This prospective analytical study was conducted in COVID-19 isolation unit, Zagazig University Hospitals, Egypt in the period from 1st to end of April 2021. The approval of this prospective study was obtained from the institutional review board and written consents from all subjects were achieved (Figs. 1 and 2).
The inclusion criteria were adult patients (18 years old or more), confirmed to have COVID-19 infection by PCR testing, patients who underwent chest CT scan, and measurements of capillary oxygen saturation using pulse oximetry at the time of admission, and having written informed consent to participate in the research (Figs. 3 and 4).
The exclusion criteria were patients less than 18 years old, patients not confirmed to have COVID-19 infection by PCR testing, patients who did not undergo chest CT scan, patients with unavailable clinical and laboratory data, congenital lung and heart anomalies, and patients with severe hemoglobinopathy or anemia (Figs. 5, 6 and 7).
In this study, the relationship between on-admission chest CT severity score, capillary blood oxygen saturation level, and laboratory inflammatory markers results in adult positive PCR patients with SARS-COV-2 pneumonia was investigated.
All subjects underwent chest CT scan by 128 multi detectors device (Ingenuity Phillips health care), scanning parameters were as follows: scan orientation (craniocaudally), tube voltage (120 kV), tube current (100–600 mA)-smart mA dose modulation, slice collimation (128 × 0.625 mm), width (0.625 × 0.625 mm) and were in supine and deep inspiration. After that, the CT scan images were reassembled.
Two competent radiologists assessed all patients' chest CT scans at the same time and calculated the chest CT severity score for patients (a competent radiologist is a radiologist who has more than 5 years of experience in the field of thoracic imaging). In cases of disagreement, they enlisted the expertise of a third radiologist with more experience in thoracic imaging (more than 8 years).
All pulmonary lobe segments were investigated for the existence and spread of parenchymal abnormalities, like ground-glass opacities, consolidation, crazy paving and pulmonary nodules. Chest CT severity score was assigned for each lobe as follow: 0 for no involvement, 1 for < 5% involvement, 2 for 5–25% involvement, 3 for 25–50% involvement, 4 for 50–75% involvement, and 5 for > 75% involvement. The overall severity score got by summation of scores from all five lung lobes. A mild grade is of 0–7 points, a moderate grade is of 8–16 points, and a severe grade is of 17–25 points.
The sum of points in each lobe was used to calculate the final score, which was used to calculate the CT severity score.
The capillary blood oxygen saturation of all patients was measured and acquired using pulse oximetry. It should also be mentioned that the time interval between performing pulse oximetry and chest CT scan was no more than 1 day because of possible lung and blood oxygen saturation changes with time.
Other clinical information and laboratory results like absolute lymphocyte count, CRP, D-dimer and ferritin levels were also gathered from documents of all patients.
Eventually, 305 patients were included with the following data been collected: age, gender, presence of comorbidities/risk factors, blood oxygen saturation, laboratory results including absolute lymphocyte count, CRP, D-dimer and ferritin levels.
After data collection, it was analyzed to investigate the relationship between chest CT severity score with patient’s capillary blood oxygen saturation values and laboratory inflammatory markers results using IBM SPSS 23.0 for windows. Quantitative data were expressed as mean ± standard deviation (SD). Qualitative data were presented as frequency and percentage.
The following tests were done:
T-test of significance was used when comparing between two means of normally distributed data.
Mann Whitney U test was used when comparing two means of not normally distributed data.
Chi-square (X2) test of significance was used in order to compare proportions between two qualitative parameters.
Pearson`s correlation test was used for comparing two continuous quantitative data. Probability (P value): P value ≤ 0.05 was considered significant, P value ≤ 0.001 was considered as highly significant and P value > 0.05 was considered insignificant.