Cath Lab Digest

David G. Armstrong, DPM, MSc, PhD: Can you comment on the Infectious Diseases Society of America (IDSA) infection classification and how it has had an impact on the current standard of care? How does this relate to international classifications of the International Working Group for the Diabetic Foot? How are these two classifications interrelated?

Benjamin Lipsky, MD: Having chaired both committees, it is a pleasure for me to be able to discuss these classification schemes. In May 2003, the guidelines from the International Working Group for the Diabetic Foot were published on a DVD and are partially accessible on the Web site www.iwgdf.org. I also authored a summary of these guidelines that was published in 2004.^1,2 In October 2004, the IDSA guidelines were published, first in Clinical Infectious Diseases, an official journal of the IDSA, and later in the Journal of the American Podiatric Medical Association (JAPMA).^3,4 These guidelines have received a good deal of press coverage and I have received much feedback from colleagues that they are useful and clinically practical.
We spent a great deal of time on the classification schemes. Since there are so many classifications for diabetic foot wounds but relatively few for infections, we tried to come up with a scheme that would be fairly easy to remember and usable.

For the International Work Group, we use the acronym PEDIS.⁵
P = perfusion
E = extent or size
D = depth or tissue loss
I = infection
S = sensation or neuropathy

Infection has the following grades:
Grade 1: no signs or symptoms of infection
Grade 2: in subcutaneous tissue only
Grade 3: extensive erythema, infection of deeper tissue
Grade 4: systemic inflammatory response indicating severe infection

These grades of infection correlate exactly with the IDSA categories (i.e., no infection, mild, moderate and severe) and were intended to do that. I think they provide a reasonably useful, easy to remember classification that facilitates easy clinical application.

Understanding The Different Classes Of Bacteria
Warren Joseph, DPM: These are two incredibly complex and thorough but easy to use documents. Both documents are still relatively new with the IDSA classification being the newer of the two.
In my perspective, the whole concept of aerobic gram positive cocci as a vital part of diabetic foot infections is the single most important “take home” message from the new classifications. For years, this has gone in circles. Back in the ‘60s and the ‘70s, people used to say that all infections were caused by Staph and Strep. Then in the late ‘70s and into the ‘80s, work by Sapico, Wheat, LeFrock and others showed that these diabetic foot infections are polymicrobial infections.⁶ However, none of these studies classified the infections. They all looked at diabetic foot infections as one big group.