There is a nice Concise Communication in the May issue of ICHE out of the University of Michigan (Go Blue). The investigators were interested in the specificity of NHSN CLABSI definitions in their Critical Care Medicine Unit (CCMU) and their SICU during the period after implementation of CLABSI bundles. They excluded from review BSIs that were determined to be central line-related BSIs (CLRBSI) since they required positive cath-tip cultures or differential time to positivity. They then had all CLABSIs, as determined by unit-designated infection preventionists using NHSN definitions, reviewed further by two non-blinded ID physicians.
To cut to the chase, since this post shouldn't be longer than the original concise communication, there were 30 non-secondary BSIs in the CCMU, 10 were CLRBSI and 20 were CLABSI. Of the 20 CLABSI, 9 (45%) were considered to have central line sources, 9 were considered contaminated blood cultures and 2 were considered transient post-op BSIs. Of the 8 non-secondary BSIs in the SICU, there were no CLRBSI and 5 (63%) were intra-abdominal sources and 1 unknown non central-line source leaving 2 confirmed CLABSI. Thus, of the original 38 IP-reported CLABSIs in the two ICUs, ID physicians confirmed 21, leaving them with an positive predictive value of 55%; close to flipping a coin.
Now, I didn't read the discussion section of the paper (who has the time!), however, since they only looked at IP determined CLABSIs they can't report sensitivity or specificity; in fact they didn't calculate the PPV, I did that. Given that so many CLABSIs appeared to be contaminated blood cultures, efforts could now be directed to preventing those, but the clinical benefit to the patient would likely be small apart from a few avoiding unnecessary antibiotic exposure. Efforts spent limiting those non-BSI CLABSIs, I suspect will be undertaken since we all have to get to zero. It's just sad that those efforts won't help our patients.