Assessing Pathogen Transmission Opportunities: Variation in Nursing Home Staff-Resident Interactions.

OBJECTIVES: The Centers for Disease Control and Prevention (CDC) recommends implementing Enhanced Barrier Precautions (EBP) for all nursing home (NH) residents known to be colonized with targeted multidrug-resistant organisms (MDROs), wounds, or medical devices. Differences in health care personnel (HCP) and resident interactions between units may affect risk of acquiring and transmitting MDROs, affecting EBP implementation. We studied HCP-resident interactions across a variety of NHs to characterize MDRO transmission opportunities. DESIGN: 2 cross-sectional visits. SETTING AND PARTICIPANTS: Four CDC Epicenter sites and CDC Emerging Infection Program sites in 7 states recruited NHs with a mix of unit care types (≥30 beds or ≥2 units). HCP were observed providing resident care. METHODS: Room-based observations and HCP interviews assessed HCP-resident interactions, care type provided, and equipment use. Observations and interviews were conducted for 7-8 hours in 3-6-month intervals per unit. Chart reviews collected deidentified resident demographics and MDRO risk factors (eg, indwelling devices, pressure injuries, and antibiotic use). RESULTS: We recruited 25 NHs (49 units) with no loss to follow-up, conducted 2540 room-based observations (total duration: 405 hours), and 924 HCP interviews. HCP averaged 2.5 interactions per resident per hour (long-term care units) to 3.4 per resident per hour (ventilator care units). Nurses provided care to more residents (n = 12) than certified nursing assistants (CNAs) and respiratory therapists (RTs) (CNA: 9.8 and RT: 9) but nurses performed significantly fewer task types per interaction compared to CNAs (incidence rate ratio (IRR): 0.61, P < .05). Short-stay (IRR: 0.89) and ventilator-capable (IRR: 0.94) units had less varied care compared with long-term care units (P < .05), although HCP visited residents in these units at similar rates. CONCLUSIONS AND IMPLICATIONS: Resident-HCP interaction rates are similar across NH unit types, differing primarily in types of care provided. Current and future interventions such as EBP, care bundling, or targeted infection prevention education should consider unit-specific HCP-resident interaction patterns.

Environmental Contamination of Contact Precaution and Non-Contact Precaution Patient Rooms in Six Acute Care Facilities.

BACKGROUND: Environmental contamination is an important source of hospital multidrug-resistant organism (MDRO) transmission. Factors such as patient MDRO contact precautions (CP) status, patient proximity to surfaces, and unit type likely influence MDRO contamination and bacterial bioburden levels on patient room surfaces. Identifying factors associated with environmental contamination in patient rooms and on shared unit surfaces could help identify important environmental MDRO transmission routes. METHODS: Surfaces were sampled from MDRO CP and non-CP rooms, nursing stations, and mobile equipment in acute care, intensive care, and transplant units within 6 acute care hospitals using a convenience sampling approach blinded to cleaning events. Precaution rooms had patients with clinical or surveillance tests positive for methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, carbapenem-resistant Enterobacteriaceae or Acinetobacter within the previous 6 months, or Clostridioides difficile toxin within the past 30 days. Rooms not meeting this definition were considered non-CP rooms. Samples were cultured for the above MDROs and total bioburden. RESULTS: Overall, an estimated 13% of rooms were contaminated with at least 1 MDRO. MDROs were detected more frequently in CP rooms (32% of 209 room-sample events) than non-CP rooms (12% of 234 room-sample events). Surface bioburden did not differ significantly between CP and non-CP rooms or MDRO-positive and MDRO-negative rooms. CONCLUSIONS: CP room surfaces are contaminated more frequently than non-CP room surfaces; however, contamination of non-CP room surfaces is not uncommon and may be an important reservoir for ongoing MDRO transmission. MDRO contamination of non-CP rooms may indicate asymptomatic patient MDRO carriage, inadequate terminal cleaning, or cross-contamination of room surfaces via healthcare personnel hands.

