Techniques for measuring regional body fat: computed tomography may be suitable for evaluation of facial lipoatrophy

Abstract

We read with interest the report by Martinez et al. [1] about the potential role of sonography as a tool to quantify regional fat in HIV-infected patients. The authors stated that ‘concerning facial lipoatrophy, only sonography and three-dimensional surface laser imaging have been used to assess facial lipoatrophy’. They do not mention that computed tomography (CT) may also be suitable to quantitate facial fat. In December 2004 we published our experience evaluating quantitative CT to measure facial fat in 61 consecutive HIV-infected patients receiving antiretroviral therapy [2]. CT was performed on a Xpress/Gx helical scanner (Toshiba Medical Systems Europe, Zoetermeer, the Netherlands). The total right-side facial tissue area (TTA) and the facial adipose tissue area (ATA) were assessed by a single 7 mm slice obtained at the level of the upper lip. The ATA: TTA ratio was automatically calculated. The facial area was measured by drawing a line, which delineates the skin surface and continues on the external surface of the maxilla, ascending ramus of the mandible and posterior surface of parotid gland [2]. Patients with facial lipoatrophy had less malar skinfold, less facial ATA and less facial ATA: TTA ratio compared with patients without facial wasting. Moreover, a gradation in the measurements obtained by CT in association with the severity of lipoatrophy was found. The values of facial ATA of less than 2.34 cm2 and facial ATA: TTA ratio of less than 0.10 had a sensitivity of 71 and 74%, and a specificity of 71 and 67%, respectively, to diagnose facial fat loss. In our study, inter and intra-observer variability for CT scan measurements were acceptable, with the ATA: TTA ratio showing lower variation than the facial ATA. As Martínez et al. [1] mentioned there is a great need for technology to quantitate facial fat in HIV-infected patients. HIV clinicians and researchers should know that a single-slice CT scan may allow facial fat quantification and may be useful to diagnose and monitor facial lipoatrophy.