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Search of clinical trial registries in systematic reviews: a practice or just on paper?

Posted on 5th July 2021 by

Evidence Reviews

The following is a resource review of an interesting study assessing the impact of searching clinical trial registries in systematic reviews. The paper is: Impact of searching clinical trial registries in systematic reviews of pharmaceutical treatments: methodological systematic review and reanalysis of meta-analyses (pdf).

The title is a bit technical: what does it mean?

Systematic reviews provide the highest level of evidence. While performing a systematic review, the authors identify all relevant RCTs regardless of their publication status (RCTs here mean Randomized Controlled Trials).

The nature and direction of the results of a RCT affect the publication status, which may, in turn, lead to bias in the results of the systematic review. After looking at various initiatives, it is accepted that the search of trial registries is an essential tool while performing systematic reviews.

The authors in the paper have described if and how the clinical trial registries were searched in published systematic reviews of pharmacotherapy. They also evaluated the quantitative impact of searching registries in the meta-analysis.

It was observed that only 48% of the 223 published reviews analyzed reported the search of any trial registries. The authors’ search of clinical trial registries and subsequent re-analysis of data increases the quantitative value (range 0%-29%) of the meta-analysis, but finds no significant impact on the overall qualitative data and interpretation of the results.

Oh Okay, I’ve got a bit of this, but is this for me?

The paper is mainly for researchers and aims to improve the quantification of meta-analysis.

Honestly, at least at some point in our lives, we have taken one or the other medicines. The journey of pills from labs to our mouth is a long journey of around 1-2 decades passing through trials.

Based on such extensive trials we come to know about the properties, pros and cons of the drug. It’s on the basis of these trials that we get to know if pill A is better than pill B.

So, if the results of all the available trials are not taken into consideration while publishing systematic reviews, there can be scope for biased results.

Don’t you think this indirectly affects us as consumers as much as it’s directly affecting the clinicians who prescribe these?

Okay, this sounds interesting. How long will it take to go through the paper?

It took around 45 minutes to go through the paper. I had to re-read it around 3-4 times to appreciate it fully, making it a total of 2-3 hours.

It will make it easier to appreciate if equipped with:

  • Basic knowledge of statistics and study designs
  • Good knowledge of the English language
  • Motivation to read!


Searching clinical trial registries definitely increases the quantitative value of a meta-analysis, but has got little impact on the overall qualitative data. Rather, it can take into account the trials which didn’t furnish results as expected. Usually, only those trials/studies are published which have produced results in line with the expectations. So, in a way, searching the trial registries might help to reduce bias.

You can cite this paper if you are working on meta-analyses of published reviews.

The only thing I feel that is negative, as a student, is the difficulty in comprehending the intricacies of the study.

I give it a score of 4/5

Link to access the paper:


References and Resources:

You can also refer to the following blogs for reference:

Statistics Archives


Bias: how much difference does it really make in randomized trials?

An Introduction to Randomised Controlled Trials

An introduction to different types of study design


Anagha Nair

Hello Reader, I am a medical student- Batch 2018 at Lady Hardinge Medical College and Associated Hospitals, New Delhi. I am an aspiring medical professional with special interests in Medical Research , Emergency Medicine and Psychiatry. Feel free to contact me for your valuable feedbacks and suggestions! Happy Reading! View more posts from Anagha

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No Comments on Search of clinical trial registries in systematic reviews: a practice or just on paper?

  • Divyanshi

    Thanks to this,now I know what to expect while reading the paper!

    7th July 2021 at 1:40 pm
    Reply to Divyanshi
  • Khushboo Garg

    Very nice and well formatted article !
    Kudos !!!

    5th July 2021 at 5:51 pm
    Reply to Khushboo
  • Mehak

    The topic is very unique and interesting!
    Very nicely done

    5th July 2021 at 3:29 pm
    Reply to Mehak

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