shaPRS: Leveraging shared genetic effects across traits or ancestries improves accuracy of polygenic scores.

We present shaPRS, a method that leverages widespread pleiotropy between traits or shared genetic effects across ancestries, to improve the accuracy of polygenic scores. The method uses genome-wide summary statistics from two diseases or ancestries to improve the genetic effect estimate and standard error at SNPs where there is homogeneity of effect between the two datasets. When there is significant evidence of heterogeneity, the genetic effect from the disease or population closest to the target population is maintained. We show via simulation and a series of real-world examples that shaPRS substantially enhances the accuracy of polygenic risk scores (PRSs) for complex diseases and greatly improves PRS performance across ancestries. shaPRS is a PRS pre-processing method that is agnostic to the actual PRS generation method, and as a result, it can be integrated into existing PRS generation pipelines and continue to be applied as more performant PRS methods are developed over time.

Early versus persistent Complex Regional Pain Syndrome: Is there a difference in patient reported outcomes following rehabilitation?

BACKGROUND: Expert consensus asserts that early treatment of Complex Regional Pain Syndrome (CRPS) leads to better outcomes. Yet no evidence supports this assumption regarding the recognized gold standard of multidisciplinary functional rehabilitation. To address this, we aimed to establish if there is a difference in outcomes between early CRPS (<1 year symptom duration) and persistent CRPS (= >1 year symptom duration) following rehabilitation and whether any gains are maintained at three months. METHOD: Secondary analysis was conducted on previously collected clinical Patient Reported Outcome Measures (PROMS) data from 218 patients attending a residential multidisciplinary rehabilitation programme. Datasets were categorized into early CRPS (n = 40) or persistent CRPS (n = 178) dependent on symptom duration. Function, pain, self-efficacy, kinesiophobia and psychological health domains were compared using repeated measures analysis of covariance for a two group design for group difference post rehabilitation and at three month follow-up. RESULTS: Post-rehabilitation, both groups improved in pain, function, kinesiophobia, psychological health and self-efficacy. At three months, the persistent CRPS group maintained improvements in pain and function. This was not achieved in early CRPS. CONCLUSION: This exploratory study is the first to empirically test the assumption that those with early CRPS have better outcomes following rehabilitation. Our clinical data challenges this, as both early and persistent CRPS groups improved following rehabilitation. Findings indicate that rehabilitation benefits those with CRPS, regardless of symptom duration. However, unlike early CRPS, those with persistent CRPS sustain gains at follow-up. Further prospective exploration is warranted. SIGNIFICANCE: Expert consensus recommends early treatment for Complex Regional Pain Syndrome, yet there is little empirical evidence to support this. Our findings are the first to challenge this assumption by revealing no difference in outcomes between early and persistent CRPS post-rehabilitation. However, those with persistent CRPS maintain gains after three months, unlike people with early CRPS (symptoms < one year). These findings are relevant to clinical practice as they challenge established assumptions, suggesting a focus on improving early CRPS follow-up outcomes.

Vitamin D for the treatment of inflammatory bowel disease.

