Utility of Spatial Point-Pattern Analysis Using Residential and Workplace Geospatial Information to Localize Potential Outbreak Sources.

Identifying the source of an outbreak facilitates its control. Spatial methods are not optimally used in outbreak investigation, due to a mix of the complexities involved (e.g., methods requiring additional parameter selection), imperfect performance, and lack of confidence in existing options. We simulated 30 mock outbreaks and compared 5 simple methods that do not require parameter selection but could select between mock cases' residential and workplace addresses to localize the source. Each category of site had a unique spatial distribution; residential and workplace address were visually and statistically clustered around the residential neighborhood and city center sites respectively, suggesting that the value of workplace addresses is tied to the location where an outbreak might originate. A modification to centrographic statistics that we propose-the center of minimum geometric distance with address selection-was able to localize the mock outbreak source to within a 500 m radius in almost all instances when using workplace in combination with residential addresses. In the sensitivity analysis, when given sufficient workplace data, the method performed well in various scenarios with only 10 cases. It was also successful when applied to past outbreaks, except for a multisite outbreak from a common food supplier.

Inter-rater reliability of J-point location and measurement of the magnitude of ST segment elevation at the J-point on ECGs of STEMI patients by emergency department doctors.

INTRODUCTION AND OBJECTIVES: Identification of the J-point and measurement of ST segment elevation at the J-point are important for the diagnosis of ST-elevation myocardial infarction (STEMI). We conducted a study to determine the inter-rater reliability (IRR) of J-point location and measurement of the magnitude of ST elevation at the J-point on ECGs of patients with STEMI by emergency department (ED) doctors. SUBJECTS AND METHODS: Each participant examined 20 STEMI ECGs during a 1-month period in 2013. The participants were required to locate the J-point by selecting the small 1 mm square within which the J-point is located and measure the magnitude of ST elevation at the J-point identified (rounded up to the nearest 0.5 mm). The intraclass correlation coefficient (ICC) was calculated to assess the IRR. RESULTS: Thirty doctors participated. The ICC assessing the degree to which all participants provided agreement in their assessment of the location of J-points across ECGs was 0.85 (95% CI 0.75 to 0.93), which is in the excellent range. The ICC for assessing the magnitude of ST elevation was 0.97 (95% CI 0.94 to 0.98), indicating excellent agreement as well. CONCLUSIONS: ED doctors show a high level of agreement when determining the location of J-points and measuring the magnitude of ST elevation at those J-points on ECGs of patients with STEMI. The findings support the measurement of ST segment elevation at the J-point in STEMI cases and should be regarded as a consistent standard to avoid confusion.