Quantification of carotid stenosis on CT angiography--does gender matter?

Does Gender Matter? I read with interest the report by Bartlett et al describing a linear relationship between millimeter carotid stenosis, as measured on CT angiography, and derived percent stenosis. According to the “Materials and Methods” section, the authors did not evaluate their patient population on the basis of sex. Tartaglino et al, however, reported that men and women differ in the average size of their internal carotid arteries (ICAs) on CT angiography by a minimum of 10% (larger in men). It is interesting to note that average brain weight is also approximately 10% greater in men than women. Bartlett et al reported an average distal ICA diameter of 4.4 mm. If their study population included equal numbers of men and women, it is plausible that the average distal ICA diameter would have been 4.6 mm in men and 4.2 mm in women. A 1.3-mm residual lumen in a female patient with a distal ICA diameter of 4.2 cm yields a 69% stenosis. Moreover, some women would likely have even smaller distal ICA diameters, resulting in a degree of stenosis 69%. Tartaglino et al found that the 70% stenosis threshold by North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria required a smaller residual diameter for women than for men. In summary, there is a potential effect of sex on the authors’ measurement of 1.3 mm as a threshold value for assigning stenosis 70% by NASCET criteria. Although the potential effect is subtle, assigning separate threshold measurements for men and women (even if these differed by only 1 mm) might have further strengthened the authors’ conclusions.