Wednesday, April 21, 2010

Tracheotomy, VAP, p-values and death

There is a new RCT just published in JAMA by a large group in Italy looking at the benefits of early (day 6-8) vs late (day 13-15) tracheotomy completed in 12 ICUs. The primary endpoint was VAP. There is also a very nice accompanying editorial. There are several interesting findings. First, patients randomized to early tracheotomy were less likely to develop VAP by day 28, 14% vs 21%, but the p-value was 0.07. Since the p value was greater than 0.05, the authors were forced to say that there was no benefit from early tracheotomy.

Interestingly the also found significantly greater vent-free days, ICU-free days, successful weaning and ICU discharges in the early tracheotomy group. There was even a trend towards higher survival in the early vs late group, HR=0.80, 95% CI 0.56-1.15. The authors and editorial do a nice job of pointing out that 31% or early and 43% of the late group didn't even receive a tracheotomy due to impending extubation or death. The editorial even makes the point that selecting an early tracheotomy is really a strategy of more trachs. The study did not assess patient comfort, which may be associated with early tracheotomy.

What is always troubling to me is that scientists, editorialists, journals and clinicians are stuck in this p-value trap. Here we have a study, a very good randomized trial, which shows likely clinically significant reductions in VAP and potentially lower mortality, but since the study was underpowered we are forced to say "no difference." I wonder if you calculated how many patients are intubated each year in the US (or Italy) and reduced VAP rates by 33%, how many VAPs would be prevented and how many deaths would be prevented? I know this study should be repeated, but will it? You have a negative JAMA study, what's the incentive? I describe this phenomenon as "Death by p-value."

1 comment:

  1. I agree completely, Eli. I read this study and editorial on the plane today, in preparation for a "Meet the Professor" session on nosocomial infections I'm leading at the ACP meeting in Toronto tomorrow and Friday....after reading this "negative study", I was struggling with how to interpret these findings in the 30 second "sound bite" I will have devoted to it during the section on VAP! I had the same feeling you did--very sad that after all the effort the authors went through to perform this excellent study, the conclusions drawn likely have more to do with the number of patients enrolled than with the "true" value of early vs. late tracheostomy....

    ReplyDelete