IntroductionPrevious studies have described the difficulties and the complexity of assessing an emergency call, and assessment protocols intended to support the emergency medical dispatcher’s (EMD) assessment have been developed and evaluated in recent years. At present, the EMD identifies about 50-70 % of patients suffering from cardiac arrest, acute myocardial infarction or stroke. The previous research has primarily been focused on specific conditions, and it is still unclear whether there are any overall factors that may influence the assessment of the call to the emergency medical communication centre (EMCC).AimThe aim of the study was to identify overall factors influencing the registered nurses’ (RNs) assessment of calls to the EMCC.MethodA qualitative study design was used; a purposeful selection of calls to the EMCC was analysed by content analysis.ResultsOne hundred calls to the EMCC were analysed. Barriers and opportunities related to the RN or the caller were identified as the main factors influencing the RN’s assessment of calls to the EMCC. The opportunities appeared in the callers’ symptom description and the communication strategies used by the RN. The barriers appeared in callers’ descriptions of unclear symptoms, paradoxes and the RN’s lack of communication strategies during the call.ConclusionBarriers in assessing the call to the EMCC were associated with contradictory information, the absence of a primary problem, or the structure of the call. Opportunities were associated with a clear symptom description that was also repeated, and the RN’s use of different communication strategies such as closed loop communication.