Meta-analyses including data from observational studies

Synthesis methods used to combine observational studies and randomised trials in published meta-analyses

BACKGROUND

This study examined the synthesis methods used in meta-analyses pooling data from observational studies (OSs) and randomised controlled trials (RCTs) from various medical disciplines.

METHODS

We searched Medline via PubMed to identify reports of systematic reviews of interventions, including and pooling data from RCTs and OSs published in 110 high-impact factor general and specialised journals between 2015 and 2019. Screening and data extraction were performed in duplicate. To describe the synthesis methods used in the meta-analyses, we considered the first meta-analysis presented in each article.

RESULTS

Overall, 132 reports were identified with a median number of included studies of 14 [9-26]. The median number of OSs was 6.5 [3-12] and that of RCTs was 3 [1-6]. The effect estimates recorded from OSs (i.e., adjusted or unadjusted) were not specified in 82% (n = 108) of the meta-analyses. An inverse-variance common-effect model was used in 2% (n = 3) of the meta-analyses, a random-effects model was used in 55% (n = 73), and both models were used in 40% (n = 53). A Poisson regression model was used in 1 meta-analysis, and 2 meta-analyses did not report the model they used. The mean total weight of OSs in the studied meta-analyses was 57.3% (standard deviation, ± 30.3%). Only 44 (33%) meta-analyses reported results stratified by study design. Of them, the results between OSs and RCTs had a consistent direction of effect in 70% (n = 31). Study design was explored as a potential source of heterogeneity in 79% of the meta-analyses, and confounding factors were investigated in only 10% (n = 13). Publication bias was assessed in 70% (n = 92) of the meta-analyses. Tau-square was reported in 32 meta-analyses with a median of 0.07 [0-0.30].

CONCLUSION

The inclusion of OSs in a meta-analysis on interventions could provide useful information. However, considerations of several methodological and conceptual aspects of OSs, that are required to avoid misleading findings, were often absent or insufficiently reported in our sample.

Does Professional Development Effectively Support the Implementation of Inclusive Education? A Meta-Analysis

Inclusive education is a reform aimed at educating all students in general classrooms, independent of diversity features such as special educational needs, giftedness, or migration. Its successful implementation requires teachers with professional knowledge about inclusive education, skills to address the diverse needs in the classroom, and positive beliefs toward inclusive education. Teachers are provided with professional development opportunities, but are these effective in improving their learning process and positively impacting students’ behavior? We conducted a meta-analysis to address this question. The screening of 12,050 search results revealed 342 eligible studies with more than 155,000 participants and 1123 effects from four outcome categories: teachers’ knowledge, skills, and beliefs and students’ behavior. We observed positive, though varying, effects on all four outcome categories: large effects on teachers' knowledge regarding inclusive education (g = 0.93), moderate effects on teachers’ skills (g = 0.49), small effects on teachers’ beliefs (g = 0.23), and small-to-moderate effects on student behavior (g = 0.37). We also examined factors that might explain the differences in the strength of training effects. The data suggest that long-term training with high practical relevance and active learning opportunities facilitates transfer to schools.

Salmonella in Animal Feeds: A Scoping Review

The objective of this study was to describe the volume and nature of published literature on Salmonella in animal feeds using a formal scoping review methodology. A structured search followed by eligibility screening resulted in the identification of 547 relevant studies, encompassing studies conducted in the fields in which animal feeds are grown (15 studies), the manufacturing sector (106), during transportation (11), in the retail sector (15), and on-farm (226), with the sector not described for 204 studies. The most common study purposes were to estimate the prevalence of Salmonella in animal feeds (372 studies) and to identify serovars (195). The serovars that were found in animal feeds included serovars associated with human illness, with animal illness, and with serovars identified in food (livestock and poultry) intended for human consumption. There were 120 intervention studies and 83 studies conducted to evaluate potential risk factors. Within intervention and risk factor studies, there may be sufficient depth to warrant synthesis research in the areas of heat interventions, fermentation and ensiling, organic acids, season, and geographic region. Some deficiencies were identified in the completeness of reporting of key features in the relevant studies.

