The importance of the day of the week and duration of data collection in prevalence surveys of nosocomial infections

An Implementation and Visualization of the Tree-Based Scan Statistic for Safety Event Monitoring in Longitudinal Electronic Health Data

INTRODUCTION

Longitudinal electronic healthcare data hold great potential for drug safety surveillance. The tree-based scan statistic (TBSS), as implemented by the TreeScan^® software, allows for hypothesis-free signal detection in longitudinal data by grouping safety events according to branching, hierarchical data coding systems, and then identifying signals of disproportionate recording (SDRs) among the singular events or event groups.

OBJECTIVE

The objective of this analysis was to identify and visualize SDRs with the TBSS in historical data from patients using two antifungal drugs, itraconazole or terbinafine. By examining patients who used either itraconazole or terbinafine, we provide a conceptual replication of a previous TBSS analyses by varying methodological choices and using a data source that had not been previously used with the TBSS, i.e., the Optum Clinformatics™ claims database. With this analysis, we aimed to test a parsimonious design that could be the basis of a broadly applicable method for multiple drug and safety event pairs.

METHODS

The TBSS analysis was used to examine incident events and any itraconazole or terbinafine use among US-based patients from 2002 through 2007. Event frequencies before and after the first day of drug exposure were compared over 14- and 56-day periods of observation in a Bernoulli model with a self-controlled design. Safety events were classified into a hierarchical tree structure using the Clinical Classifications Software (CCS) which mapped International Classification of Diseases, 9th Revision (ICD-9) codes to 879 diagnostic groups. Using the TBSS, the log likelihood ratio of observed versus expected events in all groups along the CCS hierarchy were compared, and groups of events that occurred at disproportionally high frequencies were identified as potential SDRs; p-values for the potential SDRs were estimated with Monte-Carlo permutation based methods. Output from TreeScan^® was visualized and plotted as a network which followed the CCS tree structure.

RESULTS

Terbinafine use (n = 223,968) was associated with SDRs for diseases of the circulatory system (14- and 56-day p = 0.001) and heart (14-day p = 0.026 and 56-day p = 0.001) as well as coronary atherosclerosis and other heart disease (14-day p = 0.003 and 56-day p = 0.004). For itraconazole use (n = 36,025), the TBSS identified SDRs for coronary atherosclerosis and other heart disease (p = 0.002) and complications of an implanted or grafted device (14-day p = 0.001 and 56-day p < 0.05). Use of both drugs was associated with SDRs for diseases of the digestive system at 14 days (p < 0.05) and this SDR had been observed among terbinafine users in a previous TBSS analysis with a different data source. The TreeScan^® visualization facilitated the identification of the atherosclerosis and other heart disease SDRs as well as highlighting the consistency of the SDR for diseases of the digestive system across drugs and data sources.

CONCLUSION

With the TBSS, we identified potential SDRs related to the circulatory system that may reflect the cardiac risk that was described in the itraconazole product label. SDRs for diseases of the digestive system among terbinafine users were also reported in a previous signal detection analysis, although other SDRs from the previous publications were not replicated. The TBSS visualizations aided in the understanding and interpretation of the TBSS output, including the comparisons to the previous publications. In this conceptual replication, differences in the results observed in our analysis and the previous analyses could be attributable to variation in modeling and design choices as well as factors that were intrinsic to the underlying data sources. The broad consistency, but far from perfect concordance, of our results with the known safety profile of these antifungals including the risks from the itraconazole product label supports the rationale for continued investigations of signal detection methods across differing data sources and populations.

Epidemiology and microbiological profile comparison between community and hospital acquired infections: A multicenter retrospective study in Lebanon

BACKGROUND

The objective of this study is to identify and characterize the species resistance of different pathogens between community acquired and hospital acquired infections pointing at patients' related independent co-morbidities and socio-demographic factors.

METHODS

It was a retrospective cohort, multicenter study from five private hospitals located in Beirut and Mount Lebanon. Two hundred fifty-eight adult patients were included.

