Chest CT-scan scoring
These patients had previously undergone chest CT-scan in the acute phase of the infection. A ”Lung Total Severity Score” (LTSS) done by a radiologist at that time designated the severity of lung infiltration. This scoring which was based on the method introduced by Kunwei Li et al. (9), was calculated by assessing each of the lung lobes and assigning a score to them (from 0 to 4) based upon the percentage of ground-glass opacity or consolidation as follows: 0 (0%), 1 (1-25%), 2 (26-50%), 3 (51-75%), or 4 (76-100%). Then, the sum of all the lobes’ scores gave out the TLSS, which was expected to be a number ranging from 0-20. According to this scoring, we divided the patients into two categories. LTSS=0 delineated no lung involvement, and LTSS≥ 1 was considered to have some extent of lung involvement.