Modifiable management practices to improve udder health in dairy cattle during the dry period and early lactation: A scoping review

The objective of this scoping review was to characterize all available literature on modifiable management practices used during the dry period that have been evaluated for their effects on udder health in dairy cattle during the dry period and the subsequent lactation. Five databases and two conference proceedings were searched for relevant literature. Articles published in or after 1990 were eligible for inclusion. Eligible interventions or exposures were restricted to modifiable management practices; however, antimicrobial and teat sealant products were enumerated but not further characterized, as systematic reviews have been published on this topic. Other modifiable management practices were reported in 229 articles. Nutrition (n = 79), which included ration formulation and delivery (n = 44) and vitamin and mineral additives (n = 35), was the most commonly reported practice, followed by vaccines (n = 40) and modification of dry period length (n = 27). Risk of clinical mastitis (CM) was the most commonly reported outcome (n = 151); however, reporting of outcome risk periods varied widely between articles. Cure of existing intramammary infections (IMI) over the dry period (n = 40) and prevention of new IMI over the dry period (n = 54) were most commonly reported with a risk period between calving and 30 d in milk. Future systematic reviews with meta-analyses could target management practices such as nutrition, vaccines, and dry period length to quantify their effects on improving udder health during the dry period and early lactation. However, the variation in reporting of time at risk for CM and other outcomes challenges the ability of future synthesis work to inform management decisions on the basis of efficacy to cure or prevent IMI and CM. Consensus on which core outcomes should be evaluated in mastitis research and the selection of consistent risk periods for specific outcomes in animal trials is imperative.

Veterinarian barriers to knowledge translation (KT) within the context of swine infectious disease research: an international survey of swine veterinarians

Background

Food animal veterinarians face commodity specific and urgent global challenges yet conditions preventing use of best available knowledge have been sparsely studied. The American Association of Swine Veterinarians (AASV) membership (N = 1289) was surveyed online to benchmark their information priorities and their motivations and sources for keeping current with infectious disease research, and to describe their reported time, skill, access, and process as barriers to knowledge translation (KT).

Results

Respondents (n = 80) were mostly from Canada (n = 40) and the U.S.A (n = 31) and demographics approximated the AASV’s. Colleagues are the first choice for information on difficult cases (49%, 95%CI: 38–61). Half of respondents (53%, 95%CI: 41–64) spend an hour or less per week keeping up with infectious disease research. The majority reported moderate or less than moderate efficiency (62%, 95%CI: 51–72), and moderate or greater stress (59%, 95%CI: 48–70) with their process for keeping up. Journal article methods sections are commonly not read, almost a third (32%, 95% CI: 22–43) reported either they do not evaluate statistical methods or that they had poor confidence to do so, and half (52, 95%CI: 41–63) could not explain ‘confounding bias’. Approximately half (55%, 95%CI: 41-69) with direct oversight of swine herds had full access to 2 or fewer academic journals. Approximately a third of respondents (34%, 95%CI: 24–46) selected only formats involving single research studies (either full text or summaries) as preferred reading materials for keeping current over expert summaries of the body of evidence.

Conclusion

KT barriers are considerable and a source of stress for many swine veterinarians. Sub-optimal efficiency with keeping up and low confidence to appraise aspects of research are concerns. Results are consistent with previous literature and illustrate need for improved KT infrastructure and for additional training in statistical methods and interpretation of primary research. Further evaluation is warranted of why approximately a third of veterinarians in this study, for the purpose of keeping up, preferentially choose to review individual research studies over choices that would include an expert summary of the body of evidence. Consideration of reasons for this preference will be important in the planning of KT infrastructure improvements.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s12917-020-02617-8.

Intimate partner violence and child attachment: A systematic review and meta-analysis

BACKGROUND

Intimate Partner Violence (IPV) is associated with increased risk of impairment to a child's emotional, behavioural, and psychological functioning. Further, the presence of IPV is negatively associated with a child's attachment to their primary caregivers, which is an additional risk factor for social, emotional, and psychological impairment.

OBJECTIVE

The aim of this systematic review and meta-analysis was to synthesise the evidence on the association between IPV and the attachment of infants, children, and adolescents to their primary caregiver/s.

METHOD

A systematic review was completed, in accordance with the PRISMA statement, on IPV and the parent-child attachment of infants, children, and adolescents (18 years and younger). Meta-analyses were conducted to estimate the magnitude of these associations.

