Sinal do halo em tomografia computadorizada de tórax : valor diagnóstico em pacientes imunocompetentes e imunocomprometidos

Abstract

Introduction: The halo sign consists of an area of ground-glass opacity surrounding pulmonary lesions on chest computed tomography (CT) scans. Different diseases have already been described as causing this finding, though a larger and more objective analysis of this sign has not been conducted yet. Materials and methods: The authors compared CT images of immunocompetent and immunosuppressed patients in terms of halo sign features and seek to identify those of greatest diagnostic value. An observational study of exams performed between January of 2011 and May of 2015 was carried out. After initial database search with keywords, two thoracic radiologists reviewed the scans in order to determine the number of lesions, as well as their distribution, size, and contour, together with halo thickness and any other associated findings. The study obtained approval by the institutional ethics committee. The chi-squared test, Student t test and Mann-Whitney U test were adopted according to sample characteristics, with a bilateral level of significance of 0.05. Results: A total of 85 patients (46 male, 54%) were evaluated, with 53 (62%) immunocompetent and 32 (38%) immunosuppressed. The main diagnosis among immunocompetents was lung cancer (n=32, 64%), whereas aspergillosis was the main condition in immunosuppressed patients (n=25, 78%). Multiple and randomly distributed lesions were more frequent in the immunosuppressed group (p<0.001), with halo thickness also greater in this group (p<0.05). Conclusions: We concluded that the causes of the halo sign differ significantly according to immune status, and that halo thickness, the number and the distribution of lesions are the data with greatest diagnostic value.