Identification of patients at risk of Clostridioides difficile infection for enrollment in vaccine clinical trials.

BACKGROUND: Clostridioides difficile infection (CDI) is an important cause of diarrheal disease associated with increasing morbidity and mortality. Efforts to develop a preventive vaccine are ongoing. The goal of this study was to develop an algorithm to identify patients at high risk of CDI for enrollment in a vaccine efficacy trial. METHODS: We conducted a 2-stage retrospective study of patients aged ≥ 50 within the US Department of Veterans Affairs Health system between January 1, 2009 and December 31, 2013. Included patients had at least 1 visit in each of the 2 years prior to the study, with no CDI in the past year. We used multivariable logistic regression with elastic net regularization to identify predictors of CDI in months 2-12 (i.e., days 31 - 365) to allow time for antibodies to develop. Performance was measured using the positive predictive value (PPV) and the area under the curve (AUC). RESULTS: Elements of the predictive algorithm included age, baseline comorbidity score, acute renal failure, recent infections or high-risk antibiotic use, hemodialysis in the last month, race, and measures of recent healthcare utilization. The final algorithm resulted in an AUC of 0.69 and a PPV of 3.4%. CONCLUSIONS: We developed a predictive algorithm to identify a patient population with increased risk of CDI over the next 2-12 months. Our algorithm can be used prospectively with clinical and administrative data to facilitate the feasibility of conducting efficacy studies in a timely manner in an appropriate population.

Reinforcement of an infection control bundle targeting prevention practices for Clostridioides difficile in Veterans Health Administration nursing homes.

BACKGROUND: Clostridioides difficile infection (CDI) causes significant morbidity in nursing home residents. Our aim was to describe adherence to a bundled CDI prevention initiative, which had previously been deployed nationwide in Veterans Health Administration (VA) long-term care facilities (LTCFs), and to improve compliance with reinforcement. METHODS: A multicenter pre- and post-reinforcement of the VA bundle consisting of environmental management, hand hygiene, and contact precautions was conducted in 6 VA LTCFs. A campaign to reinforce VA bundle components, as well as to promote select antimicrobial stewardship recommendations and contact precautions for 30 days, was employed. Hand hygiene, antimicrobial usage, and environmental contamination, before and after bundle reinforcement, were assessed. RESULTS: All LTCFs reported following the guidelines for cleaning and contact precautions until diarrhea resolution pre-reinforcement. Environmental specimens rarely yielded C difficile pre- or post-reinforcement. Proper hand hygiene across all facilities did not change with reinforcement (pre 52.51%, post 52.18%), nor did antimicrobial use (pre 87-197 vs. post 84-245 antibiotic days per 1,000 resident-days). LTCFs found it challenging to maintain prolonged contact precautions. DISCUSSION: Variation in infection prevention and antimicrobial prescribing practices across LTCFs were identified and lessons learned. CONCLUSIONS: Introducing bundled interventions in LTCFs is challenging, given the available resources, and may be more successful with fewer components and more intensive execution with feedback.

Effectiveness of a multisite personal protective equipment (PPE)-free zone intervention in acute care.