RESULTS

A total of 15 studies were included. IPV was significantly associated with less secure child attachment. The pooled effect sizes (Pearson's r) for both longitudinal studies (n = 5) and cross-sectional and retrospective studies combined (n = 10) were small (r = -.22, 95 % CI [-.32, -.12], p < .001; r = -.10, 95 % CI [-.203, -.001], p = .048). Subgroup analyses identified that the effect size was larger when IPV and attachment were measured during infancy compared to childhood, and when attachment was measured via observational methods compared to self-report.

CONCLUSION

While the current literature base is limited, findings can inform further research alongside clinical assessment and intervention. It can also help guide attachment- and family-based intervention for families impacted by IPV.

Non-antibiotic approaches for disease prevention and control in beef and veal production: a scoping review

Livestock producers are encouraged to reduce the use of antibiotics belonging to classes of medical importance to humans. We conducted a scoping review on non-antibiotic interventions in the form of products or management practices that could potentially reduce the need for antibiotics in beef and veal animals living under intensive production conditions. Our objectives were to systematically describe the research on this broad topic, identify specific topics that could feasibly support systematic reviews, and identify knowledge gaps. Multiple databases were searched. Two reviewers independently screened and charted the data. From the 13,598 articles screened, 722 relevant articles were charted. The number of relevant articles increased steadily from 1990. The Western European research was dominated by veal production studies whereas the North American research was dominated by beef production studies. The interventions and outcomes measured were diverse. The four most frequent interventions included non-antibiotic feed additives, vaccinations, breed type, and feed type. The four most frequent outcomes were indices of immunity, non-specific morbidity, respiratory disease, and mortality. There were seven topic areas evaluated in clinical trials that may share enough commonality to support systemic reviews. There was a dearth of studies in which interventions were compared to antibiotic comparison groups.

Quality assessment of systematic reviews and meta-analyses that examine preventive antibiotic uses and management practices designed to prevent disease in livestock

To implement effective stewardship in food animal production, it is essential that producers and veterinarians are aware of preventive interventions to reduce illness in livestock. Systematic reviews and meta-analyses (SR/MA) provide transparent, replicable, and quality-assessed overviews. At present, it is unknown how many SR/MA evaluate preventive antibiotic use or management practices aimed at reducing disease risk in animal agriculture. Further, the quality of existing reviews is unknown. Our aim was to identify reviews investigating these topics and to provide an assessment of their quality. Thirty-eight relevant reviews were identified. Quality assessment was based on the AMSTAR 2 framework for the critical appraisal of systematic reviews. The quality of most of the reviews captured was classified as critically low (84.2%, n = 32/38), and only a small percentage of the evaluated reviews did not contain critical weaknesses (7.9%, n = 3/38). Particularly, a small number of reviews reported the development of an a priori protocol (15.8%, n = 6/38), and few reviews stated that key review steps were conducted in duplicate (study selection/screening: 26.3%, n = 10/38; data extraction: 15.8%, n = 6/38). The development of high-quality reviews summarizing evidence on approaches to antibiotic reduction is essential, and thus greater adherence to quality conduct guidelines for synthesis research is crucial.

Infectious and parasitic diseases of poultry in Ethiopia: a systematic review and meta-analysis

In Ethiopia, poultry production is an important source of domestic food and nutrition security while providing income for nearly 80% of Ethiopians. However, several infectious and parasitic diseases hamper poultry production. To date, evidence on the nationwide burden of specific diseases has not been collated to inform targeting of poultry health interventions. The objective of this systematic review is to summarize and analyze the literature on poultry diseases since 2000. A detailed systematic review protocol was designed according to Cochrane collaboration, Strengthening the Reporting of Observational Studies in Epidemiology (STROBE), and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statements. The review revealed that 14 infectious and parasitic diseases of poultry were reported in 110 published studies from 2000 to 2017, and 81.82% (90/110) of the studies covered 6 diseases: Newcastle disease (ND), infectious bursal disease (IBD), avian coccidiosis, helminth infestation, ecto-parasite infestation, and Salmonella infection. The pooled prevalence estimates of ND and IBD were 44% (95% confidence interval [CI]: 27 to 63) and 41% (95% CI: 23 to 60), respectively. Among the parasitic diseases, avian coccidiosis, helminth infestation, and ecto-parasite infestation had estimated pooled prevalences of 37% (95% CI: 30 to 44), 62% (95% CI: 45 to 78), and 50% (95% CI: 33 to 68), respectively. The pooled prevalence estimate of Salmonella infection was found to be 51% (95% CI: 32 to 70). Most of the studies were conducted in central Ethiopia, in the State of Oromia, and focused on extensive farming systems. While the number of studies was low, the overall trend of disease reporting in the literature is increasing (Y = 0.99X-3.34). In conclusion, the high-pooled prevalence estimates of diseases and the scarcity of reported data for all of Ethiopia indicate an important data gap on infectious-disease distribution in the country. While the high-pooled prevalence points towards the need for intervention to control poultry diseases, there is also a need to ensure all diseases that result in production losses and public health risks are studied appropriately in all Ethiopian production systems.

