The Aortic Dissection Detection Risk Score (ADD-RS) and D-dimer
The Diagnostic Challenge
Acute aortic dissection is a rare, yet serious cardiovascular emergency with a broad range of clinical presentations and the potential consequences of a missed diagnosis are grave. CT angiography is the most widely used means of reaching a definitive diagnosis and can diagnose the condition with a high degree of accuracy but carries the risk of radiation and contrast exposure. Consequently, both missed diagnosis, and over-investigation, are key concerns.
How to approach the low-to-moderate risk patient, where an acute aortic dissection is within the pool of differential diagnoses, can be a decision-making quandary for the ED clinician.
ADD-RS
The Aortic Dissection Detection Risk Score (ADD-RS) is a clinical risk stratification tool that can aid decision-making and workup in patients where acute aortic dissection is suspected.
| Clinical Finding | Points | |
|---|---|---|
| Any high-risk condition | – Marfan syndrome – Family history of aortic disease – Known aortic valve disease – Recent aortic manipulation – Known thoracic aortic aneurysm | +1 point |
| Any high-risk pain feature | Chest, back, or abdominal pain described as any of the following: – Abrupt onset – Severe intensity – Ripping/tearing in nature | +1 point |
| Any high-risk exam feature | – Evidence of perfusion deficit (pulse deficit, systolic BP differential, or focal neurological deficit in conjunction with a history of pain) – New murmur of aortic insufficiency (with any history of associated pain) – Hypotension or shock state | +1 point |
Patients are considered low risk if the score is 0, intermediate risk if the score is 1, and high risk if the score is >1. Evidence suggests that around 95% of patients diagnosed with acute aortic dissection are identified as intermediate or high risk using this scoring tool.
D-dimer
D-dimer is typically elevated in patients with acute aortic dissection. Studies have looked at using D-dimer as a screening tool for AAD at a cut-off of 500ng/ml, where a positive D-dimer has been found to be around 96% sensitive for AAD.
A positive D-dimer is, of course, a very non-specific finding. However, a negative D-dimer could make for a useful rule-out test in low-risk patients.
ADD-RS + D-dimer
The ADvISED prospective multicentre study has looked at using the ADD-RS clinical risk stratification tool in combination with D-dimer as a novel clinical pathway for ruling out acute aortic dissection. In this study, using an ADD-RS score of ≤1 and negative D-dimer was 98.8% sensitive for the detection of acute aortic dissection.
The study authors propose the following diagnostic approach:
- For patients with ADD-RS >1, consider proceeding directly to CTA or other conclusive imaging
- For patients with ADD-RS ≤1, consider D-dimer testing. If D-dimer is <500ng/ml, consider stopping workup for aortic dissection and consider alternate diagnoses; if >500ng/ml, consider proceeding to CTA or other conclusive imaging.
Whilst this pathway has not been externally validated, the evidence from this study may be helpful to the ED clinician when it comes to making informed decisions. This kind of approach could help to avoid the need for CT in lower risk patients.