BACKGROUND: Vitamin D possesses immunomodulatory properties and has been implicated in the pathogenesis and severity of inflammatory bowel disease (IBD). Animal studies and emerging epidemiological evidence have demonstrated an association between vitamin D deficiency and worse disease activity. However, the role of vitamin D for the treatment of IBD is unclear. OBJECTIVES: To evaluate the benefits and harms of vitamin D supplementation as a treatment for IBD. SEARCH METHODS: We used standard, extensive Cochrane search methods. The latest search date was Jun 2023. SELECTION CRITERIA: We included randomised controlled trials (RCTs) in people of all ages with active or inactive IBD comparing any dose of vitamin D with another dose of vitamin D, another intervention, placebo, or no intervention. We defined doses as: vitamin D (all doses), any-treatment-dose vitamin D (greater than 400 IU/day), high-treatment-dose vitamin D (greater than 1000 IU/day), low-treatment-dose vitamin D (400 IU/day to 1000 IU/day), and supplemental-dose vitamin D (less than 400 IU/day). DATA COLLECTION AND ANALYSIS: We used standard Cochrane methods. Our primary outcomes were 1. clinical response for people with active disease, 2. clinical relapse for people in remission, 3. quality of life, and 4. withdrawals due to adverse events. Our secondary outcomes were 5. disease activity at end of study, 6. normalisation of vitamin D levels at end of study, and 7. total serious adverse events. We used GRADE to assess certainty of evidence for each outcome. MAIN RESULTS: We included 22 RCTs with 1874 participants. Study duration ranged from four to 52 weeks. Ten studies enroled people with Crohn's disease (CD), five enroled people with ulcerative colitis (UC), and seven enroled people with CD and people with UC. Seventeen studies included adults, three included children, and two included both. Four studies enroled people with active disease, six enroled people in remission, and 12 enroled both. We assessed each study for risk of bias across seven individual domains. Five studies were at low risk of bias across all seven domains. Ten studies were at unclear risk of bias in at least one domain but with no areas of high risk of bias. Seven studies were at high risk of bias for blinding of participants and assessors. Vitamin D (all doses) versus placebo or no treatment Thirteen studies compared vitamin D against placebo or no treatment. We could not draw any conclusions on clinical response for UC as the certainty of the evidence was very low (risk ratio (RR) 4.00, 95% confidence interval (CI) 1.51 to 10.57; 1 study, 60 participants). There were no data on CD. There may be fewer clinical relapses for IBD when using vitamin D compared to placebo or no treatment (RR 0.57, 95% CI 0.34 to 0.96; 3 studies, 310 participants). The certainty of the evidence was low. We could not draw any conclusions on quality of life for IBD (standardised mean difference (SMD) -0.13, 95% CI -3.10 to 2.83 (the SMD value indicates a negligent decrease in quality of life, and the corresponding CIs indicate that the effect can range from a large decrease to a large increase in quality of life); 2 studies, 243 participants) or withdrawals due to adverse events for IBD (RR 1.97, 95% CI 0.18 to 21.27; 12 studies, 1251 participants; note 11 studies reported withdrawals but recorded 0 events in both groups. Thus, the RR and CIs were calculated from 1 study rather than 12). The certainty of the evidence was very low. High-treatment-dose vitamin D versus low-treatment-dose vitamin D Five studies compared high treatment vitamin D doses against low treatment vitamin D doses. There were no data on clinical response. There may be no difference in clinical relapse for CD (RR 0.48, 95% CI 0.23 to 1.01; 1 study, 34 participants). The certainty of the evidence was low. We could not draw any conclusions on withdrawals due to adverse events for IBD as the certainty of the evidence was very low (RR 0.89, 95% CI 0.06 to 13.08; 3 studies, 104 participants; note 2 studies reported withdrawals but recorded 0 events in both groups. Thus, the RR and CIs were calculated from 1 study rather than 3). The data on quality of life and disease activity could not be meta-analysed, were of very low certainty, and no conclusions could be drawn. Any-treatment-dose vitamin D versus supplemental-dose vitamin D Four studies compared treatment doses of vitamin D against supplemental doses. There were no data on clinical response and relapse. There were no data on quality of life that could be meta-analysed. We could not draw any conclusions on withdrawals due to adverse events for IBD as the certainty of the evidence was very low (RR 3.09, 95% CI 0.13 to 73.17; 4 studies, 233 participants; note 3 studies reported withdrawals but recorded 0 events in both groups. Thus, the RR and CIs were calculated from 1 study rather than 4). AUTHORS' CONCLUSIONS: There may be fewer clinical relapses when comparing vitamin D with placebo, but we cannot draw any conclusions on differences in clinical response, quality of life, or withdrawals, due to very low-certainty evidence. When comparing high and low doses of vitamin D, there were no data for clinical response, but there may be no difference in relapse for CD. We cannot draw conclusions on the other outcomes due to very low certainty evidence. Finally, comparing vitamin D (all doses) to supplemental-dose vitamin D, there were no data on clinical relapse or response, and we could not draw conclusions on other outcomes due to very low certainty evidence or missing data. It is difficult to make any clear recommendations for future research on the basis of the findings of this review. Future studies must be clear on the baseline populations, the purpose of vitamin D treatment, and, therefore, study an appropriate dosing strategy. Stakeholders in the field may wish to reach consensus on such issues prior to new studies.

Accurate detection of shared genetic architecture from GWAS summary statistics in the small-sample context.

Assessment of the genetic similarity between two phenotypes can provide insight into a common genetic aetiology and inform the use of pleiotropy-informed, cross-phenotype analytical methods to identify novel genetic associations. The genetic correlation is a well-known means of quantifying and testing for genetic similarity between traits, but its estimates are subject to comparatively large sampling error. This makes it unsuitable for use in a small-sample context. We discuss the use of a previously published nonparametric test of genetic similarity for application to GWAS summary statistics. We establish that the null distribution of the test statistic is modelled better by an extreme value distribution than a transformation of the standard exponential distribution. We show with simulation studies and real data from GWAS of 18 phenotypes from the UK Biobank that the test is to be preferred for use with small sample sizes, particularly when genetic effects are few and large, outperforming the genetic correlation and another nonparametric statistical test of independence. We find the test suitable for the detection of genetic similarity in the rare disease context.

BBmix: a Bayesian beta-binomial mixture model for accurate genotyping from RNA-sequencing.