RESULTS

110 Gram negative pathogens and 26 Gram positive pathogens were implicated in hospital acquired infections. The Gram-negative bacteria that showed a positive correlation regarding patient's type of infection were Pseudomonas aeruginosa (12%), Klebsiella pneumoniae (6.2%) and Acinetobacter baumannii (3.1%). These bacteria were more frequent in patients with hospital acquired infections (P=0.002, 0.013 and 0.017 respectively). The ratio of methicillin resistant Staphylococcus aureus, Extended Spectrum Beta Lactamase producing Escherichia coli and K. pneumoniae and multi drug P. aeruginosa showed high significance in hospital acquired infections. The logistic regression, showed a significant relationship between resistant bacteria and age (p<0.001, ORa=5.680, CI [2.344; 13.765]) and immunosuppressed state (p=0.003, ORa=3.137, CI [1.485; 6.630]) and an inverse relationship for Chronic Obstructive Pulmonary Disease (COPD) (p=0.006, ORa=0.403, CI [0.212; 0.765]).

CONCLUSION

Our results confirm that hospital acquired infections/bacteria have higher rates of resistance when compared to community acquired; these rates increase with age, immunosuppression and are inversely proportional with COPD. Therefore, physicians should be aware of patients' comorbidities to properly guide initial therapy.

Antimicrobial resistance surveillance systems: Are potential biases taken into account?

BACKGROUND

The validity of surveillance systems has rarely been a topic of investigation.

OBJECTIVE

To assess potential biases that may influence the validity of contemporary antimicrobial-resistant (AMR) pathogen surveillance systems.

METHODS

In 2008, reports of laboratory-based AMR surveillance systems were identified by searching Medline. Surveillance systems were appraised for six different types of bias. Scores were assigned as '2' (good), '1' (fair) and '0' (poor) for each bias.

RESULTS

A total of 22 surveillance systems were included. All studies used appropriate denominator data and case definitions (score of 2). Most (n=18) studies adequately protected against case ascertainment bias (score = 2), with three studies and one study scoring 1 and 0, respectively. Only four studies were deemed to be free of significant sampling bias (score = 2), with 17 studies classified as fair, and one as poor. Eight studies had explicitly removed duplicates (score = 2). Seven studies removed duplicates, but lacked adequate definitions (score = 1). Seven studies did not report duplicate removal (score = 0). Eighteen of the studies were considered to have good laboratory methodology, three had some concerns (score = 1), and one was considered to be poor (score = 0).

CONCLUSION

Contemporary AMR surveillance systems commonly have methodological limitations with respect to sampling and multiple counting and, to a lesser degree, case ascertainment and laboratory practices. The potential for bias should be considered in the interpretation of surveillance data.

Distribution of outbreak reporting in health care institutions by day of the week

BACKGROUND

The notion that outbreaks are more likely to occur on Friday is prevalent among staff in health care institutions. However, there is little evidence to support or discredit this notion. We postulated that outbreaks were no more likely to be reported on any particular day of the week.

METHODS

A total of 901 institutional outbreaks in Toronto health care facilities were tabulated according to type, outbreak setting, and day of the week reported. A χ(2) goodness-of-fit test compared daily values for 7-day per week and 5-day per week periods. Post hoc partitioning was used to pinpoint specific day(s) of the week that differed significantly.

RESULTS

Fewer outbreaks were reported on Saturdays and Sundays. Further analysis examined the distribution of outbreak reporting specifically focusing on the Monday to Friday weekday period. Among the weekdays, higher proportions of outbreaks were reported on Mondays and Fridays.

CONCLUSION

Our null hypothesis was rejected. Overall, Mondays and Fridays had the highest occurrence of outbreak reporting. We suggest that this might be due to "deadline" and "catch-up" reporting related to the "weekend effect," whereby structural differences in weekend staffing affect detection of outbreaks. Such delays warrant reexamination of surveillance processes for timely outbreak detection independent of calendar cycle.

