Trigger happy?

The University of Maryland group has just published two new papers on the safety of contact precautions. One is an analysis of the data from the BUGG study (published in CID), which was a multicenter study of ICU patients, and the other is a matched prospective cohort analysis at an academic medical center (published in ICHE).

Here’s a quick summary of the two papers:
The authors’ conclusions for both papers are essentially the same: concerns about the safety of contact precautions should not limit the implementation of contact precautions. One paper showed no difference in adverse events and the other paper showed that contact precautions was actually safer than not being in contact precautions, which I think is a counterintuitive finding for many of us. 

The problem that I have with both of these papers is the use of the IHI Global Trigger Tool (GTT) to determine the rates of adverse events. I have three concerns:
  1. Are all of the events identified by the GTT causally linked to the exposure? For example, in the ICHE study, the strongest association was found for surgical events, and the association was highly counterintuitive: postoperative hemorrhage was found in 1/148 patients in contact precautions vs 12/148 patients not in contact precautions. Given what we know about contact precautions, particularly that it reduces healthcare worker visits, what could be the causal mechanism for a higher rate of post-operative hemorrhage in patients not in contact precautions? Is there a confounder at play here? There may very well be a causal mechanism but I’m hard pressed to think of one.
  2. The IHI GTT only looks for errors of commission, not errors of omission, and it seems likely that errors of omission would occur more commonly when a barrier to care is implemented (contact precautions).
  3. The IHI GTT sets a 20-minute time limit for the detection of errors when reviewing a patient chart whether the patient was hospitalized for 1 day or 100 days. In the ICHE study, the patients were matched on length of stay; however, I don’t think this resolves the problem. The GTT’s ability to detect error is time dependent. So when comparing two groups, if one group truly has a significantly higher rate of adverse events, a lower proportion of the events will be detected in the group that has more events, reducing the difference between the two groups. In effect we have surveillance bias.

    Even the IHI openly admits that this is an issue. Here’s a direct quote from the GTT manual:
The IHI Global Trigger Tool was never intended to identify all adverse events. Experienced reviewers familiar with the IHI Global Trigger Tool will identify almost all events greater than category E in a patient record that can be reviewed completely within the 20-minute time limit. Events in the E category of harm involve more judgment and at times are not as obvious, so these are less easily identified and may be missed. When the 20-minute time limit is enforced not all adverse events are expected to be identified.
In both of the papers, the 3 issues cited above are likely biasing towards the null, making contact precautions to appear to be safer than it is. So I continue to be concerned that contact precautions may result in less safe care. I think that most people in the hospital epidemiology community regard the University of Maryland researchers as some of the best methodologists in the field, and I certainly hold them in very high regard. Nonetheless, I’m curious about their love for the Global Trigger Tool, and hope that they share their views with us on this blog.


  1. Hi Mike, thanks for the thorough read and being held in high regard! Hope to not change that with my response.
    Like you I have concerns with the IHI Trigger Tool. However, what else do you use to monitor all cause adverse events? Previous studies of adverse events are less refined in either using passively reported events (missing great majority of events) or just doing a chart review (based on one's own whims).
    We chose the Trigger tool as the most thought out format for a chart review.
    In reality the "Trigger Tool" is mostly a list of items to review for potential signs of adverse events. Even in the fully electronic VA, it would be hard to look for trigger items first without reviewing standard notes. What happens, in effect, with the trigger tool is reviewing discharge summary, some other key notes, labs and medications.
    Although harm from care (errors of commission) are highlighted, the trigger tool includes pressure ulcers, falls and electrolyte disorders, so it would catch items from Stelfox or other papers. I don't think the 20 minute cutoff was much of a factor after training was complete (definitely not for severe adverse events).

    The main criticism I have of the Trigger Tool is that it is essentially still a chart review without such clear guidance on which areas of the chart to focus on. It also includes a general description of adverse events as harm due to medical care and not an underlying condition but would call a nursing home acquired pneumonia a harm but not neutropenia due to chemotherapy (so one has to come up with standardized rules across chart reviews).

    As to whether Contact Precautions have adverse effects, I am still not convinced one way or another (just like I'm not convinced they prevent infections). Most likely, if aggressively applied they can prevent transmission (with actual compliance monitoring etc.) but that is not the reality in most hospitals. Likewise, harms are more likely if they are used aggressively and really limit healthcare worker visits/patient contact. It seems clear they are a burden for healthcare workers though and I'm not sure we need high quality proof of harm to use them less frequently if we don't have similar proof of benefit.

    (I think we both know smart people who argue for or against them)



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