MOTIVATION: While many pipelines have been developed for calling genotypes using RNA-sequencing (RNA-Seq) data, they all have adapted DNA genotype callers that do not model biases specific to RNA-Seq such as allele-specific expression (ASE). RESULTS: Here, we present Bayesian beta-binomial mixture model (BBmix), a Bayesian beta-binomial mixture model that first learns the expected distribution of read counts for each genotype, and then deploys those learned parameters to call genotypes probabilistically. We benchmarked our model on a wide variety of datasets and showed that our method generally performed better than competitors, mainly due to an increase of up to 1.4% in the accuracy of heterozygous calls, which may have a big impact in reducing false positive rate in applications sensitive to genotyping error such as ASE. Moreover, BBmix can be easily incorporated into standard pipelines for calling genotypes. We further show that parameters are generally transferable within datasets, such that a single learning run of less than 1 h is sufficient to call genotypes in a large number of samples. AVAILABILITY AND IMPLEMENTATION: We implemented BBmix as an R package that is available for free under a GPL-2 licence at https://gitlab.com/evigorito/bbmix and https://cran.r-project.org/package=bbmix with accompanying pipeline at https://gitlab.com/evigorito/bbmix_pipeline.

Probiotics for management of functional abdominal pain disorders in children.

BACKGROUND: Functional abdominal pain is pain occurring in the abdomen that cannot be fully explained by another medical condition and is common in children. It has been hypothesised that the use of micro-organisms, such as probiotics and synbiotics (a mixture of probiotics and prebiotics), might change the composition of bacterial colonies in the bowel and reduce inflammation, as well as promote normal gut physiology and reduce functional symptoms. OBJECTIVES: To assess the efficacy and safety of probiotics in the treatment of functional abdominal pain disorders in children. SEARCH METHODS: We searched MEDLINE, Embase, the Cochrane Central Register of Controlled Trials (CENTRAL) and two clinical trials registers from inception to October 2021. SELECTION CRITERIA: Randomised controlled trials (RCTs) that compare probiotic preparations (including synbiotics) to placebo, no treatment or any other interventional preparation in patients aged between 4 and 18 years of age with a diagnosis of functional abdominal pain disorder according to the Rome II, Rome III or Rome IV criteria. DATA COLLECTION AND ANALYSIS: The primary outcomes were treatment success as defined by the primary studies, complete resolution of pain, improvement in the severity of pain and improvement in the frequency of pain. Secondary outcomes included serious adverse events, withdrawal due to adverse events, adverse events, school performance or change in school performance or attendance, social and psychological functioning or change in social and psychological functioning, and quality of life or change in quality life measured using any validated scoring tool. For dichotomous outcomes, we calculated the risk ratio (RR) and corresponding 95% confidence interval (95% CI). For continuous outcomes, we calculated the mean difference (MD) and corresponding 95% CI. MAIN RESULTS: We included 18 RCTs assessing the effectiveness of probiotics and synbiotics in reducing the severity and frequency of pain, involving a total of 1309 patients. Probiotics may achieve more treatment success when compared with placebo at the end of the treatment, with 50% success in the probiotic group versus 33% success in the placebo group (RR 1.57, 95% CI 1.05 to 2.36; 554 participants; 6 studies; I2 = 70%; low-certainty evidence).  It is not clear whether probiotics are more effective than placebo for complete resolution of pain, with 42% success in the probiotic group versus 27% success in the placebo group (RR 1.55, 95% CI 0.94 to 2.56; 460 participants; 6 studies; I2 = 70%; very low-certainty evidence). We judged the evidence to be of very low certainty due to high inconsistency and risk of bias. We were unable to draw meaningful conclusions from our meta-analyses of the pain severity and pain frequency outcomes due to very high unexplained heterogeneity leading to very low-certainty evidence. None of the included studies reported serious adverse events. Meta-analysis showed no difference in withdrawals due to adverse events between probiotics (1/275) and placebo (1/269) (RR 1.00, 95% CI 0.07 to 15.12). The results were identical for the total patients with any reported adverse event outcome. However, these results are of very low certainty due to imprecision from the very low numbers of events and risk of bias. Synbiotics may result in more treatment success at study end when compared with placebo, with 47% success in the probiotic group versus 35% success in the placebo group (RR 1.34, 95% CI 1.03 to 1.74; 310 participants; 4 studies; I2 = 0%; low certainty). One study used Bifidobacterium coagulans/fructo-oligosaccharide, one used Bifidobacterium lactis/inulin, one used Lactobacillus rhamnosus GG/inulin and in one study this was not stated).  Synbiotics may result in little difference in complete resolution of pain at study end when compared with placebo, with 52% success in the probiotic group versus 32% success in the placebo group (RR 1.65, 95% CI 0.97 to 2.81; 131 participants; 2 studies; I2 = 18%; low-certainty evidence). We were unable to draw meaningful conclusions from our meta-analyses of pain severity or frequency of pain due to very high unexplained heterogeneity leading to very low-certainty evidence.  None of the included studies reported serious adverse events. Meta-analysis showed little to no difference in withdrawals due to adverse events between synbiotics (8/155) and placebo (1/147) (RR 4.58, 95% CI 0.80 to 26.19), or in any reported adverse events (3/96 versus 1/93, RR 2.88, 95% CI 0.32 to 25.92). These results are of very low certainty due to imprecision from the very low numbers of events and risk of bias. There were insufficient data to analyse by subgroups of specific functional abdominal pain syndrome (irritable bowel syndrome, functional dyspepsia, abdominal migraine, functional abdominal pain - not otherwise specified) or by specific strain of probiotic. There was insufficient evidence on school performance or change in school performance/attendance, social and psychological functioning, or quality of life to draw conclusions about the effects of probiotics or synbiotics on these outcomes. AUTHORS' CONCLUSIONS: The results from this review demonstrate that probiotics and synbiotics may be more efficacious than placebo in achieving treatment success, but the evidence is of low certainty. The evidence demonstrates little to no difference between probiotics or synbiotics and placebo in complete resolution of pain. We were unable to draw meaningful conclusions about the impact of probiotics or synbiotics on the frequency and severity of pain as the evidence was all of very low certainty due to significant unexplained heterogeneity or imprecision. There were no reported cases of serious adverse events when using probiotics or synbiotics amongst the included studies, although a review of RCTs may not be the best context to assess long-term safety. The available evidence on adverse effects was of very low certainty and no conclusions could be made in this review. Safety will always be a priority in paediatric populations when considering any treatment. Reporting of all adverse events, adverse events needing withdrawal, serious adverse events and, particularly, long-term safety outcomes are vital to meaningfully move forward the evidence base in this field. Further targeted and appropriately designed RCTs are needed to address the gaps in the evidence base. In particular, appropriate powering of studies to confirm the safety of specific strains not yet investigated and studies to investigate long-term follow-up of patients are both warranted.

