Prehospital triage accuracy in a criteria based dispatch centre.
BACKGROUND
Priority dispatch accuracy is a key issue in optimizing the match between patients' medical needs and pre-hospital resources. This study measures the accuracy of a Criteria Based Dispatch (CBD) system, by evaluating discrepancies between dispatch priorities and ambulance crews' severity evaluations.


METHODS
This is a retrospective study conducted from January 2011 to December 2011. We ruled that a National Advisory Committee for Aeronautics (NACA) score > 3 (injuries/diseases which can possibly lead to deterioration of vital signs) to 7 (lethal injuries/ diseases) should require a priority dispatch with lights and siren (L&S), while NACA scores < 4 should require a priority dispatch without L&S. Over triage was defined as the proportion of L&S dispatches with a NACA score < 4, and under triage as the proportion of dispatches without L&S with a NACA score > 3.


RESULTS
There were 29,008 primary missions in 2011, 1122 were excluded. Of the 15,749 L&S missions, 12,333 patients had a NACA score < 4, leading to an over triage rate of 78 %; 561 missions out of 12,137 missions without L&S had a NACA score > 3, leading to an under triage rate of 4.6 %. Sensitivity was 86 % (95 % confidence interval: 85.6-86.4 %), specificity 48 % (47.4-48.6 %), positive predictive value 21.7 % (21.2-22.2 %), and negative predictive value 95.4 % (95.2-95.6 %).


CONCLUSIONS
The rates of over triage and under triage in our CBD are 78 and 4.6 % respectively. The lack of consistent or universal metrics is perhaps the most important limitation in dispatch accuracy research. This is mainly due to the large heterogeneity of dispatch systems and prehospital emergency system.
Dispatch centre, State of Vaud (Fondation Urgences-Santé), César-Roux 31, 1005, Lausanne, Switzerland. Fabrice.dami@chuv.ch.|Department of Emergency Medicine, University Hospital Center (CHUV), Bugnon 46, 1011, Lausanne, Switzerland. Fabrice.dami@chuv.ch.
Fabrice
F
Dami
Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland. Christel.golay@unil.ch.
Christel
C
Golay
Department of Emergency Medicine, University Hospital Center (CHUV), Bugnon 46, 1011, Lausanne, Switzerland. Mathieu.pasquier@chuv.ch.
Mathieu
M
Pasquier
Dispatch centre, State of Vaud (Fondation Urgences-Santé), César-Roux 31, 1005, Lausanne, Switzerland. Vincent.fuchs@urgences-sante.ch.
Vincent
V
Fuchs
Department of Emergency Medicine, University Hospital Center (CHUV), Bugnon 46, 1011, Lausanne, Switzerland. Pierre-nicolas.carron@chuv.ch.
Pierre-Nicolas
PN
Carron
Department of Emergency Medicine, University Hospital Center (CHUV), Bugnon 46, 1011, Lausanne, Switzerland. Olivier.hugli@chuv.ch.
Olivier
O
Hugli
D019985:Benchmarking / Q000706:statistics & numerical data*; D004632:Emergency Medical Services / Q000379:methods* / Q000592:standards / Q000706:statistics & numerical data*; D006302:Health Services Research; D006305:Health Status Indicators; D006801:Humans; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013557:Switzerland; D014218:Triage / Q000379:methods* / Q000592:standards / Q000706:statistics & numerical data*