Publication bias

All readers of newspapers and viewers of television know that journalists like to choose the extraordinary. It is more important for them to get the attention of the reader than to inform. Newspapers write about murderers and rapists and pesticides that have extraordinary properties. We know this and are therefore very careful not to make important decisions based upon the messages from newspapers and commercial television programs. But we like to believe that scientific literature is without such bias. Nevertheless, bias in scientific publication is a real and serious problem to those who have to make risk assessments. We shall illustrate this problem by an example. 

Even high-rating scientific journals such as Science may have biased headings Pesticide Causes Parkinson s in Rats (November 2000, p. 1068). The article is very interesting, and the conclusion is very clear  

The problem with such headings is that a busy journalist may miss the rat in the heading as well as the conclusion. When such unintentionally biased reports add to all those articles where the intention of the author is to misinform, the public and politicians will have difficulty deciding. Rational risk assessment will be impossible. A review by Begg and Berlin (1989) describes the problem. 

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A very human kind of information storage breakdown referred to in the earlier anecdote is publication bias. This refers to the tendency of researchers to publish or otherwise make visible experimental results or conclusions that are considered a success or otherwise further the designs of the researcher but to discard results that are considered a failure (or at least to downplay... 

There are many peer-review publications reporting NoV outbreaks due to food and water. In spite of a recognized publication bias toward these outbreaks, there is a consensus that the scientific literature imder-estimates the contribution of NoV to food and waterborne disease (Efall et al., 2005 Hoffmann et al., 2007 O Brien et al., 2006). Source contamination of food and water is clearly implicated in NoV outbreaks around the world. 

O Brien, S. J., Gillespie, I. A., Sivanesan, M. A., Elson, R., Hughes, C., and Adak, G. K. (2006). Publication bias in foodborne outbreaks of infectious intestinal disease and its implications for evidence-based food policy. England and Wales 1992-2003. Epidemiol. Infect. 134, 667-674. 

PJ Easterbrook, JA Berlin, R Gopalan, DR Matthews. Publication bias in clinical research. Lancet 337 867-872, 1991. 

F Song, A Eastwood, S Gilbody, L Duley. The role of electronic journals in reducing publication bias. Med Inf Internet Med 24 223-229, 1999. 

There is a publication bias ( positive trials studies are more likely to be published). 

What information is lacking The phenomenon of publication bias means that the accumulated scientific literature selectively contains reports from studies with positive results, where the primary hypothesis has been confirmed and the so called null hypothesis has been discarded. 

Smith and Eggar (1997) in a letter to The Lancet, use funnel plots (shown in Figure 15.2) to illustrate publication bias and to link this with outcomes in several large trials conducted subsequent to the trials within those plots. 

In contrast, the lower part of Figure 15.2 shows a funnel plot for trials evaluating streptokinase and the meta-analysis, which combined these trials. The pattern of the individual trial results supports the absence of publication bias and the two large trials shown in the plot, ISIS-2 and GISS-1 show treatment effects entirely in line with the earlier meta-analysis. 

The combination of sophisticated challenge paradigms with biomarker detection provides new and technically advanced quantitative opportunities for PoC trials. However, objective and balanced evaluation of PoC and PoM paradigms sometimes may be hindered by publication bias trials with negative or inconclusive outcome tend to be published less frequently than studies with positive outcome, a fact that can mislead readers with regard to the predictive validity of certain models. 

Piantadosi (2005) defined publication bias as a tendency for studies with positive results, namely those finding significant differences, to be published in journals in preference to those with negative findings. This is a major concern in that the overall picture painted by the clinical literature on a particular topic can be skewed, or biased. 

Bowers et al. (2006) noted that publication bias can arise from various sources, including ... 

Publication bias can also influence published literature in an additional way. Two kinds of summary papers, systematic reviews and meta-analyses, bring together many published papers and provide a unifying report. These papers, and the implications of publication bias, are considered in the next section. 

Systematic Reviews, Meta-Analyses, and Publication Bias... 

The problem of publication bias can have a profound impact on the messages conveyed by systematic reviews and meta-analyses. When preparing to write these types of papers, authors typically conduct a computer search for articles that meet certain criteria. Examples of these criteria might be ... 

From a clinical practice perspective, a clinician s treatment of a patient may be influenced by the results of a meta-analysis. Therefore, if the result is influenced by the fact that the articles included in the analysis were not truly representative of all evaluations of the treatment, the result is not likely to be representative either. The issue of publication bias therefore is of critical importance in the context of evidence-based medicine. 

In summary, different SNPs and haplotypes in the G72/G30 region showed BD and/or SZ association in different studies. Strong between-study heterogeneities were observed for almost all the five SNPs that were analyzed in the meta-analysis. All these data suggest potential strong allelic heterogeneity at the G72/G30 locus. As usual, the conclusions from meta-analyses must be read with caution because of possible publication bias toward positive reports. 

The third major category of bias, Publication bias, applies to the evaluation of a putative risk factors across studies that are reported in the published literature. Positive findings are probably published more often than negative studies, and thus a meta analysis or review of the literature would be biased toward finding a greater effect than the true effect. 

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