Symptom-Based Dispatching in an Emergency Medical Communication Centre: Sensitivity, Specificity, and the Area under the ROC Curve

Background: Measuring the performance of emergency medical dispatch tools used in paramedic-staffed emergency medical communication centres (EMCCs) is rarely performed. The objectives of our study were, therefore, to measure the performance and accuracy of Geneva’s dispatch system based on symptom assessment, in particular, the performance of ambulance dispatching with lights and sirens (L&S) and to measure the effect of adding specific protocols for each symptom. Methods: We performed a prospective observational study including all emergency calls received at Geneva’s EMCC (Switzerland) from 1 January 2014 to 1 July 2019. The risk levels selected during the emergency calls were compared to a reference standard, based on the National Advisory Committee for Aeronautics (NACA) scale, dichotomized to severe patient condition (NACA ≥ 4) or stable patient condition (NACA < 4) in the field. The symptom-based dispatch performance was assessed using a receiver operating characteristic (ROC) curve. Contingency tables and a Fagan nomogram were used to measure the performance of the dispatch with or without L&S. Measurements were carried out by symptom, and a group of symptoms with specific protocols was compared to a group without specific protocols. Results: We found an acceptable area under the ROC curve of 0.7474, 95%CI (0.7448–0.7503) for the 148,979 assessments included in the study. Where the severity prevalence was 21%, 95%CI (20.8–21.2). The sensitivity of the L&S dispatch was 87.5%, 95%CI (87.1–87.8); and the specificity was 47.3%, 95%CI (47.0–47.6). When symptom-specific assessment protocols were used, the accuracy of the assessments was slightly improved. Conclusions: Performance measurement of Geneva’s symptom-based dispatch system using standard diagnostic test performance measurement tools was possible. The performance was found to be comparable to other emergency medical dispatch systems using the same reference standard. However, the implementation of specific assessment protocols for each symptom may improve the accuracy of symptom-based dispatch systems.

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Emergency physician’s dispatch by a paramedic-staffed emergency medical communication centre: sensitivity, specificity and search for a reference standard

Scandinavian Journal of Trauma Resuscitation and Emergency Medicine ◽

10.1186/s13049-021-00844-y ◽

2021 ◽

Vol 29 (1) ◽

Author(s):

Victor Nathan Chappuis ◽

Hélène Deham ◽

Philippe Cottet ◽

Birgit Andrea Gartner ◽

François Pierre Sarasin ◽

...

Keyword(s):

Reference Standard ◽

Medical Systems ◽

Operating Characteristics ◽

First Line ◽

Emergency Calls ◽

Emergency Medical ◽

Dispatch Centre ◽

Second Tier ◽

Low Sensitivity ◽

Level Of Risk

Abstract Background Some emergency medical systems (EMS) use a dispatch centre where nurses or paramedics assess emergency calls and dispatch ambulances. Paramedics may also provide the first tier of care “in the field”, with the second tier being an Emergency Physician (EP). In these systems, the appropriateness of the decision to dispatch an EP to the first line at the same time as the ambulance has not often been measured. The main objective of this study was to compare dispatching an EP as part of the first line emergency service with the severity of the patient’s condition. The secondary objective was to highlight the need for a recognized reference standard to compare performance analyses across EMS. Methods This prospective observational study included all emergency calls received in Geneva’s dispatch centre between January 1st, 2016 and June 30th, 2019. Emergency medical dispatchers (EMD) assigned a level of risk to patients at the time of the initial call. Only the highest level of risk led to the dispatch of an EP. The severity of the patient’s condition observed in the field was measured using the National Advisory Committee for Aeronautics (NACA) scale. Two reference standards were proposed by dichotomizing the NACA scale. The first compared NACA≥4 with other conditions and the second compared NACA≥5 with other conditions. The level of risk identified during the initial call was then compared to the dichotomized NACA scales. Results 97′861 assessments were included. Overall prevalence of sending an EP as first line was 13.11, 95% CI [12.90–13.32], and second line was 2.94, 95% CI [2.84–3.05]. Including NACA≥4, prevalence was 21.41, 95% CI [21.15–21.67], sensitivity was 36.2, 95% CI [35.5–36.9] and specificity 93.2 95% CI [93–93.4]. The Area Under the Receiver-Operating Characteristics curve (AUROC) of 0.7507, 95% CI [0.74734–0.75397] was acceptable. Looking NACA≥5, prevalence was 3.09, 95% CI [2.98–3.20], sensitivity was 64.4, 95% CI [62.7–66.1] and specificity 88.5, 95% CI [88.3–88.7]. We found an excellent AUROC of 0.8229, 95% CI [0.81623–0.82950]. Conclusion The assessment by Geneva’s EMD has good specificity but low sensitivity for sending EPs. The dichotomy between immediate life-threatening and other emergencies could be a valid reference standard for future studies to measure the EP’s dispatching performance.

