The Ability of Emergency Medical Dispatch Codes of Medical Complaints to Predict ALS Prehospital Interventions

Abstract

Objective. The Medical Priority Dispatch System (MPDS) is an emergency medical dispatch (EMD) system that is commonly used to triage 9-1-1 calls andoptimize paramedic andEMT dispatch. The objective of this study was to determine the sensitivity, specificity, andpositive andnegative predictive values of selected MPDS dispatch codes to predict the need for ALS medication or procedures. Methods. Patients with selected MPDS codes between November 1, 2003, andOctober 31, 2005, from a suburban California county were matched with their electronic patient care record. The records of all transported patients were queried for prehospital interventions andmatched to their MPDS classification [Basic Life Support (BLS) versus Advanced Life Support (ALS)]. Patients who received prehospital interventions or medications were considered ALS Intervention. With true positive = ALS by MPDS + ALS Intervention, true negative = BLS by MPDS + BLS Interventions, false positive = ALS by MPDS + BLS Interventions, andfalse negative = BLS by MPDS + ALS Interventions, the screening performance of the San Mateo County EMD system was determined for selected complaint categories (abdominal pain, breathing problems chest pain, sick person, seizures, andunconscious/fainting). Results. There were a total of 64,647 medical calls, and42,651 went through the EMD process; 31,187 went through the EMD process andwere transported; 22,243of these were matched to a patient care record. The sensitivity andspecificity with 95% confidence intervals in () were as follows: all EMD calls 84 (83–85), 36 (35–36); abdominal pain, 53 (41–65), 47 (43–51); chest pain 99 (99–100), 2 (1–3); seizure 83 (77–88), 20 (17–23), sick 59 (53–64), 51 (49–54), andunconscious/fainting 99 (98–100), 2 (2–3). Conclusion. In our EMS system, MPDS coding for all medical calls had high sensitivity andlow specificity for the prediction of calls that required ALS intervention. Chest pain andunconscious/fainting calls were screened with very high sensitivity but very low specificity.