A genome-wide association study suggests new susceptibility loci for primary antiphospholipid syndrome.

Objectives: Primary antiphospholipid syndrome (PAPS) is a rare autoimmune disease characterized by the presence of antiphospholipid antibodies and the occurrence of thrombotic events and pregnancy complications. Our study aimed to identify novel genetic susceptibility loci associated with PAPS. Methods: We performed a genome-wide association study comprising 5,485 individuals (482 affected individuals) of European ancestry. Significant and suggestive independent variants from a meta-analysis of approximately 7 million variants were evaluated for functional and biological process enrichment. The genetic risk variability for PAPS in different populations was also assessed. Hierarchical clustering, Mahalanobis distance, and Dirichlet Process Mixtures with uncertainty clustering methods were used to assess genetic similarities between PAPS and other immune-mediated diseases. Results: We revealed genetic associations with PAPS in a regulatory locus within the HLA class II region near HLA-DRA and in STAT4 with a genome-wide level of significance. 34 additional suggestive genetic susceptibility loci for PAPS were also identified. The disease risk allele in the HLA class II locus is associated with overexpression of HLA-DRB6 , HLA-DRB9 , HLA-DPB2 , HLA-DQA2 and HLA-DQB2 , and is independent of the association between PAPS and HLA-DRB1*1302 . Functional analyses highlighted immune and nervous system related pathways in PAPS-associated loci. The comparison with other immune-mediated diseases revealed a close genetic relatedness to neuromyelitis optica, systemic sclerosis, and Sjögren's syndrome, suggesting colocalized causal variations close to STAT4 , TNPO3 , and BLK . Conclusions: This study represents a comprehensive large-scale genetic analysis for PAPS and provides new insights into the genetic basis and pathophysiology of this rare disease.

Consensus clustering for Bayesian mixture models.

