The halo sign: HRCT findings in 85 patients

The halo sign consists of an area of ground-glass opacity surrounding pulmonary lesions on chest CT scans. We compared immunocompetent and immunosuppressed patients in terms of halo sign features and sought to identify those of greatest diagnostic value.This was a retrospective study of CT scans performed at any of seven centers between January of 2011 and May of 2015. Patients were classified according to their immune status. 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.Of the 85 patients evaluated, 53 were immunocompetent and 32 were immunosuppressed. Of the 53 immunocompetent patients, 34 (64%) were diagnosed with primary neoplasm. Of the 32 immunosuppressed patients, 25 (78%) were diagnosed with aspergillosis. Multiple and randomly distributed lesions were more common in the immunosuppressed patients than in the immunocompetent patients (p u003c 0.001 for both). Halo thickness was found to be greater in the immunosuppressed patients (p u003c 0.05).Etiologies of the halo sign differ markedly between immunocompetent and immunosuppressed patients. Although thicker halos are more likely to occur in patients with infectious diseases, the number and distribution of lesions should also be taken into account when evaluating patients presenting with the halo sign.O sinal do halo consiste em uma area de opacidade em vidro fosco ao redor de lesoes pulmonares em imagens de TC de torax. Pacientes imunocompetentes e imunodeprimidos foram comparados quanto a caracteristicas do sinal do halo a fim de identificar as de maior valor diagnostico.Estudo retrospectivo de tomografias realizadas em sete centros entre janeiro de 2011 e maio de 2015. Os pacientes foram classificados de acordo com seu estado imunologico. Dois radiologistas toracicos analisaram os exames a fim de determinar o numero de lesoes e sua distribuicao, tamanho e contorno, bem como a espessura do halo e quaisquer outros achados associados.Dos 85 pacientes avaliados, 53 eram imunocompetentes e 32 eram imunodeprimidos. Dos 53 pacientes imunocompetentes, 34 (64%) receberam diagnostico de neoplasia primaria. Dos 32 pacientes imunodeprimidos, 25 (78%) receberam diagnostico de aspergilose. Lesoes multiplas e distribuidas aleatoriamente foram mais comuns nos imunodeprimidos do que nos imunocompetentes (p u003c 0,001 para ambas). A espessura do halo foi maior nos imunodeprimidos (p u003c 0,05).As etiologias do sinal do halo em pacientes imunocompetentes sao bastante diferentes das observadas em pacientes imunodeprimidos. Embora halos mais espessos ocorram mais provavelmente em pacientes com doencas infecciosas, o numero e a distribuicao das lesoes tambem devem ser levados em conta na avaliacao de pacientes que apresentem o sinal do halo.