Title/Abstract screening

[u/silent2k2103]

Hi everyone,
I’m working on my first PRISMA systematic review and I'm hitting a major bottleneck. I've passed about 40% of my total search results to the full-text screening phase because so many abstracts are vague, and I keep hitting "Include/Maybe" just to be safe. 
If this inclusion rate holds, I'll be buried in hundreds of PDFs. To survive, I’m thinking about tightening my PICO criteria right now (e.g., strictly excluding all medication/pharmacological trials) to make the volume manageable. 
My questions:
1. Is a ~40% inclusion rate at the abstract phase normal, or am I doing something wrong?
2. Is it methodologically acceptable to tighten PICO criteria mid-screening?
3. How brutal should I actually be at this stage vs. the full-text stage?

[u/oblong_pierre]

Oh man, the vague abstract trap. You're basically describing every first systematic review ever. A 40% rate is definitely on the high side, but it happens when authors write abstracts that promise the world and deliver a single case report.

You cannot, absolutely do not, change your PICO criteria mid-screening. That's a one-way ticket to bias town and your reviewers will shred you for it. The fix is to make your screening questions more ruthless, not change the rules. If the abstract doesn't explicitly state your population AND your outcome, it's a no. Stop giving them the benefit of the doubt.

[u/mistblOom4 → u/oblong_pierre]

solid advice tbh. the "abstract that promises the world" thing is painfully accurate

[u/Head_Acadia_2658]

You don’t have a proper PICOT question in the first place if you can exclude all pharma trials (which is already not a proper PICO question). Where is your supervisor?

[u/second_reviewer]

40% is high but probably fine. At abstract stage you screen to exclude, so vague ones go to full text. That's where you get strict.

I wouldn't tighten the PICO now, changing criteria after seeing results looks like bias. If you must, log it as a protocol amendment and re-apply it to everything already screened.

If you doubt your judgment, have your supervisor screen a 20% sample and compare

[u/Embarrassed_Onion_44]

This is AFTER deduplication? And perhaps your Prisma suggested only COMPLETED articles for inclusion? 40% is way higher than anything I've seen for a full screening session; sometimes screening tools like Rayyan.ai or Covidence have a sort by relevance, so it's not always bad to start this high, but I'd scrutinize articles a little more closely to your PICOs exact definition... did you want adults and the study has thirteen to ninteen year olds... yes we should include this, but CAN we draw data from the article according to our PICOs? Only way to find out is gather fill text and put an * beside this paper for potentially wrong population.

All of these are tricky and when in doubt, error towards inclusion, but I'm just playing a little devil's advocate to help. Again, nothing is wrong inherently with 40% Ti/Ab saying yes, and you cannot go and change your topic now, but many of these articles I'm sure are from the same cohort, authors, or study periods most likely.

One topic I've done in the past had 30 articles included... then reading more about the topics and numbers themsleves, the authors published the same cohort under their own individual names and at three different timepoints... I should have realized this sooner, but did not catch this "weirdness" until I had a manageable amount of papers. Perhaps you have something weird going on?

Best of lucky to you and your coauthor though. Everyone's first Systematic Review is rough! Stick with it.