Introduction Systematic reviews provide a rigorous synthesis of the best available evidence regarding a certain question. Where high-quality evidence is lacking, systematic reviewers may choose to rely on case series studies to provide information in relation to their question. However, to date there has been limited guidance on how to incorporate case series studies within systematic reviews assessing the effectiveness of an intervention, particularly with reference to assessing the methodological quality or risk of bias of these studies. Methods An international working group was formed to review the methodological literature regarding case series as a form of evidence for inclusion in systematic reviews. The group then developed a critical appraisal tool based on the epidemiological literature relating to bias within these studies. This was then piloted, reviewed and approved by the international Scientific Committee of JBI. Results The JBI critical appraisal tool for case series studies includes 10 questions addressing the internal validity and risk of bias of case series designs, particularly confounding, selection and information bias, in addition to the importance of clear reporting. Conclusion In certain situations, case series designs may represent the best available evidence to inform clinical practice. The JBI critical appraisal tool for case series offers systematic reviewers an approved method to assess the methodological quality of these studies.

Methodological quality of case series studies: an introduction to the JBI critical appraisal tool.

Preferred reporting of case series in surgery; the PROCESS guidelines.

Distinguishing cohort studies from case series is difficult. We propose a conceptualization of cohort studies in systematic reviews of comparative studies. The main aim of this conceptualization is to clarify the distinction between cohort studies and case series. We discuss the potential impact of the proposed conceptualization on the body of evidence and workload. All studies with exposure-based sampling gather multiple exposures (with at least two different exposures or levels of exposure) and enable calculation of relative risks that should be considered cohort studies in systematic reviews, including non-randomized studies. The term “enables/can” means that a predefined analytic comparison is not a prerequisite (i.e., the absolute risks per group and/or a risk ratio are provided). Instead, all studies for which sufficient data are available for reanalysis to compare different exposures (e.g., sufficient data in the publication) are classified as cohort studies. There are possibly large numbers of studies without a comparison for the exposure of interest but that do provide the necessary data to calculate effect measures for a comparison. Consequently, more studies could be included in a systematic review. Therefore, on the one hand, the outlined approach can increase the confidence in effect estimates and the strengths of conclusions. On the other hand, the workload would increase (e.g., additional data extraction and risk of bias assessment, as well as reanalyses).

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Clarifying the distinction between case series and cohort studies in systematic reviews of comparative studies: potential impact on body of evidence and workload

We conducted a systematic review with meta-analysis and qualitative synthesis. This study aims to characterize pseudarthrosis after long-segment fusion in spinal deformity by identifying incidence rates by etiology, risk factors for its development, and common features. Pseudarthrosis can be a painful and debilitating complication of spinal fusion that may require reoperation. It is poorly characterized in the setting of spinal deformity. The MEDLINE, EMBASE, and Cochrane databases were searched for clinical research including spinal deformity patients treated with long-segment fusions reporting pseudarthrosis as a complication. Meta-analysis was performed on etiologic subsets of the studies to calculate incidence rates for pseudarthrosis. Qualitative synthesis was performed to identify characteristics of and risk factors for pseudarthrosis. The review found 162 articles reporting outcomes for 16,938 patients which met inclusion criteria. In general, the included studies were of medium to low quality according to recommended reporting standards and study design. Meta-analysis calculated an incidence of 1.4% (95% CI 0.9-1.8%) for pseudarthrosis in adolescent idiopathic scoliosis, 2.2% (95% CI 1.3-3.2%) in neuromuscular scoliosis, and 6.3% (95% CI 4.3-8.2%) in adult spinal deformity. Risk factors for pseudarthrosis include age over 55, construct length greater than 12 segments, smoking, thoracolumbar kyphosis greater than 20°, and fusion to the sacrum. Choice of graft material, pre-operative coronal alignment, post-operative analgesics, and sex have no significant impact on fusion rates. Older patients with greater deformity requiring more extensive instrumentation are at higher risk for pseudarthrosis. Overall incidence of pseudarthrosis requiring reoperation is low in adult populations and very low in adolescent populations.

