PoCUS Impact on the Diagnostic Approach for Thoracic and Abdominal Pain in the ED

1. Background

Point-of-care ultrasound (PoCUS) is increasingly utilized across various medical and paramedical fields. As a fundamental component of clinical evaluation alongside inspection, palpation, percussion, and auscultation, PoCUS has become indispensable in daily clinical practice enhancing differential diagnosis. In a position statement published in 2015, the American Academy of Emergency Medicine followed by the European Federation of Societies for Ultrasound in Medicine and Biology in 2016 recommended the inclusion of PoCUS in the curricula of medical schools to improve core concepts learning and enhance students' understanding of physical examinations. The integration of PoCUS into clinical practice emphasizes its role in refining the diagnostic approach rather than merely focusing on its diagnostic accuracy.

In daily practice, thoracic pain accounts for about 5% and abdominal pain for 7% to 10% of emergency department consultations. PoCUS can be used in many ways during thoraco-abdominal physical examinations, and most scientific societies encourage its use to address a specific clinical question rather than to provide a diagnosis. For this reason, it is important to focus on the impact of PoCUS on the overall diagnostic approach rather than solely on its diagnostic accuracy. The diagnostic approach includes selecting diagnoses for differential diagnosis, choosing appropriate treatments, and determining necessary complementary examinations, all conducted following the clinical examination.

The primary objective of this study is to evaluate the contribution of PoCUS to the diagnostic approach of patients presenting to the emergency department with thoracic or abdominal pain. Secondary outcomes include the influence of PoCUS on the selection and number of diagnoses in the differential diagnosis, the number of additional treatments or complementary diagnostic examinations, its impact on physicians' confidence in their diagnostic approach, the influence of patient characteristics or PoCUS findings on the primary outcome and evaluate financial aspects. 2. Method

• This study is an interventional multicenter international prospective study evaluating the contribution of PoCUS on the diagnostic approach for patients presenting at the emergency department with thoracic or abdominal pain.

The interventional aspect of the study is secondary to the one-month follow-up of patients based on patients' medical files and phone consultation to establish the final diagnosis. However, PoCUS is considered standard of care, as supported by clear guidelines that advocate for its integration into standard medical practice in both Europe and North America.

Thoracic or Abdominal PoCUS will be performed according to an established protocol

Prior to the study launch, all investigators will participate in a 2-hour refresher course on point-of-care ultrasound (PoCUS) of the thorax and abdomen. Each investigator is already familiar with PoCUS and uses it daily in their clinical practice. Investigators are required to hold a certification or a diploma in PoCUS. They will all be required to rate their comfort level with PoCUS on a Likert scale from 0 to 5, in response to the questions: "On a scale from 0 to 5, how comfortable are you with using PoCUS to evaluate the thorax?" and "On a scale from 0 to 5, how comfortable are you with using PoCUS to evaluate the abdomen?". The investigator will be selected if the comfort level is at 4 or 5.

Patient eligibility will be determined by nurses at triage.

Any patient presenting with thoracic or abdominal pain will be evaluated according to the following three questions: * Can you show me with your hand where is the pain located? * Have you been in pain for less than 72 hours? * Did you undergo any complementary medical examinations to evaluate the pain before coming to our emergency department? If the patient localizes the pain in the anterior thorax or the abdomen, has experienced pain for less than 72 hours, and did not undergo any complementary medical examinations, the triage nurse will call the study investigator. The triage nurse will then continue the triage process with no interference from the study investigator, give painkillers if required, and orientate the patient to the appropriate emergency department sector for medical consultation.

Inclusion process Without interfering with the patient triage, the study investigator will assess the patient's eligibility, explain the study, and obtain a signed informed consent. The investigator will then verify the inclusion, non-inclusion and exclusion criteria and initiate the study process by taking charge of the patient and performing an anamnesis and clinical examination.

The investigator will fill in the first part of the computerized CRF. After validation, no changes can be made by the investigator.

Intervention process The investigator uses PoCUS. The investigator will fill in the second part of the computerized CRF. After validation, no changes can be made by the investigator.

The investigator will then complete the third part of the computerized CRF comprising the PoCUS results.

The investigator is not required to limit the PoCUS examination to the PoCUS protocol if the patient's care requires further PoCUS examinations. However, the rest of the PoCUS examination will be performed after the three sections of the CRF are completed and sealed.

The investigator reports the anamnesis, clinical examination, and PoCUS results in the patient's medical file.

PoCUS images are recorded according to the procedures of the study centers and the capacities of the ultrasound machines.

Evaluation process The first adjudication committee (2 members) will determine the final diagnosis based on the patient's medical records and a follow-up phone consultation conducted at 1-month follow-up. They have no access to the study data except for question relating to the 1-month follow-up.

After validating the final diagnosis and anonymizing the data, the second adjudication committee (3 members) will independently evaluate the diagnostic approaches. This second adjudication committee is blind to the intervention but aware of final diagnosis. Before assessing the diagnostic approaches, CRFs are anonymized and randomly ordered using the "Randomizer for Clinical Trial Lite" Medsharing, Fontenay-Sous-Bois, France. For each included patient, only the study coordinator is aware of the order of the diagnoses approaches (one before and one after PoCUS). The members of the adjudication committee are therefore not aware of which diagnostic approach is before or which is after PoCUS.

