This retrospective study was conducted on 574 patients who were diagnosed as COVID-19 and confirmed by real-time polymerase chain reaction (RT-PCR) during the period from 1 April 2020 to 1 July 2020, and no exclusion criteria were applied.
These selected patients were classified according to their age into six groups: (group A) less than 30 years, (B) from 31 to 39 years, (C) from 40 to 49 years, (D) 50–59 years, (E) from 60 to 69 years, and (F) 70 years and more.
The study was carried out after obtaining the permission of the Ethics Committee of Scientific Research, Faculty of Medicine, and as the study had no risk and does not affect the patients’ rights, the informed consent was waived.
All patients underwent non-contrast multi-slice computed tomography (MSCT) chest for evaluating the severity of the disease in different age groups.
All patients underwent chest CT examination without intravenous contrast in a supine position; CT images were acquired in the caudo-cranial direction from the level of diaphragm to lung apices, using 64-channel multi-detector CT scanner (Toshiba, Japan) Aquilion machine with 120–140 kV, 16 × 1.2 mm collimation, and tube current 150–280 mA; all transverse images were reconstructed to 0.625 mm-slice images.
CT chest image interpretation
Images were transferred to a Vitrea Vital Image (VPMC-Revision C) and multi-planar reconstruction (MPR) was used for image analysis.
CT images were reviewed by two radiologists with more than 10 years’ experience in imaging.
For each patient, a CT scan was evaluated for the following:
Lesion density: ground glass, mixed ground glass with consolidation, or only consolidation.
Lesion distribution: peripheral (sub-pleural, involve peripheral one-third of the lung), central (at lung hilum, involve central two-thirds of the lung), or diffuse.
Other signs: such as air bronchogram, pulmonary nodules, cavitation, pleural or pericardial effusion, fibrotic bands, bronchiectasis, or adenopathy.
The number of lobes affected.
Unilateral or bilateral involvement.
Coronavirus disease imaging reporting system (COVID-RADS) classification was also applied for each patient based on CT findings . This is summarized in Table 1.
Also, the CT severity score was calculated by division of both lungs into five lung zones (right upper lobe, right middle lobe, right lower lobe, left upper lobe (including lingula), and left lower lobe) as regard anatomical structures.
A score was given for each lung lobe based on the percentage of lobe involvement:
Score 0: 0% involvement
Score 1: less than 5% involvement
Score 2: 5% to less than 25% involvement
Score 3: 25% to less than 50% involvement
Score 4: 50% to less than 75% involvement
Score 5: 75% or greater involvement
The maximum CT score for both lungs is 25, and the summation of both lung scores provides a semi-quantitative evaluation of the total severity score.
Then, according to the percentage of whole lung involvement, the grade of disease severity was classified into:
Finally, the total severity score and grading were calculated for each patient, and correlation with age in both sexes was done.
Data was collected and analyzed using SPSS (Statistical Package for the Social Science, version 20, IBM, and Armonk, New York). Continuous data were expressed in form of mean ± SD or median (range) while nominal data were expressed in form of frequency (percentage).
The normality test for the age and total lung score was performed by the Shapiro test where it was significant. Hence, age and lung scores were not normally distributed data. Chi2 test was used to compare nominal data in the study while continuous data were compared either by Mann–Whitney U test (in case of two different groups) or Kruskal–Wallis test (in case of more than two different groups).
Spearman rank correlation was used to determine correlation between age and total lung score (mild correlation if r = 0.20–0.40, moderate correlation if r = 0.40–0.60, strong correlation if r = 0.60–0.90, and perfect correlation if r = 1). Level of confidence was kept at 95% and hence, P value was considered significant if < 0.05.