The present study highlights the prognostic role of the first chest CT during hospitalization in patients with COVID-19. The CT quantitative score has a vital role in predicting the outcome of those with confirmed COVID-19. This prognostic role of the first chest CT appears to be stronger than that of age, sex, BMI, hs-CRP, hypertension, and pre-renal azotemia. The discriminatory feature of our patients was that they all had a history of CAD. The study endpoint, a composite of death and ARDS requiring mechanical ventilation, occurred in 17 (35.45%) patients. The relationship between the CT score and the outcome had a large effect size (0.634) compared with that for BMI (0.284), hs-CRP (0.327), and hypertension (0.245), suggesting that the score of the first chest CT had a strong correlation with the worse outcome in comparison with the other factors.
For the diagnosis of COVID-19, Ai et al. [13] reported positive rates of 59% for rRT-PCR and 88% for chest CT imaging, with chest CT having a sensitivity of 97%. The authors also reported that 60 to 93% of their patients had initial lung involvement in chest CT even before the initial positive rRT-PCR results, although 75% of their patients with negative rRT-PCR tests had positive chest CT findings. Ai and colleagues considered 48% of these patients to be highly likely cases and 33% probable cases [13]. Consequently, chest CT has a high sensitivity for the diagnosis of COVID-19. It has also been suggested that chest CT can be regarded as a primary modality for COVID-19 detection, especially in epidemic areas [14].
Pan et al. [10] reported their chest CT scores in 4 stages: 2 ± 2 (0–6) in the early stage (0–4 days), 6 ± 4 in the progressive stage (5–8 days), 7 ± 4 in the peak stage (9–13 days), and 6 ± 4 in the absorption stage (≥ 14 days after the onset of symptoms), which is similar to our findings given the time interval from symptoms. Lung involvement is more severe 6 to 11 days (approximately on day 10) after the initiation of symptoms [6, 13]
Li et al. [8] concluded that a CT severity score with a cutoff of 7.5 was able to diagnose severe pneumonia with 100% specificity and 82.6% sensitivity. In the present study, our data showed a cutoff of 2.5 with a sensitivity of 76.5% and a specificity of 77.4%. Our literature review demonstrated that the sensitivity of chest CT for the diagnosis of COVID-19 ranges from 44 to 98% [6, 13,14,15,16], which may be because of various time durations from symptom onset to the first chest CT. For instance, the results of a study by Wang et al. [6] indicated that the sensitivity of chest CT for COVID-19 increased over time after symptom onset to 84% (95% CI 73 to 92%) and 99% (95% CI 93 to 100%) for disease days 0 to 5 and 6 to 11, respectively. In our research, the median time interval between the presentation of symptoms and chest CT was 3 days (range = 0–9 days), which may be due to the fact that most patients present to medical centers with a delay of several days following the prodromal symptoms of COVID-19. Even though in our study, the first CT scan was performed in the early days after the onset of symptoms (75% before day 5 of the disease), the results indicated the significant independent value of the first CT score in predicting in-hospital outcomes. It appears that the first CT can be considered an independent predictive factor for death and mechanical ventilation in patients with concomitant CAD and COVID-19 infection.
The risk factors of a poor prognosis in patients with COVID-19 include old age (≥ 50 years); male sex; smoking; chronic kidney disease; chronic obstructive pulmonary disease; cerebrovascular disease; elevated levels of lactate dehydrogenase, CRP, and D-dimer; decreased blood platelet and lymphocyte counts; cardiovascular disease; hypertension; and diabetes mellitus [17]. Having at least one comorbidity such as hypertension, diabetes mellitus, cardiovascular disease, and lung disease is a predictive risk factor of progression to severe disease [18]. Nevertheless, in the current study, patients with diabetes mellitus had a lower chance of having the worse outcome than those without the disease (effect size = 0.317). This observation is in line with the recent findings showing that mechanisms employed by anti-diabetic drugs such as metformin and gliptins may be protective against severe infection. It has been hypothesized that target receptors of medications commonly used to treat DM may be involved in the viral entry mechanism of SARS-CoV-2 [19]. However, further studies are required to confirm these observations.
Furthermore, elevated serum levels of CRP, erythrocyte sedimentation rates, and lactate dehydrogenase, as well as high fever, are associated with the severity of lung involvement on initial CT [4]. Obesity is also deemed an independent risk and prognostic factor for the disease severity and the need for advanced medical care in COVID-19 [20]. It can, therefore, be concluded that the value of the severity of lung involvement on admission chest CT in the context of cardiovascular disease is more robust than that of obesity. The first chest CT during workup for COVID-19 should be accorded more significance.
Limitations
The major limitation of the present study is its small sample size, which mostly resulted in wide SDs or wide 95% CIs and precluded us from showing statistically significant differences. To overcome this limitation and evaluate the strength of each statistical claim, we calculated effect sizes to make the correlation between each variable and the outcome comparable with one another. However, a future longitudinal study with follow-up CT results would be of value.