OBJECTIVE: Determine the effectiveness of a personal protective equipment (PPE)-free zone intervention on healthcare personnel (HCP) entry hand hygiene (HH) and PPE donning compliance in rooms of patients in contact precautions. DESIGN: Quasi-experimental, multicenter intervention, before-and-after study with concurrent controls. SETTING: All patient rooms on contact precautions on 16 units (5 medical-surgical, 6 intensive care, 5 specialty care units) at 3 acute-care facilities (2 academic medical centers, 1 Veterans Affairs hospital). Observations of PPE donning and entry HH compliance by HCP were conducted during both study phases. Surveys of HCP perceptions of the PPE-free zone were distributed in both study phases. INTERVENTION: A PPE-free zone, where a low-risk area inside door thresholds of contact precautions rooms was demarcated by red tape on the floor. Inside this area, HCP were not required to wear PPE. RESULTS: We observed 3,970 room entries. HH compliance did not change between study phases among intervention units (relative risk [RR], 0.92; P = .29) and declined in control units (RR, 0.70; P = .005); however, the PPE-free zone did not significantly affect compliance (P = .07). The PPE-free zone effect on HH was significant only for rooms on enteric precautions (P = .008). PPE use was not significantly different before versus after the intervention (P = .15). HCP perceived the zone positively; 65% agreed that it facilitated communication and 66.8% agreed that it permitted checking on patients more frequently. CONCLUSIONS: HCP viewed the PPE-free zone favorably and it did not adversely affect PPE or HH compliance. Future infection prevention interventions should consider the complex sociotechnical system factors influencing behavior change.

Multi-state study of Enterobacteriaceae harboring extended-spectrum beta-lactamase and carbapenemase genes in U.S. drinking water.

Community-associated acquisition of extended-spectrum beta-lactamase- (ESBL) and carbapenemase-producing Enterobacteriaceae has significantly increased in recent years, necessitating greater inquiry into potential exposure routes, including food and water sources. In high-income countries, drinking water is often neglected as a possible source of community exposure to antibiotic-resistant organisms. We screened coliform-positive tap water samples (n = 483) from public and private water systems in six states of the United States for blaCTX-M, blaSHV, blaTEM, blaKPC, blaNDM, and blaOXA-48-type genes by multiplex PCR. Positive samples were subcultured to isolate organisms harboring ESBL or carbapenemase genes. Thirty-one samples (6.4%) were positive for blaCTX-M, ESBL-type blaSHV or blaTEM, or blaOXA-48-type carbapenemase genes, including at least one positive sample from each state. ESBL and blaOXA-48-type Enterobacteriaceae isolates included E. coli, Kluyvera, Providencia, Klebsiella, and Citrobacter species. The blaOXA-48-type genes were also found in non-fermenting Gram-negative species, including Shewanella, Pseudomonas and Acinetobacter. Multiple isolates were phenotypically non-susceptible to third-generation cephalosporin or carbapenem antibiotics. These findings suggest that tap water in high income countries could serve as an important source of community exposure to ESBL and carbapenemase genes, and that these genes may be disseminated by non-Enterobacteriaceae that are not detected as part of standard microbiological water quality testing.

In Data We Trust? Comparison of Electronic Versus Manual Abstraction of Antimicrobial Prescribing Quality Metrics for Hospitalized Veterans With Pneumonia.

BACKGROUND: Electronic health records provide the opportunity to assess system-wide quality measures. Veterans Affairs Pharmacy Benefits Management Center for Medication Safety uses medication use evaluation (MUE) through manual review of the electronic health records. OBJECTIVE: To compare an electronic MUE approach versus human/manual review for extraction of antibiotic use (choice and duration) and severity metrics. RESEARCH DESIGN: Retrospective. SUBJECTS: Hospitalizations for uncomplicated pneumonia occurring during 2013 at 30 Veterans Affairs facilities. MEASURES: We compared summary statistics, individual hospitalization-level agreement, facility-level consistency, and patterns of variation between electronic and manual MUE for initial severity, antibiotic choice, daily clinical stability, and antibiotic duration. RESULTS: Among 2004 hospitalizations, electronic and manual abstraction methods showed high individual hospitalization-level agreement for initial severity measures (agreement=86%-98%, κ=0.5-0.82), antibiotic choice (agreement=89%-100%, κ=0.70-0.94), and facility-level consistency for empiric antibiotic choice (anti-MRSA r=0.97, P<0.001; antipseudomonal r=0.95, P<0.001) and therapy duration (r=0.77, P<0.001) but lower facility-level consistency for days to clinical stability (r=0.52, P=0.006) or excessive duration of therapy (r=0.55, P=0.005). Both methods identified widespread facility-level variation in antibiotic choice, but we found additional variation in manual estimation of excessive antibiotic duration and initial illness severity. CONCLUSIONS: Electronic and manual MUE agreed well for illness severity, antibiotic choice, and duration of therapy in pneumonia at both the individual and facility levels. Manual MUE showed additional reviewer-level variation in estimation of initial illness severity and excessive antibiotic use. Electronic MUE allows for reliable, scalable tracking of national patterns of antimicrobial use, enabling the examination of system-wide interventions to improve quality.

