Vol. 3 (2007) - Original Research

Table of Contents

Directionally Sensitive Multivariate Statistical Process Control Procedures with Application to Syndromic Surveillance
Ronald D. Fricker
Current syndromic surveillance systems run multiple simultaneous univariate procedures, each focused on detecting an outbreak in a single data stream. Multivariate procedures have the potential to better detect some types of outbreaks, but most of the existing methods are directionally invariant and are thus less relevant to the problem of syndromic surveillance. This article develops two directionally sensitive multivariate procedures and compares the performance of these procedures both with the original directionally invariant procedures and with the application of multiple univariate procedures using both simulated and real syndromic surveillance data. The performance comparison is conducted using metrics and terminology from the statistical process control (SPC) literature with the intention of helping to bridge the SPC and syndromic surveillance literatures. This article also introduces a new metric, the average overlapping run length (AORL), developed to compare the performance of various procedures on limited actual syndromic surveillance data. Among the procedures compared, in the simulations the directionally sensitive multivariate cumulative sum (MCUSUM) procedure was preferred, whereas in the real data the multiple univariate CUSUMs and the MCUSUM performed similarly. This article concludes with a brief discussion of the choice of performance metrics used herein versus the metrics more commonly used in the syndromic surveillance literature (sensitivity, specificity, and timeliness), as well as some recommendations for future research.
Using quad trees to generate grid points for applications in geographic disease surveillance
Nikolaos Yiannakoulias, Anthony Karosas, Donald P. Schopflocher, Lawrence W. Svenson, M. John Hodgson
In this study, we compare two methods of generating grid points to enable efficient geographic cluster detection when the original geographical data are prohibitively numerous. One method generates uniform grid points, and the other employs quad trees to generate non-uniform grid points. We observe differences in the results of the spatial scan approach to cluster detection for both of these grid generation schemes. In both our simulated experiment, and our analysis of real data, the grid generation schemes produce different results. Generally speaking, the quad tree scheme is more sensitive to detecting high resolution spatial clusters than the uniform scheme. The quad tree grid point scheme may be a useful alternative to the uniform (and other) grid point generation schemes when it is important to set up a surveillance system sensitive to clusters at unspecified spatial resolutions. The quad tree grid scheme may also be useful in a number of other geographic surveillance applications.
Electronic medical record Support for Public health (ESP): Automated Detection and Reporting of Statutory Notifiable Diseases to Public Health Authorities
Michael Klompas, Ross Lazarus, James Daniel, Gillian A. Haney, Francis X. Campion, Benjamin A. Kruskal, Xuanlin Hou, Alfred DeMaria, Richard Platt
Clinician initiated reporting of notifiable conditions is often delayed, incomplete, and lacking in detail. We report on the deployment of Electronic medical record Support for Public health (ESP), a system we have created to automatically screen electronic medical record (EMR) systems for evidence of reportable diseases, to securely transmit disease reports to health authorities, and to respond to queries from health departments for clinical details about laboratory detected cases. ESP consists of software that constructs and analyzes a temporary database that is regularly populated with comprehensive codified encounter data from a medical practice's EMR system. The ESP database resides within the host medical practice's firewall, configured on either a central workstation to service large multi-site, multi-physician practices or as a software module running alongside a small practice's EMR system on a personal computer. The encounter data sent to ESP includes patient demographics, diagnostic codes, laboratory test results, vital signs, and medication prescriptions. ESP regularly analyzes its database for evidence of notifiable diseases. When a case is found, the server initiates a secure Health Level 7 (HL7) message to the health department. The server is also able to respond to queries from the health department for demographic data, treatment information, and pregnancy status on cases independently reported by electronic laboratory systems. ESP is designed to be compatible with any EMR system with export capability: it facilitates translation of proprietary local codes into standardized nomenclatures, shifts the analytical burden of disease identification from the host electronic medical record system to the ESP database, and is built from open source software. The system is currently being piloted in Harvard Vanguard Medical Associates, a multi-physician practice serving 350,000 patients in eastern Massachusetts. Disease detection algorithms are proving to be robust and accurate when tested on historical data. In summary, ESP is a secure, unobtrusive, flexible, and portable method for bidirectional communication between EMR systems and health departments. It is currently being used to automate the reporting of notifiable conditions but has promise to support additional public health objectives in the future.
Invited Commentary: Automated Public Health Reporting-- A Familiar but Cantankerous Friend
George Hripcsak
Klompas et al. Respond: Automated Public Health Reporting-- Possible with a Coalition of the Willing
Michael Klompas, Ross Lazarus, James Daniel, Gillian A. Haney, Francis X. Campion, Benjamin A. Kruskal, Richard Platt
Can Chief Complaints Identify Patients with Febrile Syndromes?
Wendy W. Chapman, John N. Dowling
Background Syndromic surveillance systems often classify patients into syndromic categories based on emergency department (ED) chief complaints. There exists no standard set of syndromes for syndromic surveillance, and the available syndromic case definitions demonstrate substantial heterogeneity of findings constituting the definition. The use of fever in the definition of syndromic categories is arbitrary and unsystematic. We determined whether chief complaints accurately represent whether a patient has any of five febrile syndromes: febrile respiratory, febrile gastrointestinal, febrile rash, febrile neurological, or febrile hemorrhagic. Methods We selected 1,557 patients admitted to the ED with discharge diagnoses potentially relevant to biosurveillance. We compared physician classification of the patients' chief complaints against criterion standard classifications from physician review of ED reports for five general syndromes (e.g., rash) and five febrile syndromes (e.g., febrile rash). We calculated sensitivity and specificity for general and febrile syndromes for the 1,557 cases. Results Specificity for febrile and non-febrile syndromes was high. Sensitivity for the general syndromes ranged from 34% to 41%. Sensitivity for febrile syndromes ranged from 0% to 12%. Conclusion Whereas chief complaints had modest sensitivity in predicting general syndromes correctly, they had poor sensitivity in predicting febrile syndromes. Respiratory, gastrointestinal, rash, neurological, and hemorrhagic syndromic case definitions for surveillance systems using chief complaints as input should not include fever.

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