Definitions of the variables of interest
| Variables of interest | Definition |
| Age | The biological age of the patient at the time of the interaction with AV. Categorised into 5-year increments to 90 years. |
| Gender | The biological sex of the patient. Categorised as male and female. |
| Primary diagnosis | The final paramedic diagnosis category recorded in ePCR following paramedic clinical assessment. These are a broad symptom groups. |
| Local Government Area (LGA) | Identified through patient residential postcodes. The median income for each LGA reported by the Australian Bureau of Statistics was used to compare the LGA median income to the median income of all metropolitan Melbourne in 2011/2012 as a proxy for socioeconomic status. LGAs were classed has being ‘above’ or ‘below’ the median income of metropolitan Melbourne. |
| Vital signs | The physiological measurements obtained by paramedics. Vital signs were classed as ‘normal’ or ‘abnormal (low or high)’ as indicated below. The vital signs were categorised as follows: |
| Initial pulse rate (beats/min): 0–59 (abnormal - low), 60–99 (normal) and 100–248 (abnormal - high) | |
| Systolic blood pressure: 0–99 (abnormal - low), 100–139 (normal) and 140 and above (abnormal - high) | |
| Glasgow Coma Scale: 3–9 (abnormal), 10–14 (abnormal) and 15 (normal) | |
| Time of day | Aligned with the common paramedic ‘day-shift ‘of 0700–1700 hours or ‘night-shift’ of 1700–0700 hours |
| Weighted Charlson Comorbidity Index (WCCI) | The WCCI is a method of categorising comorbidities using the International Classification of Diseases diagnosis codes. The comorbidity categories are weighted from 1 to 6 based on the adjusted risk of mortality or resource use. The comorbidity score is the sum of all the weights. The WCCI was calculated and categorised using methods published by Charlson et al.23 |
| Highest dispatch code | Code 1: immediate emergency ambulance dispatch using lights and sirens; arrival at the case within 15 min. |
| Code 2: immediate emergency ambulance dispatch with no lights or sirens. Obey all road rules and arrive within 25–30 min. | |
| Code 3: low-acuity dispatches, arrival to the patient within 60 min. Ambulance will be diverted if a more acute case arises closer to them | |
| Initial pain score | During clinical assessment, patients were asked to rank any pain on a continuous scale of 0–10, categorised as: |
| 0 (no pain) | |
| 1–2 (mild: does not require treatment) | |
| 3–6 (medium: requires treatment) and | |
| 7–10 (high: requires treatment) |
ePCR, electronic patient care record.