Extended models for nosocomial infection: parameter estimation and model selection.

We consider extensions to previous models for patient level nosocomial infection in several ways, provide a specification of the likelihoods for these new models, specify new update steps required for stochastic integration, and provide programs that implement these methods to obtain parameter estimates and model choice statistics. Previous susceptible-infected models are extended to allow for a latent period between initial exposure to the pathogen and the patient becoming themselves infectious, and the possibility of decolonization. We allow for multiple facilities, such as acute care hospitals or long-term care facilities and nursing homes, and for multiple units or wards within a facility. Patient transfers between units and facilities are tracked and accounted for in the models so that direct importation of a colonized individual from one facility or unit to another might be inferred. We allow for constant transmission rates, rates that depend on the number of colonized individuals in a unit or facility, or rates that depend on the proportion of colonized individuals. Statistical analysis is done in a Bayesian framework using Markov chain Monte Carlo methods to obtain a sample of parameter values from their joint posterior distribution. Cross validation, deviance information criterion and widely applicable information criterion approaches to model choice fit very naturally into this framework and we have implemented all three. We illustrate our methods by considering model selection issues and parameter estimation for data on methicilin-resistant Staphylococcus aureus surveillance tests over 1 year at a Veterans Administration hospital comprising seven wards.

A Dynamic Transmission Model to Evaluate the Effectiveness of Infection Control Strategies.

BACKGROUND: The advancement of knowledge about control of antibiotic resistance depends on the rigorous evaluation of alternative intervention strategies. The STAR*ICU trial examined the effects of active surveillance and expanded barrier precautions on acquisition of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) in intensive care units. We report a reanalyses of the STAR*ICU trial using a Bayesian transmission modeling framework. METHODS: The data included admission and discharge times and surveillance test times and results. Markov chain Monte Carlo stochastic integration was used to estimate the transmission rate, importation, false negativity, and clearance separately for MRSA and VRE. The primary outcome was the intervention effect, which when less than (or greater than) zero, indicated a decreased (or increased) transmission rate attributable to the intervention. RESULTS: The transmission rate increased in both arms from pre- to postintervention (by 20% and 26% for MRSA and VRE). The estimated intervention effect was 0.00 (95% confidence interval [CI], -0.57 to 0.56) for MRSA and 0.05 (95% CI, -0.39 to 0.48) for VRE. Compared with MRSA, VRE had a higher transmission rate (preintervention, 0.0069 vs 0.0039; postintervention, 0.0087 vs 0.0046), higher importation probability (0.22 vs 0.17), and a lower clearance rate per colonized patient-day (0.016 vs 0.035). CONCLUSIONS: Transmission rates in the 2 treatment arms were statistically indistinguishable from the pre- to postintervention phase, consistent with the original analysis of the STAR*ICU trial. Our statistical framework was able to disentangle transmission from importation and account for imperfect testing. Epidemiological differences between VRE and MRSA were revealed.

Translation of Contextual Control Model to chronic disease management: A paradigm to guide design of cognitive support systems.

