Ensuring the provision of effective and safe healthcare within the out-of-hospital environment is an enduring challenge for healthcare professionals. This issue has received considerable attention within North American and European contexts, perhaps attributable to these regions’ established and comprehensive prehospital EMS systems. Moreover, the literature reviewed herein dissected three primary theoretical frameworks that underpin decisions of patient non-transportation: DID, CID, and PIR.

These decision-making mechanisms collectively shape the landscape of patient non-transport decisions in prehospital care. The juxtaposition of these diverse theories underscores the multifaceted and complex nature of non-transport decisions. It hints at the necessity for a nuanced understanding incorporating the varied elements of prehospital care environments.

Utilizing a standardized computerized system in the triage and management of pre-hospital emergency calls can notably diminish error rates, bolstering quality management and assurance. EMDs often employ a computer-aided dispatch (CAD) system to enhance their decision-making processes, ensuring the expedited dispatch of the most appropriate ERUs. This system undergoes consistent regulation and enhancement, with its performance benchmarks often tethered to the best-performing global EMS systems. A select number of ambulance services employ a computerized medical dispatch system to adeptly manage pre-hospital emergency calls [14, 15], known as the MPDS [16]. MPDS is a computer-based pre-hospital categorization system that can be utilized to optimize the management of pre-hospital cases. It facilitates allocating and dispatching the most appropriate pre-hospital ERU according to the patient’s chief complaints. MPDS enables EMDs to dispatch an ERU staffed with a responder with the required level of skills. This helps avoid delays in providing emergency treatment [17]. A recent study from Finland demonstrated that 40% of emergency calls resulted in patient non-transport decisions; 37.7% of these were aborted by the EMD before the ERU reached the patient [18]. This could be due to causes related to the caller or the EMD.

Additionally, there are instances where the caller decides that EMS assistance is no longer necessary. For example, in some instances, the patient improved or managed their own transportation to the hospital while the EMD still gathered information and processed the case through ProQA. In certain instances, following a comprehensive assessment using ProQA, the EMDs may advise the caller that it is appropriate for the patient to proceed to the nearest healthcare facility using their own means of transportation, if necessary. This is observed in cases where the patient is “not fulfilling” the requirements of an emergency medical condition that mandates immediate pre-hospital medical assistance. Examples of such cases include “asymptomatic hypertension”, “waters were broken for a pregnant woman with no contractions”, or “fever” [19].

MPDS facilitates the EMD going through a detailed medical questionnaire process. This enables them to determine the appropriate protocol and dispatch code according to the information provided by the caller about the patient’s condition. An expert panel continually updates the MPDS using emergency calls from the databases of the best-performing ambulance services worldwide [20]. The determined dispatch code dictates which type of medical or non-medical ERU should be dispatched [20]. A quality improvement study conducted in the USA included cases triaged by the EMDs as not requiring a medical ERU. In such cases, the EMD could dispatch a “non-transport unit.”

Furthermore, based on information provided by the emergency caller and the dispatch code determined by MDPS, the EMD may decide that the dispatch of a highly equipped ERU staffed with advanced healthcare professionals is not required in some instances [21]. Subsequently, they may dispatch a “non-transport unit” as a follow-up unit for patients with minor medical complaints. In a recent study in New York, the researchers demonstrated that the reasons leading to the cancelation of the ERU could be determined based on the information gathered by the EMD during the emergency call process [22]. Occasionally, the caller ends the emergency call without calling back or answering the EMD’s calls [22]. Multiple studies have reported this non-transport by DID [23,24,25,26,27,28]. Recent systematic reviews have investigated the efficacy of EMS systems utilizing the MPDS and other EMS systems utilizing criteria-based dispatch (CBD). However, published evidence regarding the efficacy of these medical dispatch systems is lacking [1]. Healthcare professionals in some EMS systems under-triaged patients requiring critical care but appropriately identified cases of cardiac arrest [29]. This suggests that not transporting a patient following an emergency call might sometimes be risky.

Several other studies have demonstrated that these systems also under-triage some stroke cases. This is because some of these patients are older adults presenting with non-specific conditions (NSC) which might then be encoded as “sick person” [1]. Other studies have demonstrated that the dispatch code determined by these systems for trauma cases is inconsistent with the patient assessment findings observed by the medical responders [1, 30]. Researchers have also suggested that the anatomical presentation in the dispatch system’s questionnaire would be more effective if appropriately matched with the paramedics’ assessment [30]. In addition, these systems over-triage chest pain, cardiac problems, and complaints of headache [1]. A UK-based study reported that only 5% of priority one dispatch calls with these mentioned complaints were identified as critical [31]. This indicates that EMS resources could be wasted in 95% of non-critical cases that probably did not require conveyance to the emergency department.

Clinical determinations enacted by the evaluating medical practitioner may occasionally culminate in a non-transport decision for the patient, a scenario commonly referred to as CID. ‘Non-conveyance’ according to clinician discretion is an outcome that has been cited in many studies (n = 15) [18, 23,24,25,26, 28, 32,33,34,35,36,37,38,39,40]. In some instances, non-conveyance represents a clinical verdict enacted by EMS personnel subsequent to their response to an emergency call and the subsequent provision of emergency care to the patient. Consequently, upon the clinical assessment, the responder possesses the discretion to ascertain whether the patient is enduring a non-significant medical condition, obviating the necessity for immediate emergency treatment within a hospital setting. As a result, the patient may not be transported to the hospital.

