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Potential nosocomial cases keyed in to algorithm
Noticing an increase in the number of positive cultures for Aspergillus at its hospital, a team of infection control professionals developed an algorithm to standardize definitions, determine clinical significance, and better identify or rule out nosocomial cases.
"Our [old] haphazard method of taking care of cultures for molds was putting them in a manila folder and getting to them when we could," said Cheryl Blane, RN, an ICP at Washington Hospital Center in Washington, DC. "We were having some construction at our facility, so we were concerned that we were having an increase in the number and amount of Aspergillus we saw on the transplant service."
Aspergillus species, ubiquitous fungi that occur in soil, water, and decaying vegetation, are primarily a threat to severely immune compromised patients such as those undergoing bone marrow or organ transplants. Most aspergillosis infections are traced to environmental sources, particularly dust-borne fungi dispersed during construction and renovation.1 (See Hospital Infection Control, January 2000, pp. 7-11.)
Positive cultures obtained after the patient had been in the hospital at least seven days triggered use of the algorithm. Blane and colleagues used the term "potential nosocomial acquisition" (PNA) for patients who met the aforementioned one-week admission criteria. "So if the [culture was obtained seven days after hospitalization], then you follow the whole algorithm," she explained. (See algorithm.) The term was applied to positive cultures from patients who had been in the inpatient or outpatient hospital setting within the preceding three weeks.
To determine the clinical significance of patients with PNA, ICPs reviewed the records and looked for radiological abnormalities that might suggest heightened risk for aspergillosis. Risk factors to determine possible clinical significance of a positive mold isolate include diabetes, steroid use, smoking history, transplant history, or other opportunistic infections.
After reviewing radiological findings and therapeutic response to antifungals, the ICP codes each case as allergic bronchopulmonary aspergillosis, aspergillosis, colonized with Aspergillus, colonized with other fungal species, fungus ball, sinusitis, or significance uncertain.
"The infection control practitioners do all of the first review, and we get the record if the patient is still in the hospital," she said. "We assign potential significance to that review, and anything that is potentially nosocomial is then secondarily reviewed by the hospital epidemiologist. If she concurs and refines’ significance, then we identify that as a nosocomial case."
Helpful for rule-outs
The analysis is used to enhance assessment of environmental risk, plan protective strategies, and identify clusters. "It was very helpful for rule-outs — for nonsignificant kinds of things," Blane said. "But it was also very helpful in identifying cases. Very few of the cases we would have otherwise missed, but some of the cases may not have come to our attention, or we wouldn’t have addressed them as readily or expeditiously as we did. We found out that review of data before the use of the algorithm indicated that we could have potentially had a problem. But in using this algorithm and cleaning up the data, if you will, we discovered that we did not. The nosocomial curve was not significant."
1. Carter CD, Barr BA. Infection control issues in construction and renovation. Infection Control Hosp Epidemiol 1997; 18:587-596.