BACKGROUND: Electronic health records (EHRs) continue to be criticized for providing poor cognitive support. Defining cognitive support has lacked theoretical foundation. We developed a measurement model of cognitive support based on the Contextual Control Model (COCOM), which describes control characteristics of an "orderly" joint system and proposes 4 levels of control: scrambled, opportunistic, tactical, and strategic. METHODS: 35 clinicians (5 centers) were interviewed pre and post outpatient clinical visits and audiotaped during the visit. Behaviors pertaining to hypertension management were systematically mapped to the COCOM control characteristics of: (1) time horizon, (2) uncertainty assessment, (3) consideration of multiple goals, (4) causal model described, and (5) explicitness of plan. Each encounter was classified for overall mode of control. Visits with deviation versus no deviation from hypertension goals were compared. RESULTS: Reviewer agreement was high. Control characteristics differed significantly between deviation groups (Wilcox rank sum p<.01). K-means cluster analysis of control characteristics, stratified by deviation were distinct, with higher goal deviations associated with more control characteristics. CONCLUSION: The COCOM control characteristics appear to be areas of potential yield for improved user-experience design.

An Economic Analysis of Strategies to Control Clostridium Difficile Transmission and Infection Using an Agent-Based Simulation Model.

BACKGROUND: A number of strategies exist to reduce Clostridium difficile (C. difficile) transmission. We conducted an economic evaluation of "bundling" these strategies together. METHODS: We constructed an agent-based computer simulation of nosocomial C. difficile transmission and infection in a hospital setting. This model included the following components: interactions between patients and health care workers; room contamination via C. difficile shedding; C. difficile hand carriage and removal via hand hygiene; patient acquisition of C. difficile via contact with contaminated rooms or health care workers; and patient antimicrobial use. Six interventions were introduced alone and "bundled" together: (a) aggressive C. difficile testing; (b) empiric isolation and treatment of symptomatic patients; (c) improved adherence to hand hygiene and (d) contact precautions; (e) improved use of soap and water for hand hygiene; and (f) improved environmental cleaning. Our analysis compared these interventions using values representing 3 different scenarios: (1) base-case (BASE) values that reflect typical hospital practice, (2) intervention (INT) values that represent implementation of hospital-wide efforts to reduce C. diff transmission, and (3) optimal (OPT) values representing the highest expected results from strong adherence to the interventions. Cost parameters for each intervention were obtained from published literature. We performed our analyses assuming low, normal, and high C. difficile importation prevalence and transmissibility of C. difficile. RESULTS: INT levels of the "bundled" intervention were cost-effective at a willingness-to-pay threshold of $100,000/quality-adjusted life-year in all importation prevalence and transmissibility scenarios. OPT levels of intervention were cost-effective for normal and high importation prevalence and transmissibility scenarios. When analyzed separately, hand hygiene compliance, environmental decontamination, and empiric isolation and treatment were the interventions that had the greatest impact on both cost and effectiveness. CONCLUSIONS: A combination of available interventions to prevent CDI is likely to be cost-effective but the cost-effectiveness varies for different levels of intensity of the interventions depending on epidemiological conditions such as C. difficile importation prevalence and transmissibility.

Estimates of Social Contact in a Middle School Based on Self-Report and Wireless Sensor Data.

Estimates of contact among children, used for infectious disease transmission models and understanding social patterns, historically rely on self-report logs. Recently, wireless sensor technology has enabled objective measurement of proximal contact and comparison of data from the two methods. These are mostly small-scale studies, and knowledge gaps remain in understanding contact and mixing patterns and also in the advantages and disadvantages of data collection methods. We collected contact data from a middle school, with 7th and 8th grades, for one day using self-report contact logs and wireless sensors. The data were linked for students with unique initials, gender, and grade within the school. This paper presents the results of a comparison of two approaches to characterize school contact networks, wireless proximity sensors and self-report logs. Accounting for incomplete capture and lack of participation, we estimate that "sensor-detectable", proximal contacts longer than 20 seconds during lunch and class-time occurred at 2 fold higher frequency than "self-reportable" talk/touch contacts. Overall, 55% of estimated talk-touch contacts were also sensor-detectable whereas only 15% of estimated sensor-detectable contacts were also talk-touch. Contacts detected by sensors and also in self-report logs had longer mean duration than contacts detected only by sensors (6.3 vs 2.4 minutes). During both lunch and class-time, sensor-detectable contacts demonstrated substantially less gender and grade assortativity than talk-touch contacts. Hallway contacts, which were ascertainable only by proximity sensors, were characterized by extremely high degree and short duration. We conclude that the use of wireless sensors and self-report logs provide complementary insight on in-school mixing patterns and contact frequency.