Use of anti-infective serial prevalence studies to identify and monitor hospital-acquired infection

We developed the 'Pragmatic Proxy Protocol' (PPP) to estimate the prevalence of hospital-acquired infection (HAI) by integrating our existing pharmacy serial point prevalence studies of anti-infective prescribing practices with electronic data on microbiological and radiographic markers of infection. Our method was evaluated against the standard Hospital Infection Society/Infection Control Nurses Association Protocol (HIP). In the non-surgical patients, PPP has a sensitivity of 1.00 [confidence interval (CI): 0.70-1.00] and specificity of 0.97 (CI: 0.93-0.99). PPP suggests that for non-surgical patients, the prevalence of HAI using HIP could be underestimated by 42%. PPP takes about two-thirds of the time of HIP (75 vs 106 h) and is at least one-third cheaper. It could easily be adapted to advances in electronic reporting and, with the development of Anti-infective Care Bundles, would increase its sensitivity for the detection of HAI in surgical patients. PPP could be used to increase the frequency of routine HAI surveillance to determine the overall burden of infection and assess the efficacy of intervention strategies in a timely manner allowing rapid, direct feedback and engagement with clinicians.

Group A streptococcal infections in injection drug users in Barcelona, Spain: epidemiologic, clinical, and microbiologic analysis of 3 clusters of cases from 2000 to 2003

An unexplained resurgence of Group A streptococci (GAS) infections has been observed since the mid-1980s in the United States and Europe, particularly among intravenous drug users (IDUs). Several risk factors have been identified. Mutations in the capsule synthesis regulator genes (csrRS) have been associated with an increase in virulence. From January 1998 to December 2003, we conducted a prospective and retrospective descriptive analysis of invasive GAS soft-tissue infections in IDUs in Barcelona, Spain. Clinical features were collected, and we conducted a surveillance study to identify risk factors associated with GAS soft-tissue infections. We analyzed chromosomal DNA by low cleavage restriction enzymes and used pulsed-field gel electrophoresis (PFGE) and variable gene sequence typing (VGST) of the emm gene to disclose the epidemiologic relationship between the strains. We analyzed the influence of clonality (M-type) and mutations in csrRS genes of these strains on clinical features. We identified 44 cases, all of which were grouped in 3 clusters: fall 2000, fall 2002, and fall 2003. Cellulitis with or without abscesses (75%) and fever (90.9%) were the most common clinical manifestations. Distant septic complications were infrequent (18.2%). Although all patients had severe infections (mainly bacteremic needle abscesses), their outcome with antibiotic therapy, usually beta-lactam, was successful in all cases. However, surgery was needed in 40.9% of patients. Through the surveillance study we found that infected patients had a higher number of drug injections per day (odds ratio [OR], 18.84; 95% confidence interval [CI], 4.83-79.4; p<0.00001), shared paraphernalia for drug use more frequently (OR, 11.11; 95% CI, 3.24-39.04; p<0.0001), were in a higher proportion both currently unemployed and homeless (OR, 4.22; 95% CI, 1.5-12.15; p<0.0001), were not in a methadone maintenance program (OR, 0.03; 95% CI, 0-0.19; p<0.00001), and more often bought drugs at a specific site (OR, 33.92; 95% CI, 7.44-174.93; p<0.00001) and from a specific dealer (OR, 72; 95% CI, 8-3090; p<0.00001), compared with patients not infected. The fall 2000 cluster was polyclonal, whereas the other 2 clusters were mainly due to the same strain of GAS (emm 25.2), and were defined as epidemic outbreaks. Clinically, the cases due to the clonal strain presented abscesses and needed surgery more frequently (p<0.001 and p=0.005, respectively). On the other hand, mutations in the csrRS genes were not associated with invasive GAS soft-tissue infection. There has been an increase in the number of cases of invasive GAS soft-tissue infections in IDUs in Barcelona, which seems to be related to drug users' habits and their socioeconomic status. Clonality (emm 25.2) but not mutations in the csrRS genes was associated with more severe GAS soft-tissue infections.

Prevalence surveys of healthcare-associated infections: what do they tell us, if anything?

Prevalence surveys of healthcare-associated infections offer advantages over incidence surveys, including the relative ease of performance, a reduced requirement for resources, the ability to include increased numbers of hospitals within a shorter period of time, and the possibility of more rapid data analysis and feedback. Prevalence surveys have also been shown to be useful in monitoring the effectiveness of infection control programmes. Prevalence surveys appear to be desirable when financial support, and/or the will to carry out incidence surveys, is lacking. However, it is imperative that prevalence surveys use standardised methodology and internationally recognised definitions of infection.