Primary Triage in a Mass-casualty Event Possesses a Risk of Increasing Informational Confusion: A Simulation Study Using Shannon's Entropy.

UNLABELLED: Introduction Primary triage in a mass-casualty event setting using low-visibility tags may lead to informational confusion and difficulty in judging triage attribution of patients. In this simulation study, informational confusion during primary triage was investigated using a method described in a prior study that applied Shannon's Information Theory to triage. Hypothesis Primary triage using a low-visibility tag leads to a risk of informational confusion in prioritizing care, owing to the intermingling of pre- and post-triage patients. It is possible that Shannon's entropy evaluates the degree of informational confusion quantitatively and improves primary triage.
METHODS: The Simple Triage and Rapid Treatment (START) triage method was employed. In Setting 1, entropy of a triage area with 32 patients was calculated for the following situations: Case 1 - all 32 patients in the triage area at commencement of triage; Case 2 - 16 randomly imported patients to join 16 post-triage patients; Case 3 - eight patients imported randomly and another eight grouped separately; Case 4 - 16 patients grouped separately; Case 5 - random placement of all 32 post-triage patients; Case 6 - isolation of eight patients of minor priority level; Case 7 - division of all patients into two groups of 16; and Case 8 - separation of all patients into four categories of eight each. In Setting 2, entropies in the triage area with 32 patients were calculated continuously with each increase of four post-triage patients in Systems A and B (System A - triage conducted in random manner; and System B - triage arranged into four categories).
RESULTS: In Setting 1, entropies in Cases 1-8 were 2.00, 3.00, 2.69, 2.00, 2.00, 1.19, 1.00, and 0.00 bits/symbol, respectively. Entropy increased with random triage. In Setting 2, entropies of System A maintained values the same as, or higher than, those before initiation of triage: 2.00 bits/symbol throughout the triage. The graphic waveform showed a concave shape and took 3.00 bits/symbol as maximal value when the probability of each category was 1/8, whereas the values in System B showed a linear decrease from 2.00 to 0.00 bits/symbol.
CONCLUSION: Informational confusion in a primary triage area measured using Shannon's entropy revealed that random triage using a low-visibility tag might increase the degree of confusion. Methods for reducing entropy, such as enhancement of triage colors, may contribute to minimizing informational confusion. Ajimi Y , Sasaki M , Uchida Y , Kaneko I , Nakahara S , Sakamoto T . Primary triage in a mass-casualty event possesses a risk of increasing informational confusion: a simulation study using Shannon's entropy. Prehosp Disaster Med. 2016;31(5):498-504.