Commentary on “Abdominal Aortic Aneurysms with High Thrombus Signal Intensity on Magnetic Resonance Imaging Are Associated with High Growth.” The Devil is in the Detail

Abstract

Has it never happened to you that a good intention ended up being harmful? Nguyen et al. have demonstrated the association between the intensity on magnetic resonance imaging (MRI) and intra-aneurysm thrombus and abdominal aorta aneurysm (AAA) growth rate. Their finding is interesting as it keeps pushing forward the knowledge of aneurysm disease. Many others have tried to figure out the risk markers of AAA growth/ rupture. The scope, magnitude, multicity, and spread of such potential studied markers is highly varied. So far, a method for predicting AAA growth and rupture remains elusive, and a reliable parameter to identify those patients who will benefit from early AAA repair is lacking. We completely agree with the Maastricht group when they state that an ideal marker should have a causal relationship to the relevant disease, be involved in all the pathophysiological pathways, and reflect disease severity and progression by its measurement, or all three. Furthermore, the biomarker should be sensitive to intervention. The group claims, and we agree, that the validation of such markers should rely on the basic principles of biological plausibility, correlation with epidemiological studies, and clinical relevance and treatment effects on the biomarker. However, none of the candidates (including the last one, the high thrombus signal intensity from Nguyen) has yet met the triad of marker/surrogate criteria. It is not possible, so far, to use them as an AAA diagnostic tool. The first requirement is that candidates have a conclusive statistical association with the expansion rate. Furthermore, they must prove a linear correlation. It must be said that in no case do the candidates meet this condition. Any mathematical inconsistency, disparity of data between different publications, suspicion of bias (i.e. selection bias due to small sample size), and any weak correlation invalidate such factors as reliable and individual predictors of AAA progression. Such details as the sample representativeness (i.e. inconsistencies in the expected relationship between cross-