SAN FRANCISCO – In a national cohort of VA patients with MRSA pneumonia, treatment with linezolid was the only modifiable variable in predicting clinical success.
"Pneumonia is the No. 1 cause of infectious disease–related deaths in the United States yet there are limited treatment options for pneumonia caused by MRSA," Aisling R. Caffrey, Ph.D., said at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy. "Identification of independent predictors of clinical success can optimize patient care."
Aisling R. Caffrey, Ph.D
In an effort to identify independent predictors of clinical success in MRSA pneumonia, Dr. Caffrey, assistant professor of pharmacoepidemiology at the University of Rhode Island College of Pharmacy, and her associates conducted a retrospective cohort study of VA hospital admissions between January 2002 and September 2010 with diagnosis codes for MRSA and pneumonia. They used pharmacy records to identify initiation of linezolid or vancomycin during admission, with at least 3 days of therapy as dosed per protocol.
Patients who died or were discharged within 3 days of treatment initiation with either agent were excluded from the study, as were those whose treatment was initiated in a nursing home and those who were exposed to more than 2 consecutive days of antibiotic therapy with MRSA activity within 3 days prior to initiation of linezolid or vancomycin or during treatment with either agent.
Clinical success was defined as discharge from the hospital or intensive care unit by day 14 after treatment initiation, in the absence of death, therapy change, or intubation. Nonsuccess was defined as therapy change, intubation, discharge, and readmission, or death between treatment initiation and day 14. They also investigated numerous potential predictors of clinical success, including treatment with linezolid or vancomycin, demographics and admission characteristics, and comorbidities and medical history.
Dr. Caffrey reported data from 231 patients who received linezolid and 3,501 patients who received vancomycin. Their mean age was 70 years and most (98%) were male. Predictors of clinical success included treatment with linezolid (OR 1.53) and having a previous complication of an implant or graft (OR 1.55). Factors associated with nonsuccess included dialysis (OR 0.54), intravenous line (OR 0.76), having three or more inpatient procedures (OR 0.53), inpatient surgery (OR 0.48), urinary tract infection (0.82), previous coagulopathy (0.74), previous endocarditis (0.24), and previous amputation procedure (OR 0.72).
Dr. Caffrey acknowledged certain limitations of the study, including the reliance on diagnostic codes to ascertain the number of MRSA pneumonia cases. "We’re probably only capturing 20%-40% of MRSA diagnoses by using the diagnosis codes," she said at the meeting, which was sponsored by the American Society for Microbiology.
Low generalizability of the findings to other patient populations is another limitation: "The VA is the largest integrated health care system in the United States but it [consists of] mainly older white males with a lot of comorbidities," she explained.
She concluded that patients with MRSA pneumonia "are often complex, and identifying predictors of success is useful in maximizing clinical decision making."
The study was supported by the Department of Veterans Affairs and Pfizer.