After assessing the two diagnostic approaches, two members of the second adjudication committee will determine which diagnostic approach is superior or if the two approaches are equivalent. The third member oversees the adjudication in case of discrepancies.

Study members * Patients Patient eligibility as well as the inclusion, non-inclusion and exclusion criteria are reported above. During the entire study, patients have the right to stop participating. * Triage nurses Triage nurses notify the investigator from the triage section of the emergency department. They do not play a specific role in the study inclusion process. The study inclusion process cannot interfere with the triage. * Investigators The investigators are all emergency physicians who are familiar with PoCUS of the thorax or of the abdomen and who underwent a 2-hour refresher course on the PoCUS process used for this particular study. * Adjudication committee members

* Adjudication committee 1 Two emergency physicians confirm the final diagnoses of patients according to their medical file and a phone consultation at 1-month follow-up. The two physicians work together to determine the correct final diagnosis that explains the pain that led to the emergency department consultation. A third member may be required to adjudicate any discrepancies. * Adjudication committee 2 Two emergency physicians who are blind to the study intervention independently choose the better diagnostic approach according to final diagnosis and a third one adjudicate in case of discrepancy. If no diagnostic approach is considered better, the diagnostic approaches are considered equivalent.

The diagnostic approach will be considered superior if the differential diagnosis, treatment choices and complementary investigations planned are deemed more accurate considering the final diagnosis.

• Research associate Research associates will oversee the 1-month follow-up of patients and will help with the study coordination and launch at the different study centers.

• Biostatisticians Through the "Support en Methodologie et Calculs Statistiques" of the Université Catholique de Louvain, a biostatistician will perform the statistical analyses of this study.

f. Sample size

A total of 369 (323) patients are needed to show a 60% (70%) improvement in the diagnostic approach with a power of 0.8 and an alpha value of 0.05. Considering an attrition rate of 10%, the sample size needed to perform this study is 406 (356) patients. An 60% improvement in the diagnostic approach is based on previous publications showing a 45% to 82% rate of diagnostic improvement after PoCUS use in non-traumatic abdominal pain.

g. Statistical method

The software IBM SPSS statistics 26.0 (SPSS Inc., Chicago, IL, USA) will be used to analyze the data. Continuous variables describing the study population will be detailed using medians, standard deviations, and minimum and maximum values. Discrete variables will be reported by category as numbers and percentages. The χ² test of independence will be used for comparison between discrete variables. The Wilcoxon-Mann-Whitney test will be used for comparison between continuous variables. The significance level corresponds to a p-value of 0.05 or less. The 95% confidence intervals will be calculated using the mid-p exact value.

Primary endpoint

• Assessing the improvement of the diagnostic approach using PoCUS as part of the clinical examination for patients presenting at the emergency department with thoracic or abdominal pain

o This will be evaluated using a proportion test performed according to the expected percentage of improvement (60%).

Secondary endpoints * PoCUS influence on the number of diagnoses in the differential diagnosis, on the number of treatments and on the number of complementary examination(s)

o Comparison of means, paired t-test if parametric data distribution, and Wilcoxon test for non-parametric data distribution * PoCUS influence on the physicians' coefficient of certainty regarding the diagnostic approach

o χ² test * PoCUS influence on the physicians' coefficient of certainty regarding the final diagnosis if this diagnosis is part of the differential diagnosis established bedside

o χ² test * PoCUS usefulness evaluated by the physician in charge (not useful, useful, very useful)

o χ² test * Influence of PoCUS findings on the primary outcome (Positive PoCUS or negative PoCUS)

o Proportion test * Influence of patients' characteristics (BMI, echogenicity, triage score, pain scale, final diagnosis) on the primary outcome

* Proportion test * χ² test to evaluate the categories established in the subgroups compared to each other * Influence of PoCUS on financial aspects

* Proportion test * χ² test to evaluate the categories established in the subgroups compared to each other 3. Data management

• PoCUS influence on the number of diagnoses in the differential diagnosis, on the number of treatments and on the number of complementary examination(s) [Time frame: From enrollment to the completion of the one-month follow-up]
• PoCUS influence on the physicians' coefficient of certainty regarding the diagnostic approach [Time frame: From enrollment to the completion of the one-month follow-up]
• PoCUS influence on the physicians' coefficient of certainty regarding the final diagnosis if this diagnosis is part of the differential diagnosis established bedside [Time frame: From enrollment to the completion of the one-month follow-up]
• PoCUS usefulness evaluated by the physician in charge [Time frame: From enrollment to the completion of the one-month follow-up]
• Influence of PoCUS findings on the primary outcome (Positive PoCUS or negative PoCUS) [Time frame: From enrollment to the completion of the one-month follow-up]
• Impact of the body mass index level on the primary outcome [Time frame: From enrollment to the completion of the one-month follow-up]
• Influence of PoCUS on financial aspects [Time frame: From enrollment to the completion of the one-month follow-up]