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

OBJECTIVE: The Medical Priority Dispatch System (MPDS) is an emergency medical dispatch (EMD) system that is commonly used to triage 9-1-1 calls and optimize paramedic and EMT dispatch. The objective of this study was to determine the sensitivity, specificity, and positive and negative 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, and October 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 and matched 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, and false 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, and unconscious/fainting). RESULTS: There were a total of 64,647 medical calls, and 42,651 went through the EMD process; 31,187 went through the EMD process and were transported; 22,243 of these were matched to a patient care record. The sensitivity and specificity 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), and unconscious/fainting 99 (98-100), 2 (2-3). CONCLUSION: In our EMS system, MPDS coding for all medical calls had high sensitivity and low specificity for the prediction of calls that required ALS intervention. Chest pain and unconscious/fainting calls were screened with very high sensitivity but very low specificity.