The main findings of this study were as follows. Firstly, 4 in 5 (83.9% in 0–24 h) of non-conveyed patients had no adverse events after the non-conveyance mission. Secondly, patients were mainly in good condition; the NEWS2 scores were low and duration of visits to primary health care or EDs short. The reasons for the adverse events seem to be different than the reason for the initial EMS mission. Thirdly, 0.03% of the non-conveyance decisions seem to be related to a patient’s death, where re-evaluation showed poor clinical judgement and/or clinical treatment protocol violation.
From the perspective of patient safety, it is important that the majority of non-conveyed patients did not have any subsequent events during the follow-up period, which is in line with previous studies [21, 31]. We found that EMS re-contacts, visits to primary health care or ED and hospitalization were relatively rare after non-conveyance missions. Two previous reviews indicate that there are many studies focusing on specific populations in which the sample size is small or the follow-up is by telephone, which may lead to bias because the follow-up of a large number of patients may fail [5, 17]. Thus, comparisons with our findings are challenging. However, the subsequent event rates in this study were roughly the same as in other similar studies [21, 31].
Our study indicates that the 24-h period after an EMS visit seems to be critical. The highest incidence of all outcomes occurred within 0–24 h after the initial non-conveyance mission, which was noted previously . A longer follow-up period could have provided more information, but the likelihood of an adverse event being due to some other reason would have increased.
Our study shows that, in the case of EMS re-contact, primary health care or ED attendance, and hospitalization, the patients were mainly in good condition. The new mission (EMS re-contact) was commonly non-urgent, the patients’ NEWS2 scores were low, and almost half of these cases ended in a new non-conveyance decision. The visits to primary health care facilities or EDs were mostly short. On the other hand, 32 patients (0.3%) needed intensive care and 62 patients (0.5%) were treated in high-dependency units after the initial non-conveyance case. These findings are similar to a Swedish study . However, it is difficult to assess whether these patients’ critical condition was derived from the EMS’s poor clinical judgement and incorrect non-conveyance decision. When comparing the preliminary diagnosis (adjusted ICPC2) to new ICPC2 codes in case of EMS re-contact or discharge diagnoses (ICD10) from primary health care, ED, or after hospitalization, these adverse events were usually not related to the initial non-conveyance mission. In addition, we found that there were many subsequent visits to primary health care, which may be an indication of impaired access to primary health care, especially in the evening and at night.
Our logistic regression model (Table 7) and previous studies [21, 32] indicate that older age is a risk factor for adverse outcomes. This may be due to elderly patients’ complex symptoms and many comorbidities and medications. We also found that patients’ refusal of conveyance and the use of alcohol predicted an EMS re-contact in 0–24 h. One explanation may be that these patients do not know how to handle their problems and an EMS re-call is the easiest choice. Other studies have reported that the refusal is associated with ED visits  and alcohol increases the likelihood of non-conveyance .
Decision-making at night is challenging . Our results show that EMS arrival at night increases the likelihood of 3 in 4 primary outcomes of this study. However, the end of a work shift was not associated with re-contacts, which may indicate that EMS providers consider the patient’s needs even though the shift is close to its end. However, EMS arrival at night, non-urgent mission, ALS unit, rural area, and longer distance to a health care facility or ED were related to subsequent visits to primary health care. There is a possibility that this demonstrates appropriate use of health care resources to avoid unnecessary conveyance to the ED. Geographic variation in the EMS context is high , but the impact of geography on a patient’s outcome is unclear. However, the on-scene time is reported to be high in rural areas  and in the case of non-conveyance . Understandably, visits to primary health care were related to non-urgent missions. In contrast, it seems that EMSs can safely discharge urgent missions such as hypoglycemia and other chronic diseases at the scene after appropriate assessment and treatment. Previous studies have shown that non-conveyance is challenging and requires competence [5, 34]. Indeed, there are a number of factors that are related to non-conveyance decisions [3, 8, 37,38,39]. Our study demonstrated that ALS units are associated with re-contact in primary health care. This may be due to the longer education of EMS care providers in ALS units, which may be associated with more appropriate decision-making related to the use of primary health care and ED resources. On the other hand, based on the univariate analyses, BLS units increased the risk of subsequent ED visits. This raises the question of whether these visits are related to the BLS units’ competence. However, more studies are needed.
Moreover, an Australian study indicated that, when the EMS discharged patients at the scene, there was an increased risk of adverse events compared to patients discharged from the ED . Notably, subsequent contacts with health care do not automatically mean that patient safety is compromised [5, 30].
Abnormal vital signs have been found as a common predictor of adverse events after EMS non-conveyance . We found that, if the patient’s NEWS2 score increases by 1 point or the score is high (> 7 points), the risk of EMS re-contact increases. Non-specific complaints lead to a number of adverse outcomes in both the EMS context and EDs [19, 20, 40]. Surprisingly, we did not find similar results. Based on univariate analyses, non-specific complaints were only related to EMS re-contact in 24–48 h.
This study has several limitations, three of which were described previously (excluded patients, the use of adjusted ICPC2 classification, and NEWS2 score calculation) .
The register of ED visits included the date, but the exact visit time was mainly missing. Thus, the initial non-conveyance case was judged to have occurred first and the 0–24 h ED visit to have occurred on the same day or the following day. Furthermore, the register of visits to primary health care includes chronic disease monitoring. Therefore, the rate of visits to primary health care and EDs for real adverse events after the non-conveyance mission may be lower. On the other hand, some patients may have sought further care at private clinics, but all patients with severe or even moderate deterioration would have been sent to an ED.
The reasons for care (adjusted ICPC2) were compared to the discharge diagnoses (ICD10) from the primary health care facilities or EDs or to diagnoses after hospitalization in order to determine whether these events were related to the initial non-conveyance mission. Notably, the ICPC2 chosen by EMSs is based on symptoms and signs present at the time of the EMS contact. The time between ICPC2 and discharge diagnosis, further examination, and the treatment given may affect the discharge diagnosis. Thus, the real rate of adverse events due to the same reason as the initial non-conveyance case may be higher.
Only unexpected deaths were analyzed, and therefore patients with end of life decisions were excluded. However, it is possible that this approach did not identify all of these patients due to missing information. When assessing the risk factors for adverse events, 28-day mortality and hospitalization in 24–48 h were excluded from our multivariable logistic regression model as dependent variables because these events were very rare in our data set.
In Finland, EMSs and EDs are encouraged to plan emergency patient pathways together. Therefore, triaging and assessing the need for conveyance and non-conveyance decisions are commonly made by the EMS. This practice and the level and scope of education differs between countries; therefore, the generalizability of the results may be limited .