Jon P. Furuno

The Use and Interpretation of Quasi-Experimental Studies in Medical Informatics

Quasi-experimental study designs, often described as nonrandomized, pre-post intervention studies, are common in the medical informatics literature. Yet little has been written about the benefits and limitations of the quasi-experimental approach as applied to informatics studies. This paper outlines a relative hierarchy and nomenclature of quasi-experimental study designs that is applicable to medical informatics intervention studies. In addition, the authors performed a systematic review of two medical informatics journals, the Journal of the American Medical Informatics Association (JAMIA) and the International Journal of Medical Informatics (IJMI), to determine the number of quasi-experimental studies published and how the studies are classified on the above-mentioned relative hierarchy. They hope that future medical informatics studies will implement higher level quasi-experimental study designs that yield more convincing evidence for causal links between medical informatics interventions and outcomes.

Comparative effectiveness of nafcillin or cefazolin versus vancomycin in methicillin-susceptible Staphylococcus aureus bacteremia

BackgroundThe high prevalence of methicillin-resistant S. aureus (MRSA) has led clinicians to select antibiotics that have coverage against MRSA, usually vancomycin, for empiric therapy for suspected staphylococcal infections. Clinicians often continue vancomycin started empirically even when methicillin-susceptible S. aureus (MSSA) strains are identified by culture. However, vancomycin has been associated with poor outcomes such as nephrotoxicity, persistent bacteremia and treatment failure. The objective of this study was to compare the effectiveness of vancomycin versus the beta-lactam antibiotics nafcillin and cefazolin among patients with MSSA bacteremia. The outcome of interest for this study was 30-day in-hospital mortality.MethodsThis retrospective cohort study included all adult in-patients admitted to a tertiary-care facility between January 1, 2003 and June 30, 2007 who had a positive blood culture for MSSA and received nafcillin, cefazolin or vancomycin. Cox proportional hazard models were used to assess independent mortality hazards comparing nafcillin or cefazolin versus vancomycin. Similar methods were used to estimate the survival benefits of switching from vancomycin to nafcillin or cefazolin versus leaving patients on vancomycin. Each model included statistical adjustment using propensity scores which contained variables associated with an increased propensity to receive vancomycin.Results267 patients were included; 14% (38/267) received nafcillin or cefazolin, 51% (135/267) received both vancomycin and either nafcillin or cefazolin, and 35% (94/267) received vancomycin. Thirty (11%) died within 30 days. Those receiving nafcillin or cefazolin had 79% lower mortality hazards compared with those who received vancomycin alone (adjusted hazard ratio (HR): 0.21; 95% confidence interval (CI): 0.09, 0.47). Among the 122 patients who initially received vancomycin empirically, those who were switched to nafcillin or cefazolin (66/122) had 69% lower mortality hazards (adjusted HR: 0.31; 95% CI: 0.10, 0.95) compared to those who remained on vancomycin.ConclusionsReceipt of nafcillin or cefazolin was protective against mortality compared to vancomycin even when therapy was altered after culture results identified MSSA. Convenience of vancomycin dosing may not outweigh the potential benefits of nafcillin or cefazolin in the treatment of MSSA bacteremia.

Statistical Analysis and Application of Quasi Experiments to Antimicrobial Resistance Intervention Studies

Quasi-experimental study designs are frequently used to assess interventions that aim to limit the emergence of antimicrobial-resistant pathogens. However, previous studies using these designs have often used suboptimal statistical methods, which may result in researchers making spurious conclusions. Methods used to analyze quasi-experimental data include 2-group tests, regression analysis, and time-series analysis, and they all have specific assumptions, data requirements, strengths, and limitations. An example of a hospital-based intervention to reduce methicillin-resistant Staphylococcus aureus infection rates and reduce overall length of stay is used to explore these methods.

Bacterial contamination of health care workers' white coats

BACKGROUNDnPatient-to-patient transmission of nosocomial pathogens has been linked to transient colonization of health care workers, and studies have suggested that contamination of health care workers clothing, including white coats, may be a vector for this transmission.nnnMETHODSnWe performed a cross-sectional study involving attendees of medical and surgical grand rounds at a large teaching hospital to investigate the prevalence of contamination of white coats with important nosocomial pathogens, such as methicillin-sensitive Stapylococcus aureus, methicillin-resistant S aureus (MRSA), and vancomycin-resistant enterococci (VRE). Each participant completed a brief survey and cultured his or her white coat using a moistened culture swab on lapels, pockets, and cuffs.nnnRESULTSnAmong the 149 grand rounds attendees white coats, 34 (23%) were contaminated with S aureus, of which 6 (18%) were MRSA. None of the coats was contaminated with VRE. S aureus contamination was more prevalent in residents, those working in inpatient settings, and those who saw an inpatient that day.nnnCONCLUSIONnThis study suggests that a large proportion of health care workers white coats may be contaminated with S aureus, including MRSA. White coats may be an important vector for patient-to-patient transmission of S aureus.