The role of heterogeneity in contact timing and duration in network models of influenza spread in schools.

Influenza poses a significant health threat to children, and schools may play a critical role in community outbreaks. Mathematical outbreak models require assumptions about contact rates and patterns among students, but the level of temporal granularity required to produce reliable results is unclear. We collected objective contact data from students aged 5-14 at an elementary school and middle school in the state of Utah, USA, and paired those data with a novel, data-based model of influenza transmission in schools. Our simulations produced within-school transmission averages consistent with published estimates. We compared simulated outbreaks over the full resolution dynamic network with simulations on networks with averaged representations of contact timing and duration. For both schools, averaging the timing of contacts over one or two school days caused average outbreak sizes to increase by 1-8%. Averaging both contact timing and pairwise contact durations caused average outbreak sizes to increase by 10% at the middle school and 72% at the elementary school. Averaging contact durations separately across within-class and between-class contacts reduced the increase for the elementary school to 5%. Thus, the effect of ignoring details about contact timing and duration in school contact networks on outbreak size modelling can vary across different schools.

Assessing the potential adoption and usefulness of concurrent, action-oriented, electronic adverse drug event triggers designed for the outpatient setting.

BACKGROUND: Adverse drug event (ADE) detection is an important priority for patient safety research. Trigger tools have been developed to help identify ADEs. In previous work we developed seven concurrent, action-oriented, electronic trigger algorithms designed to prompt clinicians to address ADEs in outpatient care. OBJECTIVES: We assessed the potential adoption and usefulness of the seven triggers by testing the positive predictive validity and obtaining stakeholder input. METHODS: We adapted ADE triggers, "bone marrow toxin-white blood cell count (BMT-WBC)," "bone marrow toxin - platelet (BMT-platelet)," "potassium raisers," "potassium reducers," "creatinine," "warfarin," and "sedative hypnotics," with logic to suppress flagging events with evidence of clinical intervention and applied the triggers to 50,145 patients from three large health care systems. Four pharmacists assessed trigger positive predictive value (PPV) with respect to ADE detection (conservatively excluding ADEs occurring during clinically appropriate care) and clinical usefulness (i.e., whether the trigger alert could change care to prevent harm). We measured agreement between raters using the free kappa and assessed positive PPV for the trigger's detection of harm, clinical usefulness, and both. Stakeholders from the participating health care systems rated the likelihood of trigger adoption and the perceived ease of implementation. FINDINGS: Agreement between pharmacist raters was moderately high for each ADE trigger (kappa free > 0.60). Trigger PPVs for harm ranged from 0 (Creatinine, BMT-WBC) to 17 percent (potassium raisers), while PPV for care change ranged from 0 (WBC) to 60 percent (Creatinine). Fifteen stakeholders rated the triggers. Our assessment identified five of the seven triggers as good candidates for implementation: Creatinine, BMT-Platelet, Potassium Raisers, Potassium Reducers, and Warfarin. CONCLUSIONS: At least five outpatient ADE triggers performed well and merit further evaluation in outpatient clinical care. When used in real time, these triggers may promote care changes to ameliorate patient harm.

Efficient parameter estimation for models of healthcare-associated pathogen transmission in discrete and continuous time.