BACKGROUND: Cluster analysis is an integral part of precision medicine and systems biology, used to define groups of patients or biomolecules. Consensus clustering is an ensemble approach that is widely used in these areas, which combines the output from multiple runs of a non-deterministic clustering algorithm. Here we consider the application of consensus clustering to a broad class of heuristic clustering algorithms that can be derived from Bayesian mixture models (and extensions thereof) by adopting an early stopping criterion when performing sampling-based inference for these models. While the resulting approach is non-Bayesian, it inherits the usual benefits of consensus clustering, particularly in terms of computational scalability and providing assessments of clustering stability/robustness. RESULTS: In simulation studies, we show that our approach can successfully uncover the target clustering structure, while also exploring different plausible clusterings of the data. We show that, when a parallel computation environment is available, our approach offers significant reductions in runtime compared to performing sampling-based Bayesian inference for the underlying model, while retaining many of the practical benefits of the Bayesian approach, such as exploring different numbers of clusters. We propose a heuristic to decide upon ensemble size and the early stopping criterion, and then apply consensus clustering to a clustering algorithm derived from a Bayesian integrative clustering method. We use the resulting approach to perform an integrative analysis of three 'omics datasets for budding yeast and find clusters of co-expressed genes with shared regulatory proteins. We validate these clusters using data external to the analysis. CONCLUSTIONS: Our approach can be used as a wrapper for essentially any existing sampling-based Bayesian clustering implementation, and enables meaningful clustering analyses to be performed using such implementations, even when computational Bayesian inference is not feasible, e.g. due to poor exploration of the target density (often as a result of increasing numbers of features) or a limited computational budget that does not along sufficient samples to drawn from a single chain. This enables researchers to straightforwardly extend the applicability of existing software to much larger datasets, including implementations of sophisticated models such as those that jointly model multiple datasets.

fcfdr: an R package to leverage continuous and binary functional genomic data in GWAS.

BACKGROUND: Genome-wide association studies (GWAS) are limited in power to detect associations that exceed the stringent genome-wide significance threshold. This limitation can be alleviated by leveraging relevant auxiliary data, such as functional genomic data. Frameworks utilising the conditional false discovery rate have been developed for this purpose, and have been shown to increase power for GWAS discovery whilst controlling the false discovery rate. However, the methods are currently only applicable for continuous auxiliary data and cannot be used to leverage auxiliary data with a binary representation, such as whether SNPs are synonymous or non-synonymous, or whether they reside in regions of the genome with specific activity states. RESULTS: We describe an extension to the cFDR framework for binary auxiliary data, called "Binary cFDR". We demonstrate FDR control of our method using detailed simulations, and show that Binary cFDR performs better than a comparator method in terms of sensitivity and FDR control. We introduce an all-encompassing user-oriented CRAN R package ( https://annahutch.github.io/fcfdr/ ; https://cran.r-project.org/web/packages/fcfdr/index.html ) and demonstrate its utility in an application to type 1 diabetes, where we identify additional genetic associations. CONCLUSIONS: Our all-encompassing R package, fcfdr, serves as a comprehensive toolkit to unite GWAS and functional genomic data in order to increase statistical power to detect genetic associations.

Use of MRP8/14 in clinical practice as a predictor of outcome after methotrexate withdrawal in patients with juvenile idiopathic arthritis.

The objective of this study was to determine the effectiveness of MRP8/14 as a predictor of disease flare in patients with juvenile idiopathic arthritis (JIA) following the withdrawal of methotrexate (MTX) in a routine clinical setting. All MRP8/14 tests performed at a single centre in a 27-month period were considered for analysis. Patients were assessed against criteria for inactive disease and subsequent disease flare. Decisions on whether or not to stop treatment were recorded. MRP8/14 results were assessed in conjunction with clinical information. Clinicians were also surveyed to investigate if MRP8/14 influenced their decision to discontinue MTX where this was available at that time point. One hundred four cases met the inclusion criteria during the study period. Although there was no significant difference in flares between patients with an elevated or low MRP8/14 value, in those who stopped MTX (n = 22), no patients with a low MRP8/14 (≤ 4000 ng/ml) result flared (follow-up time 12 months). Clinicians reported that for patients with clinically inactive disease and an elevated MRP8/14 result (> 4000 ng/ml), none would advise withdrawal of MTX. Low MRP8/14 was interpreted favourably when considering stopping MTX treatment in patients with JIA. Implementation of MRP8/14 testing has changed clinical practice at this centre. However, the observation that some patients in our cohort who had an elevated MRP8/14 value did not flare after stopping MTX for non-disease-related reasons highlights the need for further biomarkers to predict the risk of flare off medication in JIA and aid clinicians in treatment decisions. Key Points • First study of serum MRP8/14 measurement in clinical practice to inform treatment decisions in patients with JIA. • No patients with a low MRP8/14 test result went on to suffer a disease flare in 12 months of follow follow-up. • Further biomarkers are needed to predict the risk of flare off medication in JIA and treatment decisions.

Combining evidence from Mendelian randomization and colocalization: Review and comparison of approaches.