Change in drink purchases in 16 Australian recreation centres following a sugar-sweetened beverage reduction initiative: an observational study

OBJECTIVE

To assess the impact of a sugar-sweetened beverage (SSB) reduction initiative on customer purchasing patterns, including volume sales of healthy and unhealthy packaged drinks and sales value of all packaged drinks, in a major Australian aquatic and recreation provider, YMCA Victoria.

DESIGN

Prospective SETTING: 16 aquatic and recreation centres in Victoria, Australia.

INTERVENTIONS

The SSB-reduction initiative aimed to remove all SSBs (excluding sports drinks) and increase healthier drink availability over a 1-year period.

PRIMARY AND SECONDARY OUTCOME MEASURES

Itemised monthly drink sales data were collected for 16 centres, over 4 years (2 years preimplementation, 1 year implementation and 1 year postimplementation). Drinks were classified as 'green' (best choice), 'amber' (choose carefully) or 'red' (limit). Interrupted time series analysis was conducted for each centre to determine the impact on volume sales of 'red' and 'green' drinks, and overall sales value. A novel meta-analysis approach was conducted to estimate the mean changes across centres.

RESULTS

Following implementation, volume sales of 'red' drinks reduced by 46.2% across centres (95% CI: -53.2% to -39.2%), 'green' drink volume did not change (0.0%, 95% CI: -13.3% to 13.2%) and total drink sales value decreased by 24.3% (95% CI: -32.0% to -16.6%).

CONCLUSIONS

The reduction of SSBs in health-promoting settings such as recreation centres is a feasible, effective public health policy that is likely to be transferable to other high-income countries with similarly unhealthy beverage offerings. However, complementary strategies should be considered to encourage customers to switch to healthier alternatives, particularly when translating policies to organisations with less flexible income streams.

Bicarbonate use and mortality outcome among critically ill patients with metabolic acidosis: A meta analysis

BACKGROUND

The use of sodium bicarbonate in the treatment of metabolic acidosis in critically ill subjects has long been a subject of debate. Despite empiric use in the setting of severe acidemia in critically ill patients, there is little data looking into the role of sodium bicarbonate in the treatment of severe metabolic acidosis in the intensive care unit (ICU) setting.

METHODS

We conducted a comprehensive search of Pubmed and Cochrane Central Register of Controlled Trials addressing bicarbonate use in the metabolic acidosis in the intensive care unit (ICU) setting. We examined mortality as end point. Pooled odds ratios (OR) and their 95% confidence intervals (CI) were calculated for all outcomes using a random-effect model.

RESULTS

The final search yielded 202 articles of which all were screened individually. A total of 11 studies were identified but 6 studies were excluded due to irrelevance in mortality outcome and methodology. Analysis was done separately for observational studies and randomized controlled trials. The pooled OR [95% CI] for mortality with bicarbonate use in the observational studies was 1.5 [0.62-3.67] with heterogeneity of 67%, while pooled OR for mortality in the randomized trials was 0.72 [0.49-1.05] (figure 2). In combining all studies, the pooled odds ratio was 0.93 95% [0.69-1.25] but with heterogeneity of 63%. After sensitivity analysis with removing the study done by Kim et al. 2013, heterogeneity was 0% with OR 0.8 [0.59-1.10].

