Non-conveyance in the ambulance service: a population-based cohort study in Stockholm, Sweden.

Objectives: Non-conveyed patients represent a significant proportion of all patients cared for by ambulance services in the western world. However, scientific knowledge on non-conveyance is sparse. Therefore, the aim of this study was to describe the prevalence of non-conveyance, investigate associations and compare patients' characteristics, drug administration, initial problems and vital signs between non-conveyed and conveyed patients.

Design: A population-based retrospective cohort study.

Setting: The study setting area, Stockholm, Sweden, has a population of 2.3 million inhabitants, with seven emergency hospitals. Annually, approximately 210 000 assignments are performed by 73 ambulances. All ambulance assignments performed from 1 January to 31 December 2015 were included.

Results: In total, 23 603 ambulance assignments ended in non-conveyance-13.8% of all ambulance assignments performed in 2015. Compared with conveyed patients, non-conveyed patients were younger and more often female (median age 50.1 years for non-conveyed vs 61.7 years for conveyed; female=52 %, both p values <0.001). Approximately half of all ambulance assignments ending in non-conveyance were initially prioritised and dispatched as the highest priority. Non-conveyed patients were more often assessed by ambulance clinicians as presenting non-specific symptoms or symptoms related to psychiatric problems. Low blood glucose levels were highly associated with non-conveyance (adjusted OR (AOR): 15; 95 % CI 11.18 to 20.13), although non-conveyed patients presented abnormal vital signs across all categories of vital signs. Moreover, drugs were more often administered to younger non-conveyed patients. Older patients were more often conveyed and administered drugs once conveyed (AOR: 1.29; 95 % CI 1.07 to 1.56).

Conclusions: This study shows that non-conveyed patients represent a non-negligible proportion of all patients in contact with ambulance services. In general, most cases of non-conveyance occur at the highest dispatch level, to a large extent involve younger patients, and features problems assessed by ambulance clinicians as non-specific or related to psychiatric symptoms.