Mendelian randomization and colocalization are two statistical approaches that can be applied to summarized data from genome-wide association studies (GWASs) to understand relationships between traits and diseases. However, despite similarities in scope, they are different in their objectives, implementation, and interpretation, in part because they were developed to serve different scientific communities. Mendelian randomization assesses whether genetic predictors of an exposure are associated with the outcome and interprets an association as evidence that the exposure has a causal effect on the outcome, whereas colocalization assesses whether two traits are affected by the same or distinct causal variants. When considering genetic variants in a single genetic region, both approaches can be performed. While a positive colocalization finding typically implies a non-zero Mendelian randomization estimate, the reverse is not generally true: there are several scenarios which would lead to a non-zero Mendelian randomization estimate but lack evidence for colocalization. These include the existence of distinct but correlated causal variants for the exposure and outcome, which would violate the Mendelian randomization assumptions, and a lack of strong associations with the outcome. As colocalization was developed in the GWAS tradition, typically evidence for colocalization is concluded only when there is strong evidence for associations with both traits. In contrast, a non-zero estimate from Mendelian randomization can be obtained despite only nominally significant genetic associations with the outcome at the locus. In this review, we discuss how the two approaches can provide complementary information on potential therapeutic targets.

Probiotics for treatment of chronic constipation in children.

BACKGROUND: Functional constipation is defined as chronic constipation with no identifiable underlying cause. It is a significant cause of morbidity in children, accounting for up to 25% of visits to paediatric gastroenterologists. Probiotic preparations may sufficiently alter the gut microbiome and promote normal gut physiology in a way that helps relieve functional constipation. Several studies have sought to address this hypothesis, as well as the role of probiotics in other functional gut disorders. Therefore, it is important to have a focused review to assess the evidence to date. OBJECTIVES: To evaluate the efficacy and safety of probiotics for the management of chronic constipation without a physical explanation in children. SEARCH METHODS: On 28 June 2021, we searched CENTRAL, MEDLINE, Embase, CINAHL, AMED, WHO ICTR, and ClinicalTrials.gov, with no language, date, publication status, or document type limitations. SELECTION CRITERIA: We included randomised controlled trials (RCTs) that assessed probiotic preparations (including synbiotics) compared to placebo, no treatment or any other interventional preparation in people aged between 0 and 18 years old with a diagnosis of functional constipation according to consensus criteria (such as Rome IV). DATA COLLECTION AND ANALYSIS: We used standard methodological procedures expected by Cochrane. MAIN RESULTS: We included 14 studies (1127 randomised participants): 12 studies assessed probiotics in the treatment of functional constipation, whilst two studies investigated synbiotic preparations. Three studies compared probiotics to placebo in relation to the frequency of defecation at study end, but we did not pool them as there was very significant unexplained heterogeneity. Four studies compared probiotics to placebo in relation to treatment success. There may be no difference in global improvement/treatment success (RR 1.29, 95% CI 0.73 to 2.26; 313 participants; low-certainty evidence). Five studies compared probiotics to placebo in relation to withdrawals due to adverse events, with the pooled effect suggesting there may be no difference (RR 0.64, 95% CI 0.21 to 1.95; 357 participants; low-certainty evidence). The pooled estimate from three studies that compared probiotics plus an osmotic laxative to osmotic laxative alone found there may be no difference in frequency of defecation (MD -0.01, 95% CI -0.57 to 0.56; 268 participants; low-certainty evidence). Two studies compared probiotics plus an osmotic laxative to osmotic laxative alone in relation to global improvement/treatment success, and found there may be no difference between the treatments (RR 0.95, 95% CI 0.79 to 1.15; 139 participants; low-certainty evidence). Three studies compared probiotics plus osmotic laxative to osmotic laxative alone in relation to withdrawals due to adverse events, but it is unclear if there is a difference between them (RR 2.86, 95% CI 0.12 to 68.35; 268 participants; very low-certainty evidence). Two studies compared probiotics versus magnesium oxide. It is unclear if there is a difference in frequency of defecation (MD 0.28, 95% CI -0.58 to 1.14; 36 participants), treatment success (RR 1.08, 95% CI 0.74 to 1.57; 36 participants) or withdrawals due to adverse events (RR 0.50, 95% CI 0.05 to 5.04; 77 participants). The certainty of the evidence is very low for these outcomes. One study assessed the role of a synbiotic preparation in comparison to placebo. There may be higher treatment success in favour of synbiotics compared to placebo (RR 2.32, 95% CI 1.54 to 3.47; 155 participants; low-certainty evidence). The study reported that there were no withdrawals due to adverse effects in either group. One study assessed a synbiotic plus paraffin compared to paraffin alone. It is uncertain if there is a difference in frequency of defecation (MD 0.74, 95% CI -0.96, 2.44; 66 participants; very low-certainty evidence), or treatment success (RR 0.91, 95% CI 0.71 to 1.17; 66 participants; very low-certainty evidence). The study reported that there were no withdrawals due to adverse effects in either group. One study compared a synbiotic preparation to paraffin. It is uncertain if there is a difference in frequency of defecation (MD -1.53, 95% CI -3.00, -0.06; 60 participants; very low-certainty evidence) or in treatment success (RR 0.86, 95% CI 0.65, 1.13; 60 participants; very low-certainty evidence). The study reported that there were no withdrawals due to adverse effects in either group. All secondary outcomes were either not reported or reported in a way that did not allow for analysis. AUTHORS' CONCLUSIONS: There is insufficient evidence to conclude whether probiotics are efficacious in successfully treating chronic constipation without a physical explanation in children or changing the frequency of defecation, or whether there is a difference in withdrawals due to adverse events when compared with placebo. There is limited evidence from one study to suggest a synbiotic preparation may be more likely than placebo to lead to treatment success, with no difference in withdrawals due to adverse events. There is insufficient evidence to draw efficacy or safety conclusions about the use of probiotics in combination with or in comparison to any of the other interventions reported. The majority of the studies that presented data on serious adverse events reported that no events occurred. Two studies did not report this outcome. Future studies are needed to confirm efficacy, but the research community requires guidance on the best context for probiotics in such studies, considering where they should be best considered in a potential treatment hierarchy and should align with core outcome sets to support future interpretation of findings.