CONCLUSION

There is no significant difference in mortality in the use of bicarbonate among critically ill patients with high anion gap metabolic acidosis predominantly driven by lactic acidosis.

Antimicrobial-based dry cow therapy approaches for cure and prevention of intramammary infections: a protocol for a systematic review and meta-analysis

In dairy herds, application of antimicrobials at drying-off is a common mastitis control measure. This article describes a protocol for systematic review and meta-analysis to address three crucial points regarding antimicrobial usage at drying-off: (1) comparative efficacy of antimicrobials used for preventing new and eliminating existing intramammary infections (IMI); (2) comparison of selective and blanket dry cow therapy approaches in preventing new and eliminating existing IMI; and (3) assessment of the extra prevention against new IMI that can be gained from using antimicrobial-teat sealant combinations versus antimicrobials alone. Five PICO (Population, Intervention, Comparator, Outcome) questions were formulated to cover the three objectives of the review. Medline, CAB Abstracts, Web of Science, and conference proceedings will be searched along with iterative screening of references. Articles will be eligible if: (1) published after 1966; (2) written in English or French; and (3) reporting field clinical trials and observational studies, conducted on dairy cows at drying-off, with at least one antimicrobial-treated group and one IMI-related outcome. Authors will independently assess the relevance of titles and abstracts, extract data, and assess bias and the overall quality of evidence. Results will be synthesized and analyzed using pairwise and network meta-analysis. The proposed study will significantly update previously conducted reviews.

A systematic review and meta-analyses of the association between 4 mycoplasma species and lower respiratory tract disease in dogs

Background

The pathogenic role of mycoplasmas in the lower respiratory tract (LRT) of dogs is debated, because mycoplasmas can be isolated from both healthy and sick dogs.

Objectives

To critically assess available data from controlled observational studies on the role of 4 mycoplasma species in LRT disease of dogs.

Design

Systematic review and meta‐analyses.

Methods

Seven electronic databases were searched for relevant publications. Risk of bias was assessed by the Newcastle‐Ottawa Scale. Meta‐analyses, stratified by mycoplasmal species, were performed using a random effects Bayesian model with noninformative priors to estimate pooled odds ratios (ORs) and 95% confidence intervals (CIs) for the association between Mycoplasma cynos, Mycoplasma canis, Mycoplasma spumans, and Mycoplasma edwardii and LRT disease in dogs.

Results

Five studies were included from 1201 references identified. All studies dealt with M. cynos, whereas 3 dealt with the other mycoplasma species. A significant association was found between M. cynos and LRT disease (Bayesian OR, 3.60; CI, 1.31‐10.29). Conversely, M. canis, M. spumans, and M. edwardii were not significantly associated with LRT signs (Bayesian OR, 1.06; CI, 0.10‐14.63; Bayesian OR, 3.40; CI, 0.16‐54.27; and Bayesian OR, 1.04; CI, 0.05‐23.54, respectively).

Conclusions and Clinical Importance

Results support a pathogenic role of M. cynos and a commensal role of M. canis and M. edwardii in LRT in dogs. Although the association was not significant based on the CI, the point estimate of the Bayesian OR was relatively high for M. spumans, making its role less clear. Mycoplasma cynos‐specific polymerase chain reaction should be considered on samples from dogs with LRT.

Association between cognitive reserve and cognitive performance in people with HIV: a systematic review and meta-analysis

Cognitive reserve is a potential explanation for the disparity between brain pathology and its clinical manifestations. The main objective of this study was to estimate, based on published studies, the strength of the association between cognitive reserve and cognitive performance in individuals with HIV. A systematic literature search using Ovid MEDLINE, PsychINFO, and EMBASE was performed to identify studies published between 1990 and 2016 that quantified the association between cognitive reserve and cognitive performance in HIV. A random-effects meta-analysis was used to compute a summary estimate (Cohen's d) with 95% confidence intervals (CI) and 95% prediction intervals (PI). The risk of bias and quality of reporting in the studies were indicated by the Appraisal tool for Cross-Sectional Studies (AXIS). Ten observational studies were deemed eligible. The pooled effect size was 0.9 (95% CI: 0.7-1.0; 95% PI: 0.4-1.4) with marked heterogeneity studies [Cochran's Q (df = 9) = 28.0, p = .0009; I² statistic = 67.4%]. Risk-of-bias appraisal showed that non-response bias was never addressed and the items associated with selection bias were only partially met. The association between cognitive reserve and cognitive performance suggests that building reserve through non-pharmacological interventions could be a potentially effective way of combating cognitive impairment in people with HIV.

