AB1095 DIAGNOSTIC PERFORMANCE OF THE AORTIC WALL THICKENING DETERMINED BY ROUTINE CT-SCAN FOR THE DIAGNOSIS OF AORTITIS OVER 50 YEARS OF AGE

Background:

Making the diagnosis of aortitis may be challenging in the “real life”.18F-FDG PET/CT (PET) has emerged has the gold standard to diagnose aortitis but it is expensive and not always quickly available. Injected CT-scan (CT) can also be used to diagnose aortitis, which is suspected when there is an extended circumferential, non-atherosclerotic increase of the aortic wall thickness (AWT). However, data are lacking on the diagnostic performances of AWT to diagnose aortitis.

Objectives:

To describe the diagnostic performance of AWT measured by CT to diagnose aortitis in patients over 50 years of age.

Methods:

We performed a monocentric retrospective study between 2013 and 2018 including 1) all patients over 50 years of age who had performed a PET for inflammation or fever of unknown origin or for suspicion of classical giant cell arteritis (GCA), aortitis or large vessel vasculitis (LVV); 2) with an injected CT-scan performed in the 30 days before or after PET; 3) not diagnosed to have cancer or infection 4) exposed to corticosteroids for less than 3 days at the time of CT and PET. The gold standard for aortitis was PET positivity according to the 2018 European consensus grading criteria (1). AWT was measured at different aortic segments (ascending aorta, descending thoracic aorta and suprarenal abdominal aorta) by a single radiologist unaware of the result of PET and of the previous interpretation of CT-scan.

Results:

Eighty-nine patients were included (female: 47%; mean age 68.8 (50-93) years; GCA: n=28). Twenty patients had aortitis according to the PET result (GCA: n=16).

Mean maximal aortic wall thickening was: 3.25 mm (median: 3.3; range: 2-4.6) in the aortitis group and 2.2 mm (median: 2.1; range 1-3.8) in the negative PET group (p < 0.001).

The best ROC curve AUC (85%) was obtained considering the maximal AWT on the thoracic and suprarenal abdominal aorta only. The AUC of the ROC curve at the ascendant thoracic aorta was poor (75%) (Figure).

The Youden’s index of the ROC curve was 2.6 mm with a sensitivity of 85 % and specificity of 71 % (Table) for aortitis diagnosis. An AWT ≤ 2.0 mm exclude the diagnosis of aortitis. The 3 mm threshold had a PPV of only 52% and an AWT ≥ 4 mm was fully specific.

Conclusion:

Aortitis diagnosis using a routine injected CT-scan interpreted by a single radiologist may be certain when showing an AWT ≥ 4 and excluded for an AWT≤ 2.0. The threshold of 3 mm seems not sufficiently specific to diagnose aortitis without a confirmatory PET.

References:

[1]Riemer H.J.A. Slart et al. FDG-PET/CT(A) imaging in large vessel vasculitis and polymyalgia rheumatica: joint procedural recommendation of the EANM, SNMMI, and the PET Interest Group (PIG), and endorsed by the ASNC. Eur J Nucl Med Mol Imaging. 2018 Jul;45(7):1250–69.

Table.

Performance of different threshold for maximal thickness of the aortic wall for diagnosis of aortitis using PET positivity as the gold standard*.

Thickness (mm)SensitivitySpecificityNPVPPVaccuracy≥ 1.9100 %30.4%100 %29.41 %46 %≥ 2.0100 %31.88 %100 %29.85 %47 %≥ 2.295 %53.62 %97.36 %37.25 %63 %≥ 2.685 %71.01 %94.23 %45.94 %74 %≥ 3.060 %84.05 %87.88 %52.17 %78 %≥ 3.360 %92.75 %88.89 %70.59 %85 %≥ 3.535 %95.65 %83.54 %70 %82 %≥ 3.825 %98.55 %81.92 %83.33 %82 %≥ 4.020 %100 %81.17 %100 %82 %

*Made with ROC curve in descendant thoracic and suprarenal segment of the aorta; PET:18F-FDG PET/CT; NPV: negative predictive value; PPV: positive predictive value.

Figure.

ROC curve of aortic wall thickness, in descendant thoracic and suprarenal abdominal segments for the diagnosis of aortitis.

Disclosure of Interests:

None declared

Emergence of murine typhus in La Réunion, France, 2012-2017

OBJECTIVE

Murine typhus (MT) is an acute zoonosis caused by Rickettsia typhi, a flea-borne rickettsiosis. The first autochthonous case was reported in 2012. Once autochthonous transmission of Rickettsia typhi was proven, we performed a prospective study to describe and raise awareness of this often-misdiagnosed disease among physicians.

PATIENTS AND METHODS

We performed a prospective observational study of MT cases in La Réunion from 2012 to 2017. MT cases were defined as clinically compatible illnesses with a specific positive serology and/or PCR.

RESULTS

Sixty-one confirmed cases were collected. The main clinical features were prolonged fever (90%), asthenia (87%), and headaches (79%). The main biological abnormalities were elevated liver enzymes (84%) and thrombopenia (75%). Renal function was normal in 90% of cases; it was an important feature because leptospirosis is a frequent cause of acute renal failure. A seasonal factor was observed with 79% of cases reported in the warm season and most of them in the west and south of the island (i.e., the dry areas).

CONCLUSION

MT is an emerging disease in La Réunion, and local conditions could lead to an endemic situation. Cases of acute undifferentiated fever with headaches should guide to the diagnosis of MT especially in the warm season and dry areas. Leptospirosis is an alternative diagnosis, which differs from MT by its epidemiological characteristics and by the associated frequent renal dysfunction.