Performance and costs of rule-out protocols for acute aortic syndromes: analysis of pooled prospective cohorts

Background: Acute aortic syndromes (AAS) are deadly conditions causing unspecific symptoms, such as chest/abdominal/back pain, syncope and neurological deficit. They are diagnosed with computed tomography angiography (CTA), but the patient selection is challenging. To support physicians and standardize management, protocols combining a clinical score with D-dimer (DD) have been developed. However, direct comparison of their diagnostic performance and cost-effectiveness is lacking. Methods: We used individual patient data from 3 prospective diagnostic studies of patients with suspected AAS, enrolled in 12 centers from 5 countries. Diagnostic accuracy, failure rate and costs were calculated for 5 protocols, applying 3 scores (aortic dissection detection [ADD], AORTAs and Canadian) and 2 DD thresholds (500 ng/mL [DD500], age-adjusted [DDage]). Costs were estimated using Italian and German reimbursements. Results: Among 4907 patients, 506 (10.3 %) had an AAS. The sensitivity of the diagnostic protocols ranged from 97.6 % for Canadian/DD500 to 99.4 % for AORTAs/DD500 or DDage (P = 0.022). The specificity was lowest for AORTAs/DD500 (46.8 %; P < 0.001 vs AORTAs/DD500) and highest for ADD/DDage (61.5 %; P < 0.001). The number of potential AAS misses was 4-fold higher with Canadian/DD500 vs AORTAs/DD500 or DDage. The net clinical benefit was highest for ADD/DDage. All protocols reduced CTA exams and costs over a CTA-to-all strategy. Numbers of predicted CTA exams and costs per 100 patients were lowest for ADD/DDage (447 CTAs, 34,366 EUR) and highest (579 CTAs, 43,628 EUR) for AORTAs/DD500. Conclusions: Guideline-compliant clinical score/DD based protocols are highly sensitive. Differences in specificity and efficiency are present. Data may guide decision-making based on policies and resources.