic episodes, other adverse events, and mean glucose levels, and low for all-cause mortality and length of hospital stay. Attrition bias was low for all outcome measures.Six trials compared SSI with a basal-bolus insulin scheme, three of which investigating 64% of all participants in this category also applying an SSI approach in the bolus comparator part. One trial had a basal insulin-only comparator arm, and the remaining trial used continuous insulin infusion as the comparator. For our main comparison of SSI versus basal-bolus insulin, the results were as follows. Four trials reported mortality data. One out of 268 participants in the SSI group (0.3%) compared with two out of 334 participants in the basal-bolus group (0.6%) died (low-certainty evidence). Severe hypoglycaemic episodes, defined as blood glucose levels below 40 mg/dL (2.2 mmol/L), showed a risk ratio (RR) of 0.22, 95% confidence interval (CI) 0.05 to 1.00; P = 0.05; 5 trials; 667 participants; very low-certainty evidence. The 95% prediction interval ranged between 0.02 and 2.57. All nine severe hypoglycaemic episodes were observed among the 369 participants on basal-bolus insulin (2.4%). The mean length of hospital stay was 0.5 days longer for the SSI group, 95% CI -0.5 to 1.4; P = 0.32; 6 trials; 717 participants; very low-certainty evidence. The 95% prediction interval ranged between -1.7 days and 2.7 days. Adverse events other than hypoglycaemic episodes, such as postoperative infections, showed a RR of 1.16, 95% CI 0.25 to 5.37; P = 0.85; 3 trials; 481 participants; very low-certainty evidence. The mean blood glucose levels ranged across basal-bolus groups from 156 mg/dL (8.7 mmol/L) to 221 mg/dL (12.3 mmol/L). The mean blood glucose level in the SSI groups was 14.8 mg/dL (0.8 mmol/L) higher (95% CI 7.8 (0.4) to 21.8 (1.2); P < 0.001; 6 trials; 717 participants; low-certainty evidence). The 95% prediction interval ranged between -3.6 mg/dL (-0.2 mmol/L) and 33.2 mg/dL (1.8 mmol/L). No trial reported on diabetes-related mortality or socioeconomic effects. AUTHORS' CONCLUSIONS: We are uncertain which insulin strategy (SSI or basal-bolus insulin) is best for non-critically hospitalised adults with diabetes mellitus. A basal-bolus insulin strategy in these patients might result in better short-term glycaemic control but could increase the risk for severe hypoglycaemic episodes. The certainty of the body of evidence comparing SSI with basal-bolus insulin was low to very low and needs to be improved by adequately performed, well-powered RCTs in different hospital environments with well-educated medical staff using identical short-acting insulins in both intervention and comparator arms to compare the rigid SSI approach with flexible insulin application strategies.

Early Mobilization in Critically Ill Children: A Systematic Review.

OBJECTIVE: To characterize how early mobilization is defined in the published literature and describe the evidence on safety and efficacy on early mobilization in critically ill children. STUDY DESIGN: Systematic search of randomized and nonrandomized studies assessing early mobilization-based physical therapy in critically ill children under 18 years of age in MEDLINE, Embase, CINAHL, CENTRAL, the National Institutes of Health, Evidence in Pediatric Intensive Care Collaborative, Physiotherapy Evidence Database, and the Mobilization-Network. We extracted data to identify the types of mobility-based interventions and definitions for early, as well as barriers, feasibility, adverse events, and efficacy outcomes (mortality, morbidities, and length of stay). RESULTS: Of 1199 titles found, we included 11 studies (2 pilot trials and 9 observational studies) and 1 clinical practice guideline in the analyses. Neurodevelopmentally appropriate increasing mobility levels have been described for critically ill children, and "early" mobilization was defined as either a range (within 48-72 hours) from admission to the pediatric intensive care unit or when clinical safety criteria are met. Current evidence suggests that early mobilization is safe and feasible and institutional practice guidelines significantly increase the frequency of rehabilitation consults, improve the proportion of patients who receive early mobilization, and reduce the time to mobilization. However, there were inconsistencies in populations and interventions across studies, and imprecision and risk of bias in included studies that precluded us from pooling data to evaluate the efficacy outcomes of early mobilization. CONCLUSIONS: The definition of early mobilization varies, but seems to be feasible and safe in critically ill children. The efficacy for early mobilization in this population is yet undetermined because of the low certainty of the evidence available.

Smectite for acute infectious diarrhoea in children.