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How to evaluate an emergency medical dispatch system

European Journal of Emergency Medicine ◽

10.1097/00063110-199509000-00006 ◽

1995 ◽

Vol 2 (3) ◽

pp. 128???135 ◽

Cited By ~ 15

Author(s):

P. CALLE ◽

H. HOUBRECHTS ◽

L. LAGAERT ◽

W. BUYLAERT

Keyword(s):

Emergency Medical Dispatch ◽

Emergency Medical ◽

Dispatch System

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The acceptability of an emergency medical dispatch system to people who call 999 to request an ambulance

Emergency Medicine Journal ◽

10.1136/emj.19.2.160 ◽

2002 ◽

Vol 19 (2) ◽

pp. 160-163 ◽

Cited By ~ 9

Author(s):

A O'Cathain

Keyword(s):

Emergency Medical Dispatch ◽

Emergency Medical ◽

Dispatch System

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The Norwegian Medical Dispatch System and the Norwegian Index for Emergency Medical Dispatch

Notfall + Rettungsmedizin ◽

10.1007/s10049-011-1536-7 ◽

2012 ◽

Vol 15 (4) ◽

pp. 342-346 ◽

Cited By ~ 3

Author(s):

K. Lexow

Keyword(s):

Emergency Medical Dispatch ◽

Emergency Medical ◽

Dispatch System

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How to evaluate an emergency medical dispatch system and identify areas for improvement?

European Journal of Emergency Medicine ◽

10.1097/00063110-199609000-00009 ◽

1996 ◽

Vol 3 (3) ◽

pp. 187-190 ◽

Cited By ~ 2

Author(s):

P CALLE ◽

L LAGAERT ◽

W BUYLAERT

Keyword(s):

Emergency Medical Dispatch ◽

Emergency Medical ◽

Dispatch System

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Abstract 290: Association Between Hourly Call Volume in Emergency Medical Dispatch Center and Dispatcher -Assisted Cardiopulmonary Resuscitation Instruction Time in Out-Of-Hospital Cardiac Arrest

Circulation ◽

10.1161/circ.140.suppl_2.290 ◽

2019 ◽

Vol 140 (Suppl_2) ◽

Author(s):

Jong Hwan Kim ◽

Tae Han Kim ◽

Sang Do Shin ◽

Ki Jeong Hong ◽

Jeong Ho Park ◽

...

Keyword(s):

Logistic Regression ◽

Cardiac Arrest ◽

Regression Model ◽

Logistic Regression Model ◽

Multivariable Logistic Regression Model ◽

Emergency Medical Dispatch ◽

Emergency Calls ◽

Multivariable Logistic Regression ◽

Emergency Medical ◽

Hospital Cardiac Arrest

Objectives: cardiac arrest recognition, ambulance dispatch and dispatcher assisted CPR by emergency medical dispatch (EMD) is crucial for good outcome of out-of-hospital cardiac arrest (OHCA).In EMD, crowding is caused by mismatch between numerous emergency calls and dispatchers per duty available Crowding in emergency department has been shown to decrease the performance and outcome, however little is known about effect of crowding in EMD. We aimed to evaluate incidence of crowding in emergency medical dispatch center and effect of emergency call crowding on dispatcher assisted CPR instruction performance in OHCA calls. Methods: We used nationwide OHCA database from 2013 to 2016, consisted of patients with presumed cardiac origin and dispatched by Seoul EMD. Main exposure was hourly number of total incoming emergency calls to EMD. Number of hourly calls were categorized into quartile (~4o calls, 41~51 calls, 52 ~61 calls and ~62 calls). Primary outcome was successful DA-CPR instruction provision within 120 seconds. Adjusted ratios (AORs) and 95% confidence intervals (CIs) were estimated to evaluate association between EMD crowding and outcome in multivariable logistic regression model. Results: Of a total of 12,722 patients, proportion of successful DA instruction were highest in least crowded quartile and lowest in the most crowded quartile (22.7% vs. 15.o% , p<0.01). The adjusted odds ratios is 0.85 (95% CI 0.74 - 0.98) in most crowded EMD quartile with lesser proportion of DA instruction within 120 seconds. Crowding quartile 4 and quartile 3 was associated lesser favorable neurological outcome in multivariable logistic regression model.(adjusted OR(95% CI) 0.78 (0.60-0.99) and 0.70 (0.54- 0.91) respectively) . Conclusion: Crowding in emergency medicine dispatch caused by increased hourly call volume was associated with delayed dispatcher assisted CPR instruction provision. Medical directors might consider strategy approach to solve crowding in EMD according to crowding distribution.

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