We describe two novel Markov chain Monte Carlo approaches to computing estimates of parameters concerned with healthcare-associated infections. The first approach frames the discrete time, patient level, hospital transmission model as a Bayesian network, and exploits this framework to improve greatly on the computational efficiency of estimation compared with existing programs. The second approach is in continuous time and shares the same computational advantages. Both methods have been implemented in programs that are available from the authors. We use these programs to show that time discretization can lead to statistical bias in the underestimation of the rate of transmission of pathogens. We show that the continuous implementation has similar running time to the discrete implementation, has better Markov chain mixing properties, and eliminates the potential statistical bias. We, therefore, recommend its use when continuous-time data are available.

Does universal active MRSA surveillance influence anti-MRSA antibiotic use? A retrospective analysis of the treatment of patients admitted with suspicion of infection at Veterans Affairs Medical Centers between 2005 and 2010.

OBJECTIVES: After the implementation of an active surveillance programme for MRSA in US Veterans Affairs (VA) Medical Centers, there was an increase in vancomycin use. We investigated whether positive MRSA admission surveillance tests were associated with MRSA-positive clinical admission cultures and whether the availability of surveillance tests influenced prescribers' ability to match initial anti-MRSA antibiotic use with anticipated MRSA results from clinical admission cultures. METHODS: Analyses were based on barcode medication administration data, microbiology data and laboratory data from 129 hospitals between January 2005 and September 2010. Hospitalized patient admissions were included if clinical cultures were obtained and antibiotics started within 2 days of admission. Mixed-effects logistic regression was used to examine associations between positive MRSA admission cultures and (i) admission MRSA surveillance test results and (ii) initial anti-MRSA therapy. RESULTS: Among 569,815 included admissions, positive MRSA surveillance tests were strong predictors of MRSA-positive admission cultures (OR 8.5; 95% CI 8.2-8.8). The negative predictive value of MRSA surveillance tests was 97.6% (95% CI 97.5%-97.6%). The diagnostic OR between initial anti-MRSA antibiotics and MRSA-positive admission cultures was 3.2 (95% CI 3.1-3.4) for patients without surveillance tests and was not significantly different for admissions with surveillance tests. CONCLUSIONS: The availability of nasal MRSA surveillance tests in VA hospitals did not seem to improve the ability of prescribers to predict the necessity of initial anti-MRSA treatment despite the high negative predictive value of MRSA surveillance tests. Prospective trials are needed to establish the safety and effectiveness of using MRSA surveillance tests to guide antibiotic therapy.

Improved hidden Markov model for nosocomial infections.

We propose a novel hidden Markov model (HMM) for parameter estimation in hospital transmission models, and show that commonly made simplifying assumptions can lead to severe model misspecification and poor parameter estimates. A standard HMM that embodies two commonly made simplifying assumptions, namely a fixed patient count and binomially distributed detections is compared with a new alternative HMM that does not require these simplifying assumptions. Using simulated data, we demonstrate how each of the simplifying assumptions used by the standard model leads to model misspecification, whereas the alternative model results in accurate parameter estimates.

A simulation-based assessment of strategies to control Clostridium difficile transmission and infection.

BACKGROUND: Clostridium difficile is one of the most common and important nosocomial pathogens, causing severe gastrointestinal disease in hospitalized patients. Although "bundled" interventions have been proposed and promoted, optimal control strategies remain unknown. METHODS: We designed an agent-based computer simulation of nosocomial C. difficile transmission and infection, which included components such as: patients and health care workers, and their interactions; room contamination via C. difficile shedding; C. difficile hand carriage and removal via hand hygiene; patient acquisition of C. difficile via contact with contaminated rooms or health care workers; and patient antimicrobial use. We then introduced six interventions, alone and "bundled" together: aggressive C. difficile testing; empiric isolation and treatment of symptomatic patients; improved adherence to hand hygiene and contact precautions; improved use of soap and water for hand hygiene; and improved environmental cleaning. All interventions were tested using values representing base-case, typical intervention, and optimal intervention scenarios. FINDINGS: In the base-case scenario, C. difficile infection rates ranged from 8-21 cases/10,000 patient-days, with a case detection fraction between 32%-50%. Implementing the "bundle" at typical intervention levels had a large impact on C. difficile acquisition and infection rates, although intensifying the intervention to optimal levels had much less additional impact. Most of the impact came from improved hand hygiene and empiric isolation and treatment of suspected C. difficile cases. CONCLUSION: A "bundled" intervention is likely to reduce nosocomial C. difficile infection rates, even under typical implementation conditions. Real-world implementation of the "bundle" should focus on those components of the intervention that are likely to produce the greatest impact on C. difficile infection rates, such as hand hygiene and empiric isolation and treatment of suspected cases.