Autoimmunity Is a Significant Feature of Idiopathic Pulmonary Arterial Hypertension.

Rationale: Autoimmunity is believed to play a role in idiopathic pulmonary arterial hypertension (IPAH). It is not clear whether this is causative or a bystander of disease and if it carries any prognostic or treatment significance. Objectives: To study autoimmunity in IPAH using a large cross-sectional cohort. Methods: Assessment of the circulating immune cell phenotype was undertaken using flow cytometry, and the profile of serum immunoglobulins was generated using a standardized multiplex array of 19 clinically validated autoantibodies in 473 cases and 946 control subjects. Additional glutathione S-transferase fusion array and ELISA data were used to identify a serum autoantibody to BMPR2 (bone morphogenetic protein receptor type 2). Clustering analyses and clinical correlations were used to determine associations between immunogenicity and clinical outcomes. Measurements and Main Results: Flow cytometric immune profiling demonstrates that IPAH is associated with an altered humoral immune response in addition to raised IgG3. Multiplexed autoantibodies were significantly raised in IPAH, and clustering demonstrated three distinct clusters: "high autoantibody," "low autoantibody," and a small "intermediate" cluster exhibiting high concentrations of ribonucleic protein complex. The high-autoantibody cluster had worse hemodynamics but improved survival. A small subset of patients demonstrated immunoglobulin reactivity to BMPR2. Conclusions: This study establishes aberrant immune regulation and presence of autoantibodies as key features in the profile of a significant proportion of patients with IPAH and is associated with clinical outcomes.

Probabilistic classification of anti-SARS-CoV-2 antibody responses improves seroprevalence estimates.

Objectives: Population-level measures of seropositivity are critical for understanding the epidemiology of an emerging pathogen, yet most antibody tests apply a strict cutoff for seropositivity that is not learnt in a data-driven manner, leading to uncertainty when classifying low-titer responses. To improve upon this, we evaluated cutoff-independent methods for their ability to assign likelihood of SARS-CoV-2 seropositivity to individual samples. Methods: Using robust ELISAs based on SARS-CoV-2 spike (S) and the receptor-binding domain (RBD), we profiled antibody responses in a group of SARS-CoV-2 PCR+ individuals (n = 138). Using these data, we trained probabilistic learners to assign likelihood of seropositivity to test samples of unknown serostatus (n = 5100), identifying a support vector machines-linear discriminant analysis learner (SVM-LDA) suited for this purpose. Results: In the training data from confirmed ancestral SARS-CoV-2 infections, 99% of participants had detectable anti-S and -RBD IgG in the circulation, with titers differing > 1000-fold between persons. In data of otherwise healthy individuals, 7.2% (n = 367) of samples were of uncertain serostatus, with values in the range of 3-6SD from the mean of pre-pandemic negative controls (n = 595). In contrast, SVM-LDA classified 6.4% (n = 328) of test samples as having a high likelihood (> 99% chance) of past infection, 4.5% (n = 230) to have a 50-99% likelihood, and 4.0% (n = 203) to have a 10-49% likelihood. As different probabilistic approaches were more consistent with each other than conventional SD-based methods, such tools allow for more statistically-sound seropositivity estimates in large cohorts. Conclusion: Probabilistic antibody testing frameworks can improve seropositivity estimates in populations with large titer variability.

Mendelian randomization.