BACKGROUND: As mortality secondary to acute infectious diarrhoea has decreased worldwide, the focus shifts to adjuvant therapies to lessen the burden of disease. Smectite, a medicinal clay, could offer a complementary intervention to reduce the duration of diarrhoea. OBJECTIVES: To assess the effects of smectite for treating acute infectious diarrhoea in children. SEARCH METHODS: We searched the Cochrane Infectious Diseases Group Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Pubmed), Embase (Ovid), LILACS, reference lists from studies and previous reviews, and conference abstracts, up to 27 June 2017. SELECTION CRITERIA: Randomized and quasi-randomized trials comparing smectite to a control group in children aged one month to 18 years old with acute infectious diarrhoea. DATA COLLECTION AND ANALYSIS: Two review authors independently screened abstracts and the full texts for inclusion, extracted data, and assessed risk of bias. Our primary outcomes were duration of diarrhoea and clinical resolution at day 3. We summarized continuous outcomes using mean differences (MD) and dichotomous outcomes using risk ratios (RR), with 95% confidence intervals (CI). Where appropriate, we pooled data in meta-analyses and assessed heterogeneity. We explored publication bias using a funnel plot. MAIN RESULTS: Eighteen trials with 2616 children met our inclusion criteria. Studies were conducted in both ambulatory and in-hospital settings, and in both high-income and low- or middle-income countries. Most studies included children with rotavirus infections, and half included breastfed children.Smectite may reduce the duration of diarrhoea by approximately a day (MD -24.38 hours, 95% CI -30.91 to -17.85; 14 studies; 2209 children; low-certainty evidence); may increase clinical resolution at day 3 (risk ratio (RR) 2.10, 95% CI 1.30 to 3.39; 5 trials; 312 children; low-certainty evidence); and may reduce stool output (MD -11.37, 95% CI -21.94 to -0.79; 3 studies; 634 children; low-certainty evidence).We are uncertain whether smectite reduces stool frequency, measured as depositions per day (MD -1.33, 95% CI -2.28 to -0.38; 3 studies; 954 children; very low-certainty evidence). There was no evidence of an effect on need for hospitalization (RR 0.93, 95% CI 0.75 to 1.15; 2 studies; 885 children; low-certainty evidence) and need for intravenous rehydration (RR 0.77, 95% CI 0.54 to 1.11; 1 study; 81 children; moderate-certainty evidence). The most frequently reported side effect was constipation, which did not differ between groups (RR 4.71, 95% CI 0.56 to 39.19; 2 studies; 128 children; low-certainty evidence). No deaths or serious adverse effects were reported. AUTHORS' CONCLUSIONS: Based on low-certainty evidence, smectite used as an adjuvant to rehydration therapy may reduce the duration of diarrhoea in children with acute infectious diarrhoea by a day; may increase cure rate by day 3; and may reduce stool output, but has no effect on hospitalization rates or need for intravenous therapy.

A scoping review and survey provides the rationale, perceptions, and preferences for the integration of randomized and nonrandomized studies in evidence syntheses and GRADE assessments.

OBJECTIVES: To review the literature and obtain preferences and perceptions from experts regarding the role of randomized studies (RSs) and nonrandomized studies (NRSs) in systematic reviews of intervention effects. STUDY DESIGN AND SETTING: Scoping review and survey of experts. Using levels of certainty developed by the Grading of Recommendations Assessment, Development and Evaluation (GRADE) working group, experts expressed their preferences about the use of RS and NRS in health syntheses. RESULTS: Of 189 respondents, 123 had the expertise required to answer the questionnaire; 116 provided their extent of agreement with approaches to use NRS with RS. Most respondents would include NRS when RS was unfeasible (83.6%) or unethical (71.5%) and a majority to maximize the body of evidence (66.3%), compare results in NRS and RS (53.5%) and to identify subgroups (51.7%). Sizable minorities would include NRS and RS to address the effect of randomization (29.5%) or because the question being addressed was a public-health intervention (36.5%). In summary of findings tables, most respondents would include both bodies of evidence-in two rows in the same table-when RS provided moderate, low, or very-low certainty evidence; even when RS provided high certainty evidence, a sizable minority (25%) would still present results from both bodies of evidence. Very few (3.6%) would, under realistic circumstances, pool RS and NRS results. CONCLUSIONS: Most experts would include both RS and NRS in the same review under a wide variety of circumstances, but almost all would present results of two bodies of evidence separately.

Allergic Rhinitis and its Impact on Asthma (ARIA) guidelines-2016 revision.

