Introduction Sickle cell disease is the most common inherited genetic disorder in France and worldwide. Its main acute manifestation is vaso-occlusive crisis, a frequent reason for emergency department visits. Acute chest syndrome is the leading complication and cause of death during vaso-occlusive crisis, occurring in approximately 15-20% of hospitalized episodes, often within the first few days after symptom onset. Early identification of patients at risk of developing acute chest syndrome remains a major clinical challenge. Although predictive clinical and biological scores exist, their ability to identify high-risk patients remains limited in daily practice. Chest X-ray has traditionally been used to support the diagnosis of acute chest syndrome, but its diagnostic performance and repeated radiation exposure are increasingly questioned. Lung ultrasound is a non-invasive bedside imaging tool that has shown good performance for detecting pleural effusion, alveolar consolidation and interstitial syndrome, and is increasingly used by emergency physicians. However, its diagnostic performance when systematically performed by emergency physicians in adult sickle cell patients presenting with vaso-occlusive crisis has not yet been specifically assessed.
Hypothesis / Objective We hypothesize that systematic pleuropulmonary ultrasound performed early after emergency department admission may help identify patients with vaso-occlusive crisis who are at risk of developing acute chest syndrome, and may allow earlier diagnostic assessment. The primary objective of the ECHODREP study is to evaluate the diagnostic performance of systematic pleuropulmonary ultrasound, performed by an emergency physician within six hours of admission, for the diagnosis of acute chest syndrome during hospitalization in adult sickle cell patients presenting with vaso-occlusive crisis.
Secondary objectives are to assess the association between ultrasound findings and the final diagnosis of acute chest syndrome, to describe patient outcomes according to ultrasound results, including hospitalization, admission to intermediate care, emergency department revisits and mortality at day 3, day 7 and day 28, and to compare ultrasound performance according to the operator's level of experience.
Method ECHODREP is a prospective, observational, single-arm, monocentric diagnostic performance study conducted in the Emergency Department of Henri-Mondor University Hospital. The study will include 200 adult patients with sickle cell disease - SS, SC or S-beta-thalassemia - presenting to the emergency department for vaso-occlusive crisis. Patients with a diagnosis of acute chest syndrome already established on arrival, patients previously included in the study, protected adults, and patients refusing participation will not be included.
After informed consent, a pleuropulmonary ultrasound will be performed within six hours of emergency department admission by an emergency physician investigator who is not involved in the patient's clinical care. The examination will assess twelve predefined lung zones. In order to avoid influencing standard care and to preserve the objectivity of the study, ultrasound findings obtained for research purposes will not be communicated to the treating medical team and will not be used for diagnostic or therapeutic decisions.
Patients will receive standard care for vaso-occlusive crisis according to local practice. A telephone follow-up will be performed at day 28 to collect vital status, emergency department revisits, hospitalizations and any secondary diagnosis of acute chest syndrome. At the end of follow-up, an independent adjudication committee, blinded to the research ultrasound findings, will determine the final diagnosis: uncomplicated vaso-occlusive crisis or acute chest syndrome.
The primary endpoint will be the diagnosis of acute chest syndrome within seven days after emergency department admission or before hospital discharge, based on the medical record. Diagnostic performance will be assessed by calculating sensitivity, specificity, positive and negative predictive values, likelihood ratios and area under the ROC curve, with 95% confidence intervals. Additional analyses will compare outcomes according to ultrasound findings and operator experience.
Conclusion This exploratory study will provide original data on the diagnostic performance of early pleuropulmonary ultrasound performed by emergency physicians in adult sickle cell patients presenting with vaso-occlusive crisis. If ultrasound demonstrates adequate diagnostic accuracy, it could contribute to earlier identification of acute chest syndrome, improve risk stratification in the emergency department and help optimize the management pathway of these patients. By evaluating both diagnostic performance and patient outcomes, ECHODREP may support the integration of lung ultrasound into future diagnostic strategies for acute chest syndrome in sickle cell disease.