Notwithstanding, these individuals may be advised to pursue additional medical assistance from an alternate, non-emergency healthcare service or provider. This non-conveyance system has seen widespread adoption among various ambulance services globally [16]. This approach aids in averting unwarranted ambulance conveyances to the hospital for medical conditions that can be effectively addressed in alternate settings, encompassing primary healthcare centers, thereby reducing the undue burden on emergency departments [41]. This system helps avoid emergency department crowding [7, 23, 42, 43].

Nonetheless, the EMS systems adopting this procedure monitor these non-conveyance patients closely by contacting some of them later for follow-up. Non-conveyance rates are also used as a quality indicator within these systems [23, 42, 43]. Furthermore, studies have demonstrated that serious cases might sometimes be miss-triaged as non-conveyance, specifically in older adult patients [44]. A recent study from Sweden demonstrated that NSC is mainly related to older patients. These patients were generally present with stable vital signs. Also, they reported complaints of “affected general health condition,” “general malaise,” “sense of illness,” or “just being unable to cope with daily activities” without providing a more specific chief complaint [44].

Consequently, these patients might be triaged as not requiring critical care. However, they might experience serious health outcomes without immediate treatment and care. Previous studies in the EMS setting have reported that at least one in three NSC patients presented with a serious health issue requiring close hospital monitoring [45, 46].

The non-transport decision can also stem from PIR [18, 27, 36, 47,48,49,50,51,52,53,54,55,56,57]. Contemporary studies have illuminated instances where, within numerous EMS systems, patients elect not to be conveyed to the hospital, against clinical advice [56]. In specific EMS systems, for example, in the USA, pre-hospital healthcare workers can acknowledge the PIR only after an online consultation with the medical management team [33, 58]. These PIRs are frequently correlated with a patient’s incapacity to shoulder prospective transport fees, especially in specific jurisdictions where the individual bears such costs. Additional deterrents encompass protracted wait times encountered within the emergency department. In some instances, PIRs are precipitated by patient contentment with the caliber of pre-hospital medical assistance they receive, juxtaposed against their dissatisfaction with the drawn-out procedural rigmarole anticipated at the emergency department [7, 56, 59, 60]. In a recent Middle-East study conducted by the National Ambulance Service of Riyadh, 35.5% of the pre-hospital emergency calls ended with PIR, compared with only 8.8% of patient non-conveyance due to CID [56].

Psychological considerations also significantly come into play, particularly with elderly patients who might harbor apprehension towards polypharmacy. As a result, physicians encounter challenges when prescribing a higher quantity of medications, sometimes as much as 25 pills, for older adults and persuading them to return home when everything seems to be in order [61]. Furthermore, a Swedish study demonstrated that with the increase in the age of patients visiting emergency departments for emergency care, hospitalization, and mortality rates also increase. This is because, in some instances, older patients only visit the emergency department when their medical condition becomes critical [62]. Therefore, many health systems worldwide have recognized the impact of patient non-transport, both for the health outcomes of older adult patients and as a quality indicator in EMS systems. They also reflect a significant challenge that could compromise patients’ health conditions in major and minor trauma cases [63]. Some concerns about the non-conveyance of older patients have been expressed since they can be easily under-triaged. Many older patients not transported to the hospitals, called the emergency services again, and were eventually transported and admitted to the hospital [45, 46, 64]. Some recent studies have focused on the non-conveyance of elderly trauma victims. With their vulnerable physio-pathological conditions, older patients can present with significant trauma even after incidents with low-impact mechanisms. Older patients might also be often misdiagnosed [46].

Meta-analyses have demonstrated that patient non-conveyance mainly affects younger than older patients [64, 65]. Furthermore, these studies have indicated that more than a quarter of the non-transported patients accessed alternative healthcare service providers other than those working in emergency departments (e.g., private clinics) [64].

Inferences drawn from a comprehensive examination of prior studies reveal that specific EMS systems have integrated the concept of patient non-conveyance into their guidelines. They deem it a practice with an acceptable level of risk, contingent on initiating a telephonic medical consultation or deploying follow-up units for non-conveyance cases [32, 38, 49, 66]. Notably, the term ‘acceptable’ risk elicits diverse interpretations across the literature [37, 38, 50, 67]. There is a latent risk of under-triage, potentially leading to overlooked life-threatening complaints. This is especially pertinent for elderly patients, who might necessitate urgent medical attention within a brief interval [39, 50].

As such, the predominant perception within EMS systems classifies patient non-conveyance to a hospital as an adverse event that could compromise their health outcomes [25, 37,38,39, 48, 51, 53, 65, 68].

In light of these observations, we concur with the call for precautionary patient transportation to hospitals or implementing a reliable medical follow-up mechanism. It is crucial to clarify that this conclusion hinges on our interpretation of the reviewed literature and advocates for further empirical exploration.

Our study recognizes and acknowledges its intrinsic limitations. Primarily, our investigative approach is a narrative review instead of a systematic exploration of the extant literature. This method, though enabling an encompassing overview of the subject matter, is potentially susceptible to selection bias during the process of literature analysis, which may engender considerable distortions in our resultant findings. Second, the non-conveyance decisions reported in the literature could be affected by factors such as the worldwide diversity of the EMS operational systems. This could also affect the proportion of non-conveyance decisions. Further, generalizing the non-conveyance theories could be difficult as it is also affected by many social, ethnic, and cultural factors and the diversification of worldwide EMS systems. The widespread diversity in policy and practice inherently constrains the universal applicability of our observations and recommendations. As such, we advocate for future research to engage in a more systematic review methodology. Such an approach could help address these potential biases and facilitate a more thorough comprehension.