Methods to systematically review and meta-analyse observational studies: a systematic scoping review of recommendations

Background

Systematic reviews and meta-analyses of observational studies are frequently performed, but no widely accepted guidance is available at present. We performed a systematic scoping review of published methodological recommendations on how to systematically review and meta-analyse observational studies.

Methods

We searched online databases and websites and contacted experts in the field to locate potentially eligible articles. We included articles that provided any type of recommendation on how to conduct systematic reviews and meta-analyses of observational studies. We extracted and summarised recommendations on pre-defined key items: protocol development, research question, search strategy, study eligibility, data extraction, dealing with different study designs, risk of bias assessment, publication bias, heterogeneity, statistical analysis. We summarised recommendations by key item, identifying areas of agreement and disagreement as well as areas where recommendations were missing or scarce.

Results

The searches identified 2461 articles of which 93 were eligible. Many recommendations for reviews and meta-analyses of observational studies were transferred from guidance developed for reviews and meta-analyses of RCTs. Although there was substantial agreement in some methodological areas there was also considerable disagreement on how evidence synthesis of observational studies should be conducted. Conflicting recommendations were seen on topics such as the inclusion of different study designs in systematic reviews and meta-analyses, the use of quality scales to assess the risk of bias, and the choice of model (e.g. fixed vs. random effects) for meta-analysis.

Conclusion

There is a need for sound methodological guidance on how to conduct systematic reviews and meta-analyses of observational studies, which critically considers areas in which there are conflicting recommendations.

Electronic supplementary material

The online version of this article (10.1186/s12874-018-0495-9) contains supplementary material, which is available to authorized users.

A systematic review and meta-analysis of the association between Mycoplasma spp and upper and lower respiratory tract disease in cats

OBJECTIVE To critically assess available data from controlled observational studies on the pathogenic role of Mycoplasma spp in the upper respiratory tract (URT) and lower respiratory tract (LRT) of cats. DESIGN Systematic review and meta-analysis. SAMPLE 12 studies. PROCEDURES Seven electronic databases were searched for relevant publications. Risk of bias was assessed via the Newcastle-Ottawa Scale. Meta-analyses, stratified by URT versus LRT disease, were performed to estimate pooled ORs and 95% confidence intervals (CIs) for the association between Mycoplasma isolation and URT or LRT disease. Subanalyses by diagnostic method, sampling site, and environment (shelter vs nonshelter) were planned for studies on URT disease. RESULTS A significant association was found between isolation of mycoplasmal organisms and URT disease (pooled OR, 1.65; 95% CI, 1.14 to 2.40) but not LRT disease (pooled OR, 1.56; 95% CI, 0.51 to 4.76). The association with URT disease was only significant when conjunctival or pharyngeal samples from nonshelter cats were analyzed with a Mycoplasma felis-specific PCR assay. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that M felis may be a primary pathogen in cats with URT disease, warranting treatment in infected cats. The environment was important to consider when interpreting a mycoplasma-positive sample because of aclinical carriage, especially in shelter cats. Further investigations are needed to determine the role, if any, of mycoplasmal organisms in LRT disease of cats.

An investigative framework to facilitate epidemiological thinking during herd problem-solving

Veterinary clinicians and students commonly use diagnostic approaches appropriate for individual cases when conducting herd problem-solving. However, these approaches can be problematic, in part because they make limited use of epidemiological principles and methods, which has clear application during the investigation of herd problems. In this paper, we provide an overview of diagnostic approaches that are used when investigating individual animal cases, and the challenges faced when these approaches are directly translated from the individual to the herd. Further, we propose an investigative framework to facilitate epidemiological thinking during herd problem-solving.

