The extent of pneumonia in the SARS patients with longitudinal follow-up is assessed by a radiologist according to a serial chest radiographic score, modified from a score system initially proposed to assess computer tomography of the chest (16) and summarized as in Fig. 2.
Fig. 2. Assessing the extent of pneumonia by chest X-ray opacity score. The opacity in each zone (apex+upper, middle, and lower zones) from the left and right regions of the lung was scored by a “coarse semiquantitative method” with a 5 points’ scale of grades 0–4 representing involved areas of 0, 5–24, 25–49, 50–74, and 75–100%, respectively. A total score was then calculated by adding up all the grades in the six zones (Apex and upper zones were considered as one zone) to provide a 0–24 points’ scale with the higher number representing more severe pneumonic disease.