BACKGROUND: Allergic rhinitis (AR) affects 10% to 40% of the population. It reduces quality of life and school and work performance and is a frequent reason for office visits in general practice. Medical costs are large, but avoidable costs associated with lost work productivity are even larger than those incurred by asthma. New evidence has accumulated since the last revision of the Allergic Rhinitis and its Impact on Asthma (ARIA) guidelines in 2010, prompting its update. OBJECTIVE: We sought to provide a targeted update of the ARIA guidelines. METHODS: The ARIA guideline panel identified new clinical questions and selected questions requiring an update. We performed systematic reviews of health effects and the evidence about patients' values and preferences and resource requirements (up to June 2016). We followed the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) evidence-to-decision frameworks to develop recommendations. RESULTS: The 2016 revision of the ARIA guidelines provides both updated and new recommendations about the pharmacologic treatment of AR. Specifically, it addresses the relative merits of using oral H1-antihistamines, intranasal H1-antihistamines, intranasal corticosteroids, and leukotriene receptor antagonists either alone or in combination. The ARIA guideline panel provides specific recommendations for the choice of treatment and the rationale for the choice and discusses specific considerations that clinicians and patients might want to review to choose the management most appropriate for an individual patient. CONCLUSIONS: Appropriate treatment of AR might improve patients' quality of life and school and work productivity. ARIA recommendations support patients, their caregivers, and health care providers in choosing the optimal treatment.

Use of chewing gum in children undergoing an appendectomy: A randomized clinical controlled trial.

INTRODUCTION: Post-operative ileus is a common condition among pediatric patients undergoing appendectomy. We aim to assess the feasibility, safety, and effectiveness of chewing gum to reduce ileus, and decrease time to oral tolerance. METHODS: A randomized trial was conducted in 5-18 year old patients that underwent an appendectomy. Subjects in the intervention group received sugar-free chewing gum within the first 12 h after surgery and control group received the usual therapy. We assessed the acceptability of the intervention, time to pass first flatus, present first bowel movement, and time to tolerate oral intake. RESULTS: A total of 41 patients were recruited, 21 in the intervention group and 20 in the control group. Mean time (SD) to first flatus in the intervention group was 17.18 h (8.18), and 24.37 h (17.53) in the control group (mean difference [MD] of -7.19 h; 95% CI, -15.7 to 1.38). Time to first bowel movement (MD, -4.6 h, 95%CI -18.5 to 9.3), time to tolerate oral intake (MD, 4.17 h; 95%CI -9.2 to 17.5), and length of hospital stay (MD, 6.9 h, 95%CI -19.1 to 33.1) appeared not to be affected by the intervention. Chewing gum was accepted, well tolerated, and without complications. DISCUSSION: The use of chewing gum in children undergoing an appendectomy was safe and well tolerated and might lead to a faster recovery of bowel function, more studies are needed to prove if length of hospital stay and other outcomes are improved.

World Allergy Organization-McMaster University Guidelines for Allergic Disease Prevention (GLAD-P): Vitamin D.

BACKGROUND: The prevalence of allergic diseases is approximately 10 % in infants whose parents and siblings do not have allergic diseases and 20-30 % in those with an allergic first-degree relative. Vitamin D is involved in the regulation of the immune system and it may play a role in the development, severity and course of asthma and other allergic diseases. OBJECTIVE: The World Allergy Organization (WAO) convened a guideline panel to develop evidence-based recommendations addressing the use of vitamin D in primary prevention of allergic diseases. METHODS: Our WAO guideline panel identified the most relevant clinical questions and performed a systematic review of randomized controlled trials and non-randomized studies (NRS), specifically cohort and case-control studies, of vitamin D supplementation for the prevention of allergic diseases. We also reviewed the evidence about values and preferences, and resource requirements (up to January 2015, with an update on January 30, 2016). We followed the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to develop recommendations. RESULTS: Having reviewed the currently available evidence, the WAO guideline panel found no support for the hypothesis that vitamin D supplementation reduces the risk of developing allergic diseases in children. The WAO guideline panel suggest not using vitamin D in pregnant women, breastfeeding mothers, or healthy term infants as a means of preventing the development of allergic diseases. This recommendation does not apply to those mothers and infants who have other indications for prophylactic or therapeutic use of vitamin D. The panel's recommendations are conditional and supported by very low certainty evidence. CONCLUSIONS: WAO recommendations about vitamin D supplementation for the prevention of allergic diseases support parents, clinicians and other health care professionals in their decisions whether or not to use vitamin D in preventing allergic diseases in healthy, term infants.