A number of different approaches are used when making a diagnosis on an individual animal, including pattern recognition, hypothetico-deductive reasoning, and the key abnormality method. Methods commonly applied to individuals are often adapted for herd problem-solving: ‘comparison with best practice’ being a herd-level adaptation of pattern recognition, and ‘differential diagnoses’ a herd-level adaptation of hypothetico-deductive reasoning. These approaches can be effective, however, challenges can arise. Herds are complex; a collection of individual cows, but also additional layers relating to environment, management, feeding etc. It is unrealistic to expect seamless translation of diagnostic approaches from the individual to the herd. Comparison with best practice is time-consuming and prioritisation of actions can be problematic, whereas differential diagnoses can lead to ‘pathogen hunting’, particularly in complex cases.

Epidemiology is the science of understanding disease in populations. The focus is on the population, underpinned by principles and utilising methods that seek to allow us to generate solid conclusions from apparently uncontrolled situations. In this paper, we argue for the inclusion of epidemiological principles and methods as an additional tool for herd problem-solving, and outline an investigative framework, with examples, to effectively incorporate these principles and methods with other diagnostic approaches during herd problem-solving. Relevant measures of performance are identified, and measures of case frequencies are calculated and compared across time, in space and among animal groupings, to identify patterns, clues and plausible hypotheses, consistent with potential biological processes. With this knowledge, the subsequent investigation (relevant on-farm activities, diagnostic testing and other examinations) can be focused, and actions prioritised (specifically, those actions that are likely to make the greatest difference in addressing the problem if enacted).

In our experience, this investigative framework is an effective teaching tool, facilitating epidemiological thinking among students during herd problem-solving. It is a generic and robust process, suited to many herd-based problems.

An introduction to systematic reviews in animal health, animal welfare, and food safety

In this paper, we provide an introduction to systematic reviews and discuss the process for conducting systematic reviews in animal health, animal welfare, and food safety. The research synthesis need that can be addressed by a systematic review is discussed. The use of systematic reviews to address questions about intervention effects, etiology, diagnostic tests evaluation and disease burden are discussed. The steps included in a systematic review are described.

The methodological quality assessment tools for preclinical and clinical studies, systematic review and meta-analysis, and clinical practice guideline: a systematic review

OBJECTIVE

To systematically review the methodological assessment tools for pre-clinical and clinical studies, systematic review and meta-analysis, and clinical practice guideline.

METHODS

We searched PubMed, the Cochrane Handbook for Systematic Reviews of Interventions, Joanna Briggs Institute (JBI) Reviewers Manual, Centre for Reviews and Dissemination, Critical Appraisal Skills Programme (CASP), Scottish Intercollegiate Guidelines Network (SIGN), and the National Institute for Clinical Excellence (NICE) up to May 20th, 2014. Two authors selected studies and extracted data; quantitative analysis was performed to summarize the characteristics of included tools.

RESULTS

We included a total of 21 assessment tools for analysis. A number of tools were developed by academic organizations, and some were developed by only a small group of researchers. The JBI developed the highest number of methodological assessment tools, with CASP coming second. Tools for assessing the methodological quality of randomized controlled studies were most abundant. The Cochrane Collaboration's tool for assessing risk of bias is the best available tool for assessing RCTs. For cohort and case-control studies, we recommend the use of the Newcastle-Ottawa Scale. The Methodological Index for Non-Randomized Studies (MINORS) is an excellent tool for assessing non-randomized interventional studies, and the Agency for Healthcare Research and Quality (ARHQ) methodology checklist is applicable for cross-sectional studies. For diagnostic accuracy test studies, the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool is recommended; the SYstematic Review Centre for Laboratory animal Experimentation (SYRCLE) risk of bias tool is available for assessing animal studies; Assessment of Multiple Systematic Reviews (AMSTAR) is a measurement tool for systematic reviews/meta-analyses; an 18-item tool has been developed for appraising case series studies, and the Appraisal of Guidelines, Research and Evaluation (AGREE)-II instrument is widely used to evaluate clinical practice guidelines.

CONCLUSIONS

We have successfully identified a variety of methodological assessment tools for different types of study design. However, further efforts in the development of critical appraisal tools are warranted since there is currently a lack of such tools for other fields, e.g. genetic studies, and some existing tools (nested case-control studies and case reports, for example) are in need of updating to be in line with current research practice and rigor. In addition, it is very important that all critical appraisal tools remain subjective and performance bias is effectively avoided.