Predictive Value of Witness-derived Secondary Cincinnati Prehospital Stroke Scale Scores in Suspected Stroke

Study Design

• Prospective, analytical, cross-sectional validation study
• Conducted in the Emergency Department of a tertiary academic hospital in Türkiye Two phases

1. Phase 1: Interrater reliability assessment: Between a senior emergency medicine (EM) resident and an emergency medicine (EM) attending physician
2. Phase 2:

Predictive validity assessment The association between secondary CPSS scores, witness demographic characteristics, and decision delays

Phase 1:

Inter-rater agreement between a senior EM resident and an EM attending was assessed using CPSS scoring based on the same witness reports. All witness interviews were conducted face-to-face by trained emergency physicians during the initial ED evaluation. Independent, blinded scoring was performed using CPSS items (0-3 points). Agreement was quantified through percent agreement and Cohen's κ statistics.

Phase 2:

Secondary CPSS scores were compared to final radiological diagnoses. This study investigates the usability and clinical value of witness-derived CPSS scoring through structured interviews conducted by emergency physicians. Given that witnesses are often the first observers of neurological deficits, their descriptions may play a substantial role in early stroke recognition. Recognition-to-action time (decision delay) was obtained from structured witness questionnaires. Witness demographics were recorded.

Data collection used two research forms (RF: RF-1 for reliability assessment; RF-2 for BT/MRI result, witness characteristics and decision delay). All CT/MRI interpretations were performed by independent radiologists. Data were anonymized, coded (HY1, HY2…), and entered daily into SPSS by a research assistant.

Missing or ambiguous time data were clarified during interviews; incomplete CPSS items were excluded. Bias was minimized through consecutive sampling, standardized training, blinding procedures, and a controlled interview environment.

The study follows STROBE guidelines.

Study definitions This section outlines the key terms and operational definitions used throughout the study.

Witness or bystander: Defined as the individual who was with the patient at symptom onset, discovered the patient, or was contacted by the patient.

Onset-to-door time: Defined as the interval from the onset of the patient's symptoms to arrival at the emergency department. Onset-to-door time (ODT) consists of the recognition-to-action time (RAT), determined by the patient experiencing the event or by the stroke witness, and the call-to-door time (CDT), determined by emergency medical services teams. [ODT = RAT + CDT].

Recognition-to-action time: The secondary objectives of this study focus on the recognition-to-action time as determined by the stroke witness. During this interval, the witness undergoes several sequential decision-making processes. Recognizing the suspected stroke symptom(s) constitutes the first decision mechanism; assessing the seriousness of the situation represents the second; inferring whether the condition may be a stroke is the third; deciding whether to call an ambulance or transport the patient to the emergency department is the fourth; and finally, initiating the act of calling EMS-transitioning from decision to behavior-represents the combined decision and action mechanism.

Because, in practice, it is difficult to draw sharp boundaries among these sequential, decision-driven intervals, the time between recognition and taking action was evaluated as a single combined measure in this study. Witnesses were first asked to report the time at which they initially noticed the symptoms, and then the time at which they took action to call an EMS ambulance or transport the patient to the emergency department. The difference between these two time points was defined as the recognition-to-action time.

Delay: In this study, the term prehospital delay (PD) is used to describe delays occurring within the onset-to-door period. Delays within this recognition-to-action interval were referred to as decision delay (DD). The term transfer delay (TD) is used to describe delays occurring within the call-to-door interval. [PD = DD + TD].

Primary CPSS score: Defined as the score obtained directly from the healthcare professional or the layperson (patient or witness), who independently observes the patient's facial droop, arm weakness, and speech using the scale.

Secondary CPSS score: Defined as the score indirectly derived from witness reports by an emergency physician who was blinded to the patient's physical examination and relied on the observations of individuals who witnessed the patient's initial symptoms.