The Medical Priority Dispatch System's ability to predict cardiac arrest outcomes and high acuity pre-hospital alerts in chest pain patients presenting to 9-9-9.

Objective: To establish emergency medical dispatcher (EMD) predictability of cardiac arrest (CA) and high acuity (blue in - BI) outcomes in chest pain patients by using the Medical Priority Dispatch System's (MPDS) priority levels, and its more specific clinical determinant codes.

Methods: A retrospective descriptive study was done on a one year's worth of aggregate 999 call data comprising number of patients, calls, incidences, and outcomes (as determined by paramedics) obtained from the London Ambulance Service (LAS). We used Fisher's exact test to establish and quantify associations (through odds ratios, 95% CI and p-values) between MPDS priority levels and patient outcomes, stratifying by various pairing of MPDS priority level determinant codes.

Results: 11.4% of the total calls were classified under the chest pain protocol (MPDS protocol 10). Of all the CA cases (n=3377), 3.1% (n=106) were classified under the chest pain protocol. MPDS priority levels were significantly associated with CA patient outcome (p=0.030) and BI patient outcome (p<0.001). Only the advanced life support response-levels CHARLIE/DELTA pairing was significantly associated with CA outcome (p=0.010) with CA outcome nearly twice more likely in the combined DELTA-priority level codes. ALPHA/CHARLIE and ALPHA/DELTA-level pairings were significantly associated with BI outcome (p<0.001 each), with increased odds of BI outcome in the CHARLIE and DELTA-priority levels. Clinically, the DELTA-level 4 code demonstrated reduced odds of CA and BI outcome when paired with CHARLIE-level patients, than the other DELTA-level patients.

Conclusions: Significant associations existed between patient outcomes, as measured in this study, and the MPDS (UKE version) Protocol 10 (Chest Pain) priority levels and specific determinant codes. The (UKE version) DELTA-level 4 determinant code does not belong in the DELTA-priority level, and should be moved to the CHARLE-level, or eliminated altogether--to bring this protocol version in line with other international versions of the MPDS.