Exploration of ICD-9-CM coding of chronic disease within the Elixhauser Comorbidity Measure in patients with chronic heart failure.

INTRODUCTION: International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes capture comorbidities that can be used to risk adjust nonrandom patient groups. We explored the accuracy of capturing comorbidities associated with one risk adjustment method, the Elixhauser Comorbidity Measure (ECM), in patients with chronic heart failure (CHF) at one Veterans Affairs (VA) medical center. We explored potential reasons for the differences found between the original codes assigned and conditions found through retrospective review. METHODS: This descriptive, retrospective study used a cohort of patients discharged with a principal diagnosis coded as CHF from one VA medical center in 2003. One admission per patient was used in the study; with multiple admissions, only the first admission was analyzed. We compared the assignment of original codes assigned to conditions found in a retrospective, manual review of the medical record conducted by an investigator with coding expertise as well as by physicians. Members of the team experienced with assigning ICD-9-CM codes and VA coding processes developed themes related to systemic reasons why chronic conditions were not coded in VA records using applied thematic techniques. RESULTS: In the 181-patient cohort, 388 comorbid conditions were identified; 305 of these were chronic conditions, originally coded at the time of discharge with an average of 1.7 comorbidities related to the ECM per patient. The review by an investigator with coding expertise revealed a total of 937 comorbidities resulting in 618 chronic comorbid conditions with an average of 3.4 per patient; physician review found 872 total comorbidities with 562 chronic conditions (average 3.1 per patient). The agreement between the original and the retrospective coding review was 88 percent. The kappa statistic for the original and the retrospective coding review was 0.375 with a 95 percent confidence interval (CI) of 0.352 to 0.398. The kappa statistic for the retrospective coding review and physician review was 0.849 (CI, 0.823-0.875). The kappa statistic for the original coding and the physician review was 0.340 (CI, 0.316-0.364). Several systemic factors were identified, including familiarity with inpatient VA and non-VA guidelines, the quality of documentation, and operational requirements to complete the coding process within short time frames and to identify the reasons for movement within a given facility. CONCLUSION: Comorbidities within the ECM representing chronic conditions were significantly underrepresented in the original code assignment. Contributing factors potentially include prioritization of codes related to acute conditions over chronic conditions; coders' professional training, educational level, and experience; and the limited number of codes allowed in initial coding software. This study highlights the need to evaluate systemic causes of underrepresentation of chronic conditions to improve the accuracy of risk adjustment used for health services research, resource allocation, and performance measurement.

The orderly and effective visit: impact of the electronic health record on modes of cognitive control.

The clinical Joint Cognitive System (JCS) includes the clinicians, electronic health record (EHR), and other infrastructure that maintain control in the system in the service of accomplishing clinical goals. The purpose of this study is to examine the relationship between levels of control using the COCOM model (scrambled, opportunistic, tactical, and strategic) and patterns of EHR use. Forty-five primary care visits were observed and audio-recorded. Each was coded for COCOM levels of control (IRR = 90%). Screen changes were recorded and time stamped (as either searching or entering). Levels of control were significantly related to preparation intensity (F (2,23) = 6.62; p=0.01), the number of screen changes involved in both searching (F (2,30) = 6.54; p=0.004), and entering information (F (2,22) = 9.26; p=0.001). Combined with the qualitative data, this pattern of EHR usage indicates that the system as designed may not provide effective cognitive support.