Modeling emergency department visit patterns for infectious disease complaints: results and application to disease surveillance.

BACKGROUND: Concern over bio-terrorism has led to recognition that traditional public health surveillance for specific conditions is unlikely to provide timely indication of some disease outbreaks, either naturally occurring or induced by a bioweapon. In non-traditional surveillance, the use of health care resources are monitored in "near real" time for the first signs of an outbreak, such as increases in emergency department (ED) visits for respiratory, gastrointestinal or neurological chief complaints (CC). METHODS: We collected ED CCs from 2/1/94 - 5/31/02 as a training set. A first-order model was developed for each of seven CC categories by accounting for long-term, day-of-week, and seasonal effects. We assessed predictive performance on subsequent data from 6/1/02 - 5/31/03, compared CC counts to predictions and confidence limits, and identified anomalies (simulated and real). RESULTS: Each CC category exhibited significant day-of-week differences. For most categories, counts peaked on Monday. There were seasonal cycles in both respiratory and undifferentiated infection complaints and the season-to-season variability in peak date was summarized using a hierarchical model. For example, the average peak date for respiratory complaints was January 22, with a season-to-season standard deviation of 12 days. This season-to-season variation makes it challenging to predict respiratory CCs so we focused our effort and discussion on prediction performance for this difficult category. Total ED visits increased over the study period by 4%, but respiratory complaints decreased by roughly 20%, illustrating that long-term averages in the data set need not reflect future behavior in data subsets. CONCLUSION: We found that ED CCs provided timely indicators for outbreaks. Our approach led to successful identification of a respiratory outbreak one-to-two weeks in advance of reports from the state-wide sentinel flu surveillance and of a reported increase in positive laboratory test results.

Results from the fielding of the Bio-surveillance Analysis, Feedback, Evaluation and Response (B-SAFER) system in Albuquerque, New Mexico.

Public health authorities need a surveillance system that is sensitive enough to detect a disease outbreak early to enable a proper response. In order to meet this challenge we have deployed a pilot component-based system in Albuquerque, NM as part of the National Biodefense Initiative (BDI). B-SAFER gathers routinely collected data from healthcare institutions to monitor disease events in the community. We describe initial results from the deployment of the system for the past 6 months

Prevalence and risk factors associated with hepatitis C in ED patients.

The objective of this study was to measure the prevalence of and identify risk factors associated with hepatitis C virus (HCV) in emergency department (ED) patients. Adults presenting to an urban university teaching hospital, having blood drawn as part of their routine evaluation, had an extra tube drawn and tested for HCV. English-speaking adults consenting to participate in the survey portion of the study were administered an in-depth risk factor questionnaire. A case-control analysis was used to identify risk factors in HCV+ compared with HCV- subjects. Contingency table analyses using the Fisher exact test, odds ratios (OR), and 95% confidence intervals (CI) were used for risk factor identification. Of 223 blood samples, 38 (17%) were positive for antibodies for HCV. One hundred twenty-one subjects (54%) agreed to the risk factor survey, 18 (15%) of whom were HCV+. Of the 18 HCV+ survey participants, 12 new diagnoses of HCV were made. A history of injection drug use was the most significant risk factor associated with HCV (OR 858.5, CI 61.8-22,026.5). A high prevalence of HCV is found in selected urban ED patients. Most of these patients have a constellation of risk factors including a history of injection drug use. Efforts to identify at risk patients for serologic testing and follow-up should be initiated. Identifying undiagnosed HCV can lead to interventions to decrease transmission as well as reduce the morbidity and mortality of disease.

Low prevalence of Chlamydia trachomatis by urinary ligase chain reaction in women patients in the emergency department.

UNLABELLED: Recent studies suggest that women with acute urethral syndrome or abdominal pain, presenting to emergency departments (EDs), have a high prevalence of Chlamydia trachomatis. OBJECTIVES: To estimate the prevalence of C. trachomatis in women presenting to an ED and to see whether those with dysuria or abdominal pain have a higher prevalence of C. trachomatis. METHODS: The authors conducted a prospective cross-sectional study of C. trachomatis in the urine of women aged 18 to 50 years who had a urinalysis performed at a university/county ED from February through May 1998. Urine specimens were labeled for the presence of symptoms and analyzed for C. trachomatis by ligase chain reaction (LCR). Polymerase chain reaction (PCR) testing of cervical swabs for C. trachomatis was done for usual clinical indications. Difference in proportions of positive LCR tests among patients was tested with Fisher's exact test. Agreement between PCR and LCR was measured using Cohen's kappa statistic. RESULTS: Of 397 women whose urine was tested, 280 had symptoms of dysuria, abdominal pain, or both, and 117 had no symptoms. The overall prevalence of C. trachomatis by LCR was 3.8% (95% CI = 2.1% to 6.2%); and the combined PCR-LCR prevalence was 4.3% (95% CI = 2.5% to 6.8%). The presence of symptoms was not associated with a positive LCR test for C. trachomatis (p = 0.26, power = 0.8, alpha = 0.05, difference 3% vs. 12%). In the 172 patients who had both a PCR cervical swab and urine LCR, agreement was excellent (kappa = 0.67, 95% CI = 0.45 to 0.90). CONCLUSIONS: This ED had a surprisingly low prevalence of C. trachomatis. Women with symptoms were not more likely to test positive than those without.