Being a credible virtual witness

Tim Clark introduced me to the notion of a scientific paper acting as a virtual witness upon a scientific investigation. We, the readers, weren’t there to see the experiment being done, but the scientific article acts as a “witness statement” upon the work for us to judge that work. There’s been a deal of work over recent time about how poorly methods are described in scientific papers – method is key to being able to judge the findings in a paper and then to repeat and reproduce the work. Method is thus central to a scientific paper being a “credible virtual witness”. One of the quotes on Wikipedia’s description of credible witness is “Generally, a witness is deemed to be credible if they are recognized (or can be recognized) as a source of reliable information about someone, an event, or a phenomenon”. We need papers to be credible witnesses on the phenomena they report.


We’ve recently added to this body of work on reproducibility with a systematic review of method reporting for ‘omic experiments on a set of parasite host investigations. This work was done by Oscar Florez-Vargas, a Ph.D. student supervised by Andy Brass and me; the work was also done with collaborators in Manchester researching into parasite biology. The paper is:


Oscar Flórez-Vargas, Michael Bramhall, Harry Noyes, Sheena Cruickshank, Robert Stevens, and Andy Brass. The quality of methods reporting in parasitology experiments. PLoS ONE, 9(7):e101131, July 2014.


Oscar has worked for 10 years on the immunogenetics of Chagas disease, which is caused by one of the Trypanosoma parasites. Oscar wished to do some meta-analyses by collecting together various results from ‘omics experiments. He came with one issue of apparently contradictory results – Some papers say that the Th17 immune response, T regulatory cells and Nitric Oxide may be critical to infection and others say that they are not. Our first instinct is to go to the methods used in apparently similar experiments to see if differences in the methods could explain the apparent contradiction; the methods should tell us whether these results can be reasonably compared. Unfortunately the methods of the papers involved don’t give enough information for us to know what’s going on (details of the papers are in Oscar’s article). If we are to compare results from different experiments, we have to base that comparison on the methods by which the data were produced. In a broader context, method lets us judge the validity of the results presented and should enable the results in a paper to be reproduced by other scientists.


This need to do meta-analyses of Trypanosoma experiment data caused us to look systematically at a collection of ‘omic experiments from a series of parasite host experiments (Trypanosoma, Leishmania, Toxoplasma, Plasmodium, Trichuris and Schistosoma, as well as the non-parasitic Mycobacterium). Oscar worked with our collaborating parasitologists to develop a checklist of what essential parameters that should be reported in methods sections. This included parameters in three domains – the parasite, the host and the experimental infection. Oscar then used the appropriate PRISMA guidelines in a systematic review of 23 Trypanosoma spp. papers and 10 from each of the other organisms from the literature on these experiments (all the details are in the paper – we aimed to have our method well reported…).


We looked for effects on the level of reporting from organism and publication venue (various bibliometric features such as impact factor, the journal’s h-index and citations for the article).


Perhaps not unsurprisingly the reporting of methods was not as complete as one may wish. The mean of scores achieved by Trypanosoma articles through the checklist was 65.5% (range 32–90%). The method reporting in the other organisms was similarly poor, except in Trichuriasis experiments, which achieved the highest scores and included the only paper to score 100% in all criteria. We saw no effect of publication (some negative correlation with Google Scholar citation levels, though this is confounded by the tendency of older publications to have more citations). There has been no apparent improvement in reporting over time.


Some highlights of what we found were:

  • Species were described, but strains were not and it’s known that this can have a large effect on outcome;
  • Host’s sex has an influence on immunological response and it was sometimes not described;
  • The passage treatment of the parasite influences its infectivity and this treatment was often not reported;
  • Housing and treatment of hosts (food, temperature, etc.) effects infectivity and response to infection and these were frequently not reported.


We know method reporting tends to be poor. It is unlikely that any discipline is immune from this phenomenon. Human frailty is probably at the root – as authors, we’d like to think all the parameters we describe are taken into account in the experimental design. The fault is presumably in the reporting rather than the execution. Can we get both authors and reviewers to use checklists? The trick is, I suspect, to make such checklists help scientists do their work – not a stick, but some form of carrot. This is a similar notion that Phil Lord has used in discussing semantic publishing – the semantics have to help the author do their work, not be just another hindrance. We need checklists in a form that help scientists write their methods sections. Methods need to become a first class citizen in scientific writing, rather than a bit of a chore. Method is vital to being a credible virtual witness and we need to enable us all to be credible in our witness statements.


One Response to “Being a credible virtual witness”

  1. Reporting the Age and Sex of mice in Research Papers | Robert Stevens' Blog Says:

    […] reporting in parasitology experiments in research papers. I reported on this study in a blog “being a credible virtual witness” – the gist of this is that for a research paper to act as a credible witness for a […]

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