It’s a good news, bad news situation.
The good news is that we’ve got an effective bundle of practices that can prevent most central line associated bloodstream infections (CLABSIs). Public reporting and pay-for-performance have added to the incentive for hospitals to implement these practices, leading to a dramatic nationwide decline in CLABSI rates.
The bad news for most hospitals is that the remaining events that meet the NHSN CLABSI definition represent a motley assortment of “one-offs” that aren’t clearly preventable (see this great post from Scott Fridkin for more detail, and to share your “one-offs”). Given how low the CLABSI baseline now is, just a slight “blip” in these one-offs can push a hospital’s SIR above 1 and contribute to financial penalties (for some perspective, the post-intervention CLABSI rate in the widely cited Keystone ICU project (1.4 per 1K line days) now translates to an SIR of >1 at many hospitals).
These blips result in a tremendous amount of effort by unit leadership and infection prevention programs, as they examine each event for preventability or for common themes—often concluding that the events are either secondary or mucosal-barrier injury (MBI) attributable, but don’t meet the requisite NHSN definition (so must be reported as primary CLABSIs).
HAI definitions, like lab diagnostics, perform best when applied to individuals with moderate-to-high pretest likelihood of disease (or, populations in which the disease is prevalent). This leads to a paradox for HAI surveillance—as prevention approaches improve and HAI rates fall, the positive predictive value of surveillance definitions also declines (if one defines a “true positive” as an event that meets an intuitive clinical definition of the HAI in question—e.g. an old-fashioned primary CLABSI likely to be due to breaches in the process of line insertion and care).
Aside from the time and energy spent chasing one-offs, the continued pressure on the CLABSI metric is going to result in some counterproductive approaches to reach “zero”. After all, there are really only two ways to eliminate CLABSI as it is currently defined: (1) stop using central lines, and/or (2) stop obtaining blood cultures in patients who have central lines.