Antibiotic controls set loose a pseudo-outbreak
November 1, 2000 3 minutes read
Antibiotic controls set loose a pseudo-outbreak
Infection rates rise 30% after policy change
In a striking example of how seemingly subtle policy changes can send a ripple effect throughout a health care system, researchers report the unusual finding that implementing antibiotic restriction policies dramatically increased their hospital infection rates.
"After finding that our rate of infections was consistently higher — compared to a fairly stable baseline over a year and a half or more — we [responded] pretty quickly," says David Calfee, MD, a fellow in infectious diseases at the University of Virginia Hospital in Charlottesville. "Something had changed."
The situation began to unfold in May 1998, when surveillance indicated the incidence of nosocomial infections had increased by 30% — from 11 to 14.3 per 1,000 patient care days. The mean number of nosocomial infections rose from 146 to 171 per month, a 17% relative increase. At the same time, there was a 7% decrease in admissions.
"There were two things going on that made our infection rates look higher," Calfee tells Hospital Infection Control. "One was the fact that, like so many other hospitals are experiencing with managed care and everything else that is going on, we were admitting fewer patients. And those that were admitted stayed for a shorter amount of time. So the denominator we used in our calculations, which was either patient care days or admissions, was smaller. That actually accounts for about half of the increased rate."
Explaining the other half was a little trickier, as investigators looked for signs of a specific pathogen or a point-source outbreak from some kind of contaminated material. "There was really no single pathogen or even a small number of pathogens that we found greater in the outbreak period," he says. "But what we did find was, overall, about a twofold increase in the number of infections being reported in which no pathogens had been identified."
Surveillance methods had not changed, but an antibiotic control program had been launched at about the same time the problems began. The outbreak was mainly limited to the adult medical and surgical wards where the activities of the antibiotic control program were focused.
"The program tries to determine if these antibiotics are necessary," he says. "A lot of times, the recommendations are not just to stop all antibiotics but streamline the antibiotics or use a more appropriate or effective regimen than what may have been chosen. The goal is to decrease the cost of antibiotics that may not be necessary, but also, in certain cases, there may not be indications for antibiotics. We are trying to decrease the pressure for the selection of resistant organisms."
As part of the program, however, physicians were required to document an infection as the reason for prescribing antibiotics, meaning some "gray zone" cases that previously were not being reported were now being recorded to justify antibiotic administration. "It wasn’t obviously a nosocomial pneumonia or a bloodstream infection, but they had enough symptoms — fever or whatever — that the physicians were certainly concerned and treated the patients with antibiotics," he says. "Our thought is that this was going on all of the time, but before our antibiotic control program was instituted, they would not necessarily feel the need to say, I think this person has a pneumonia.’ So we don’t really think that the patients changed or the physicians changed their approach to patients. It’s just that the documentation had to change in order to continue to treat the patients the way they felt that they needed to."
ICPs should be wary
The change in the diagnostic threshold for nosocomial infections essentially resulted in a pseudo-outbreak, which may be the case in other hospitals implementing similar antibiotic control programs. "Alert other people to look out for it, because these programs are becoming much more commonly employed in a lot of places," he says, "and the very same thing could happen."
Still, there are no plans to change either the diagnostic criteria or the antibiotic policy, which is resulting in decreased costs and lowering pressure for resistance, Calfee adds. "Certainly, I don’t think we can change how we report things, but there is a greater understanding that some of them are very gray zone’ calls."
Reference
1. Calfee, DP, Dill JB, Zirk NM, et al. An outbreak of nosocomial infections associated with the institution of an antibiotic control program. Abstract 19. Infectious Disease Society of America. New Orleans; Sept 7-10, 2000.
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