Friday, March 4, 2016

Are Antibiotics Back in Favor for Abscesses?

A couple years ago, the IDSA came out with antibiotic treatment guidelines covering uncomplicated cutaneous abscesses.  The simple, straightforward treatment many of us have been advocating: incision and drainage without antibiotics.

Sadly, such days may be finished.

A few years back, a small trial found no statistically difference in clinical cure for patients randomized to trimethoprim-sulfamethoxazole or placebo – but there were concerns regarding whether the study was appropriately powered.  This, larger, multi-center, double-blind, randomized, placebo-controlled trial aims to rectify that flaw.

With the usual exclusions for patients with serious comorbid disease, these authors enrolled 1,265 to ultimately analyze 1,247.  Acute abscesses of greater than 2.0cm, but still appropriate for outpatient management, were randomized either to 7 days of TMP-SMX or identical-appearing placebo.  There were several different follow-up time frames: for initial clinical improvement, “test of cure”, and for secondary outcomes of abscess recurrence.

There’s not much debate on the outcome – with the TMP-SMX arm generating a fairly consistent ~7% absolute cure rate improvement over placebo.  In the per-protocol population, which excluded patients lost to follow-up, cure rate was 92.9% in the TMP-SMX group versus 85.7% in the placebo cohort.  Furthermore, throughout every meaningful secondary outcome – particularly new skin infection at another site or an infection occurring in a household member – TMP-SMX was favored in proportions of similar absolute magnitude.  Adverse events were similar between each group, without a preponderance of apparent harms from TMP-SMX.

An NNT of ~14 is nothing at which to scoff.  The costs of the intervention are fairly low.  We are definitely missing some of the granular detail in this first publication, and it is difficult to say whether it's generalizable to smaller abscess or how to manage abscesses with minimal surrounding cellulitis.  I look forward to these follow-up analyses to potentially improve the precision of treatment – but, in the meantime, it may be time to roll back some of our antibiotic stewardship movements in MRSA-endemic regions.

“Trimethoprim–Sulfamethoxazole versus Placebo for Uncomplicated Skin Abscess”
http://www.nejm.org/doi/full/10.1056/NEJMoa1507476

3 comments:

  1. Am I the only one thrown off a little bit by the nomenclature?

    A 2x2.5cm abscess with a 7x5cm surrounding area of erythema to me sounds like an "abscess with cellulitis", and not an "uncomplicated abscess".

    Do they mean "uncomplicated" in that, the pt's are not systemically sick with fever?

    I also had a very hard time trying to make sense of the three different reported analysis plans.

    The Supplementary Material online also reads as if there are going to be a few more studies coming out of this group about abx for skin and soft tissue infections.

    ReplyDelete
    Replies
    1. I'd expect this to be just the first of many data-dredging expeditions on this data to help better inform treatment. I'll bet erythema extent will be reported upon in the future.

      I think, as far as "complicated", they're using a pragmatic definition addressing whether deeper soft tissues are involved requiring surgical intervention and whether it can be managed as an outpatient. I.e., if an ED doc can do it and send it home it's not complicated.

      Delete
    2. They report some numbers on what these pus pockets looked like in Table 2.

      Delete

Comments on posts > 10 days old will be moderated; blame spammers.