Mendelian randomization (MR) is a term that applies to the use of genetic variation to address causal questions about how modifiable exposures influence different outcomes. The principles of MR are based on Mendel's laws of inheritance and instrumental variable estimation methods, which enable the inference of causal effects in the presence of unobserved confounding. In this Primer, we outline the principles of MR, the instrumental variable conditions underlying MR estimation and some of the methods used for estimation. We go on to discuss how the assumptions underlying an MR study can be assessed and give methods of estimation that are robust to certain violations of these assumptions. We give examples of a range of studies in which MR has been applied, the limitations of current methods of analysis and the outlook for MR in the future. The difference between the assumptions required for MR analysis and other forms of non-interventional epidemiological studies means that MR can be used as part of a triangulation across multiple sources of evidence for causal inference.

Leveraging auxiliary data from arbitrary distributions to boost GWAS discovery with Flexible cFDR.

Genome-wide association studies (GWAS) have identified thousands of genetic variants that are associated with complex traits. However, a stringent significance threshold is required to identify robust genetic associations. Leveraging relevant auxiliary covariates has the potential to boost statistical power to exceed the significance threshold. Particularly, abundant pleiotropy and the non-random distribution of SNPs across various functional categories suggests that leveraging GWAS test statistics from related traits and/or functional genomic data may boost GWAS discovery. While type 1 error rate control has become standard in GWAS, control of the false discovery rate can be a more powerful approach. The conditional false discovery rate (cFDR) extends the standard FDR framework by conditioning on auxiliary data to call significant associations, but current implementations are restricted to auxiliary data satisfying specific parametric distributions, typically GWAS p-values for related traits. We relax these distributional assumptions, enabling an extension of the cFDR framework that supports auxiliary covariates from arbitrary continuous distributions ("Flexible cFDR"). Our method can be applied iteratively, thereby supporting multi-dimensional covariate data. Through simulations we show that Flexible cFDR increases sensitivity whilst controlling FDR after one or several iterations. We further demonstrate its practical potential through application to an asthma GWAS, leveraging various functional genomic data to find additional genetic associations for asthma, which we validate in the larger, independent, UK Biobank data resource.

A more accurate method for colocalisation analysis allowing for multiple causal variants.

In genome-wide association studies (GWAS) it is now common to search for, and find, multiple causal variants located in close proximity. It has also become standard to ask whether different traits share the same causal variants, but one of the popular methods to answer this question, coloc, makes the simplifying assumption that only a single causal variant exists for any given trait in any genomic region. Here, we examine the potential of the recently proposed Sum of Single Effects (SuSiE) regression framework, which can be used for fine-mapping genetic signals, for use with coloc. SuSiE is a novel approach that allows evidence for association at multiple causal variants to be evaluated simultaneously, whilst separating the statistical support for each variant conditional on the causal signal being considered. We show this results in more accurate coloc inference than other proposals to adapt coloc for multiple causal variants based on conditioning. We therefore recommend that coloc be used in combination with SuSiE to optimise accuracy of colocalisation analyses when multiple causal variants exist.

Detecting chromosomal interactions in Capture Hi-C data with CHiCAGO and companion tools.

Capture Hi-C is widely used to obtain high-resolution profiles of chromosomal interactions involving, at least on one end, regions of interest such as gene promoters. Signal detection in Capture Hi-C data is challenging and cannot be adequately accomplished with tools developed for other chromosome conformation capture methods, including standard Hi-C. Capture Hi-C Analysis of Genomic Organization (CHiCAGO) is a computational pipeline developed specifically for Capture Hi-C analysis. It implements a statistical model accounting for biological and technical background components, as well as bespoke normalization and multiple testing procedures for this data type. Here we provide a step-by-step guide to the CHiCAGO workflow that is aimed at users with basic experience of the command line and R. We also describe more advanced strategies for tuning the key parameters for custom experiments and provide guidance on data preprocessing and downstream analysis using companion tools. In a typical experiment, CHiCAGO takes ~2-3 h to run, although pre- and postprocessing steps may take much longer.

RápidoPGS: a rapid polygenic score calculator for summary GWAS data without a test dataset.

MOTIVATION: Polygenic scores (PGS) aim to genetically predict complex traits at an individual level. PGS are typically trained on genome-wide association summary statistics and require an independent test dataset to tune parameters. More recent methods allow parameters to be tuned on the training data, removing the need for independent test data, but approaches are computationally intensive. Based on fine-mapping principles, we present RápidoPGS, a flexible and fast method to compute PGS requiring summary-level Genome-wide association studies (GWAS) datasets only, with little computational requirements and no test data required for parameter tuning. RESULTS: We show that RápidoPGS performs slightly less well than two out of three other widely used PGS methods (LDpred2, PRScs and SBayesR) for case-control datasets, with median r2 difference: -0.0092, -0.0042 and 0.0064, respectively, but up to 17 000-fold faster with reduced computational requirements. RápidoPGS is implemented in R and can work with user-supplied summary statistics or download them from the GWAS catalog. AVAILABILITY AND IMPLEMENTATION: Our method is available with a GPL license as an R package from CRAN and GitHub. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.