The goal of this study is to evaluate the safety of integrating the Aortic Dissection Detection Risk Score (ADD-RS) and D-dimer testing for ruling out acute aortic syndrome (AAS) in the emergency department (ED). The main question it aims to answer: Can the combination of the ADD-RS <2, and D dimer <500ng/mL rule-out AAS in ED patients without CTA? The researchers will recruit patients suspected with AAS in the ED, and the patients will receive a ADD-RS score, a D-dimer testing after signing a written consent.

Inclusion Criteria:

• Adult patients aged ≥ 18 years; AND
• Presentation to the ED with any of the following symptoms: acute onset (<14 days) chest pain, abdominal pain, back pain, syncope, or signs of malperfusion (e.g. limb ischemia, neurological deficit); AND
• AAS is considered as a possible differential diagnosis by the treating physician. Enrolment in the study will be determined by the attending physician during initial medical consultation in the ED and prior to establishing a final diagnosis.

Exclusion Criteria:

• An alternative diagnosis to AAS established by the treating physician after the initial assessment; OR
• Trauma cases; OR
• Patients with a known diagnosis of AAS before the index ED visit (e.g. with a diagnostic imaging done before the ED visit or referral from other institutions for AAS); OR
• Clinical severity or other conditions not allowing complete evaluation/proper enrolment; OR
• Patient who refuse to participate.

Patients presenting to the ED meeting the above criteria during the recruitment timeframe

Data collected from this study is exclusively for our own institutional research purpose.