Impact of a Computerized Clinical Decision Support System on Reducing Inappropriate Antimicrobial Use: A Randomized Controlled Trial

OBJECTIVEnMany hospitals utilize antimicrobial management teams (AMTs) to improve patient care. However, most function with minimal computer support. We evaluated the effectiveness and cost-effectiveness of a computerized clinical decision support system for the management of antimicrobial utilization.nnnDESIGNnA randomized controlled trial in adult inpatients between May 10 and August 3, 2004. Antimicrobial utilization was managed by an existing AMT using the system in the intervention arm and without the system in the control arm. The system was developed to alert the AMT of potentially inadequate antimicrobial therapy.nnnMEASUREMENTSnOutcomes assessed were hospital antimicrobial expenditures, mortality, length of hospitalization, and time spent managing antimicrobial utilization.nnnRESULTSnThe AMT intervened on 359 (16%) of 2,237 patients in the intervention arm and 180 (8%) of 2,270 in the control arm, while spending approximately one hour less each day on the intervention arm. Hospital antimicrobial expenditures were

Frequent Multidrug-Resistant Acinetobacter baumannii Contamination of Gloves, Gowns, and Hands of Healthcare Workers

285,812 in the intervention arm and

What infection control interventions should be undertaken to control multidrug-resistant gram-negative bacteria?

370,006 in the control arm, for a savings of

Increased Mortality with Accessory Gene Regulator (agr) Dysfunction in Staphylococcus aureus among Bacteremic Patients

84,194 (23%), or

Summer Peaks in the Incidences of Gram-Negative Bacterial Infection Among Hospitalized Patients

37.64 per patient. No significant difference was observed in mortality (3.26% vs. 2.95%, p = 0.55) or length of hospitalization (3.84 vs. 3.99 days, p = 0.38).nnnCONCLUSIONnUse of the system facilitated the management of antimicrobial utilization by allowing the AMT to intervene on more patients receiving inadequate antimicrobial therapy and to achieve substantial time and cost savings for the hospital. This is the first study that demonstrates in a patient-randomized controlled trial that computerized clinical decision support systems can improve existing antimicrobial management programs.

Prevalence of methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii in a long-term acute care facility

BACKGROUNDnMultidrug-resistant (MDR) gram-negative bacilli are important nosocomial pathogens.nnnOBJECTIVEnTo determine the incidence of transmission of MDR Acinetobacter baumannii and Pseudomonas aeruginosa from patients to healthcare workers (HCWs) during routine patient care.nnnDESIGNnProspective cohort study.nnnSETTINGnMedical and surgical intensive care units. Methods. We observed HCWs who entered the rooms of patients colonized with MDR A. baumannii or colonized with both MDR A. baumannii and MDR P. aeruginosa. We examined their hands before room entry, their disposable gloves and/or gowns upon completion of patient care, and their hands after removal of gloves and/or gowns and before hand hygiene.nnnRESULTSnSixty-five interactions occurred with patients colonized with MDR A. baumannii and 134 with patients colonized with both MDR A. baumannii and MDR P. aeruginosa. Of 199 interactions between HCWs and patients colonized with MDR A. baumannii, 77 (38.7% [95% confidence interval {CI}, 31.9%-45.5%]) resulted in HCW contamination of gloves and/or gowns, and 9 (4.5% [95% CI, 1.6%-7.4%]) resulted in contamination of HCW hands after glove removal before hand hygiene. Of 134 interactions with patients colonized with MDR P. aeruginosa, 11 (8.2% [95% CI, 3.6%-12.9%]) resulted in HCW contamination of gloves and/or gowns, and 1 resulted in HCW contamination of hands. Independent risk factors for contamination with MDR A. baumannii were manipulation of wound dressing (adjusted odds ratio [aOR], 25.9 [95% CI, 3.1-208.8]), manipulation of artificial airway (aOR, 2.1 [95% CI, 1.1-4.0]), time in room longer than 5 minutes (aOR, 4.3 [95% CI, 2.0-9.1]), being a physician or nurse practitioner (aOR, 7.4 [95% CI, 1.6-35.2]), and being a nurse (aOR, 2.3 [95% CI, 1.1-4.8]).nnnCONCLUSIONSnGowns, gloves, and unwashed hands of HCWs were frequently contaminated with MDR A. baumannii. MDR A. baumannii appears to be more easily transmitted than MDR P. aeruginosa and perhaps more easily transmitted than previously studied methicillin-resistant Staphylococcus aureus or vancomycin-resistant Enterococcus. This ease of transmission may help explain the emergence of MDR A. baumannii.