Ability of the Medical Priority Dispatch System Protocol to predict the acuity of "Unknown Problem" dispatch response levels

Objective. To determine if Medical Priority Dispatch System's (MPDS's) Protocol 32-Unknown Problem interrogation-based differential dispatch coding distinguishes the acuity of patients as found at the scene by responders, when little (if any) clinical information is known. Methods. "Unknown problem" situations (i.e., all cases not fitting into any other chief complaint group) constitute 5-8% of all calls to dispatch centers. From the total patient encounters (n = 599,107) in the aggregate data of one year (September 2005 to August 2006), we examined 3,947 (0.7%) encounters initially coded as "unknown problem" by the London Ambulance Service Communications Center for the scene presence of cardiac arrest (CA) and paramedic-determined high-acuity (blue-in [BI]/"lights and siren") findings. Odds ratios (ORs) with 95% confidence intervals (95% CIs) and p-values were used to assess the degree of associations between determinant codes and case outcomes (i.e., CA/BI). Results. Statistically significant association between clinical dispatch determinant codes and case outcomes was observed in the "life status questionable" (LSQ; DELTA-1 [D-1]) and the "standing, sitting, moving, or talking" (BRAVO-1 [B-1]) code pair for the CA outcome (OR [95% CI]: 0.11 [0, 0.63], p = 0.005) and for the BI outcome (OR [95% CI]: 0.47 [0.28, 0.77], p = 0.003). The LSQ and all three BRAVO code pairs (i.e., B-1;" community alarm notifications" [B-2]; and "unknown status" [B- 3]) also demonstrated significant associations both with the CA outcome(OR [95% CI]: 0.43 [0.23, 0.81], p = 0.010) and with the BI outcome OR [95% CI]: 0.74 [0.56, 0.97], p = 0.033). All the determinant code levels yielded significant association between BI and CA cases. Conclusion. This dispatch protocol for unknown problems successfully differentiates dispatch coding of low-acuity and non-CA patients only when specific situational information such as the patient's standing, sitting, moving, or talking can be determined during the interrogation process. Also, emergency medical dispatcher (EMD) reliance on caller-volunteered information to identify predefined critical situations does not appear to add to the protocol's ability to differentiate high-acuity and CA patients. LSQ proved to be a better predictor of both CA and BI outcomes, when compared with the BRAVO-level determinant codes within the "unknown problem" chief complaint. The B-3 (completely unknown) determinant code is a better predictor of severe outcomes than nearly all of the clinically similar BRAVO determinant codes in the entire MPDS protocol. Hence, the B-3 coding should be considered-in terms of its predictability for severe outcome-as falling somewhere between a typical DELTA and a typical BRAVO determinant code.