Hospitals’ surveillance techniques for central-line–associated bloodstream infections may vary so much that attempts to compare the results among medical centers are likely to be inaccurate, according to a Nov. 10 report in JAMA.
Such bloodstream infection rates "are considered a key patient safety measure because such infections are frequent, lead to poor patient outcomes, are costly to the medical system, and are preventable," said Dr. Michael Y. Lin of Rush University Medical Center, Chicago, and his associates.
"Publishing infection rates on hospital report cards, which is increasingly required by regulatory agencies, is intended to facilitate interhospital comparisons that inform health care consumers and provide incentive for hospitals to prevent infections," the study authors noted. But such comparisons are [valid only] if the surveillance methods are somewhat uniform and the results of hospitals’ internal reviews can be confirmed by external measures, they remarked. In addition, very few studies have examined the issue.
Most hospitals designate an employee – usually a registered nurse, medical technologist, or microbiologist trained in infection control – as their infection preventionist, who is in charge of surveillance and reporting of central-line–associated bloodstream infections, as well as other nosocomial infections. To assure a degree of uniformity, that specialist typically uses case definitions and criteria published by the Centers for Disease Control and Prevention.
But surveillance, particularly case finding, is time consuming and depends largely on the effort this individual puts into the job, the researchers cautioned. It also entails subjective factors such as judging whether a case of bacteremia stems from a central line or from some other source, or judging whether cultures that show a common skin organism denote a true infection or contamination of the sample, Dr. Lin and his colleagues said.
"The recent development of computer algorithms for central-line–associated bloodstream infection surveillance provides an opportunity to establish an objective reference standard with which to benchmark" those techniques, they noted.
Dr. Lin and his associates retrospectively studied surveillance of central-line–associated bloodstream infections in 20 intensive care units at four Midwestern academic medical centers, comparing the results of surveillance using computer algorithms (intended to cut down on rater subjectivity) with those of traditional surveillance by an infection preventionist (JAMA 2010;304:2035-41).
The retrospective review included medical, surgical, neurosurgical, cardiac, oncologic, cardiothoracic surgical, burn, bone marrow transplant, and trauma ICUs. The researchers assessed 41 12-month periods representing 241,518 patient-days and 165,963 central-line-days.
"We hypothesized that although we would find differences in the absolute infection rates estimated by infection-preventionist surveillance as opposed to computer algorithm surveillance, we would find reasonable and uniform ecologic correlation between the two methods," the investigators said. "Instead, we found weak overall correlation between the two methods and, importantly, variable correlation when stratified by medical center."
The overall median rate of bloodstream infection, as measured by infection preventionists, was 3.3 infections/1,000 central-line days. In contrast, the median rate as measured using the computer algorithm was a significantly higher: 9.0/1,000 central-line days.
Just as important, the rate of infection as measured by infection preventionists varied significantly by hospital. "Our findings suggest that there is local variation in central-line–associated bloodstream infection surveillance performance at different medical centers, raising concern for the validity of interinstitutional rate comparisons," they noted.
In recent years, public reporting of hospital infection rates increasingly has been touted as a way to compare patient safety among different institutions, the investigators said. In the United States, about one-quarter of all states require reporting of central-line–associated bloodstream infection rates from ICUs – data that patients, advocacy groups, and regulators use to compare hospitals. "Furthermore, hospital reimbursement is increasingly dependent on reported rates," Dr. Lin and his associates said.
"Our study highlights the potential fallibility of traditional surveillance methods using partially subjective criteria," they explained, "and underscores the need for cautious interpretation of these results until more reliable measures or validation against objective measures can routinely be performed."
In particular, infection preventionists can differ in their classification of ambiguous cases. Differences also exist at the institution level, such as when hospitals use different culturing practices, different methods of medical documentation, and different degrees of institutional oversight of their surveillance programs, the researchers noted.
The Centers for Disease Control and Prevention funded the study. The authors reported no financial disclosures.