Pseudarthrosis in adult and pediatric spinal deformity surgery: a systematic review of the literature and meta-analysis of incidence, characteristics, and risk factors

The COVID-19 pandemic has been characterized by an unprecedented amount of published scientific articles. The aim of this study is to assess the type of articles published during the first 3 months of the COVID-19 pandemic and to compare them with articles published during 2009 H1N1 swine influenza pandemic. Two operators independently extracted and assessed all articles on COVID-19 and on H1N1 swine influenza that had an abstract and were indexed in PubMed during the first 3 months of these pandemics. Of the 2482 articles retrieved on COVID-19, 1165 were included. Over half of them were secondary articles (590, 50.6%). Common primary articles were: human medical research (340, 59.1%), in silico studies (182, 31.7%) and in vitro studies (26, 4.5%). Of the human medical research, the vast majority were observational studies and cases series, followed by single case reports and one randomized controlled trial. Secondary articles were mainly reviews, viewpoints and editorials (373, 63.2%). Limitations were reported in 42 out of 1165 abstracts (3.6%), with 10 abstracts reporting actual methodological limitations. In a similar timeframe, there were 223 articles published on the H1N1 pandemic in 2009. During the COVID-19 pandemic there was a higher prevalence of reviews and guidance articles and a lower prevalence of in vitro and animal research studies compared with the H1N1 pandemic. In conclusions, compared to the H1N1 pandemic, the majority of early publications on COVID-19 does not provide new information, possibly diluting the original data published on this disease and consequently slowing down the development of a valid knowledge base on this disease. Also, only a negligible number of published articles reports limitations in the abstracts, hindering a rapid interpretation of their shortcomings. Researchers, peer reviewers, and editors should take action to flatten the curve of secondary articles.

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Characteristics of scientific articles on COVID-19 published during the initial 3 months of the pandemic.

Case series (CS) are well-known designs in contemporary use in neurosurgery but are sometimes used in contexts that are incompatible with their true meaning as defined by epidemiologists. This inconsistent, inappropriate and incorrect use, and mislabeling impairs the appropriate indexing and sorting of evidence. Using PubMed, we systematically identified published articles that had “case series” in the “title” in 15 top-ranked neurosurgical journals from January 2008 to December 2012. The abstracts and/or full articles were scanned to identify those with descriptions of the principal method as being “case series” and then classified as “true case series” or “non-case series” by two independent investigators with 100 % inter-rater agreement. Sixty-four articles had the label “case series” in their “titles.” Based on the definition of “case series” and our appraisal of the articles using Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines, 18 articles (28.13 %) were true case series, while 46 (71.87 %) were mislabeled. Thirty-five articles (54.69 %) mistook retrospective (descriptive) cohorts for CS. CS are descriptive with an outcome-based sampling, while “descriptive cohorts” have an exposure-based sampling of patients, followed over time to assess outcome(s). A comparison group is not a defining feature of a cohort study and distinguishes descriptive from analytic cohorts. A distinction between a case report, case series, and descriptive cohorts is absolutely necessary to enable the appropriate indexing, sorting, and application of evidence. Researchers need better training in methods and terminology, and editors and reviewers should scrutinize more carefully manuscripts claiming to be “case series” studies.

Case series and descriptive cohort studies in neurosurgery: the confusion and solution

HIV serodiscordance is a sexual partnership in which one partner is infected with HIV while the other is not. Managing emotional and sexual intimacy in HIV serodiscordant unions can be difficult due to concerns about HIV transmission and the challenge of initiating and maintaining safe sex. In situations where couples are jointly aware of their HIV status, women in serodiscordant unions may face increased risk of partner violence. We conducted an investigation to assess risk factors for HIV serodiscordance and determine if HIV serodiscordance is associated with incident sexual violence among a cohort of women attending HIV post-test club services at three AIDS Information Centers (AICs) in Uganda. Using a prospective study of 250 women, we elicited information about sexual violence using structured face-to-face interviews. Sexual violence and risk factors were assessed and compared among HIV positive women in HIV discordant unions, HIV negative women in discordant unions, and HIV negative women in negative concordant unions. Multivariable logistic regression was used to assess the association between participants' serostatus and sexual violence. HIV negative women in serodiscordant relationships (36.1±11.1 years, range: 19-65 years) were significantly older than either HIV positive women in serodiscordant relationships (32.2±9.0 years, range: 18-56 years), or HIV negative women in concordant relationships (32.3±11.0 years, range: 18-62), (p=0.033). Early age at sexual debut was associated with a 2.4-fold increased risk of experiencing sexual violence (OR 2.4, 95% CI 1.27-4.65). Based on unadjusted analysis, HIV positive women in discordant relationship were at highest risk for sexual violence compared to HIV negative women in discordant unions, and HIV negative women in negative concordant unions. HIV negative women in discordant relationships and those in concordant negative relationships showed no increased risk for sexual violence. However, couples' HIV serostatus was not significant related to incident sexual violence after controlling for potential confounding covariates. Nevertheless, the results were able to elucidate the sexual violence risk factor profile of participants based on couples' HIV serostatus. Couple counseling protocols at HIV voluntary counseling and testing centers in Uganda should identify those at risk for sexual violence and develop interventions to reduce its incidence.

Julius Ngu

Papers

Case series and descriptive cohort studies in neurosurgery: the confusion and solution

Sexual violence and associated factors among women in HIV discordant and concordant relationships in Uganda.