Chest CT has a high sensitivity for diagnosing COVID-19 [21]. Scientific societies have different recommendations for the employment of imaging in COVID-19 management, with many recommendations against CT’s employment in screening. To enhance the role of imaging and CT chest, structural reporting is established to improve communication between radiologists and clinicians with recommendations to include a RADS system among the declared systems since the start of the global pandemic, among the popular lexicons are CO-RADS and COVID-RADS [21].
Both lexicons were created to categorize the suspicion with COVID-19 affection, whereas the typical CT findings were graded as CO-RADS score 5 and COVID-RADS score 3 with the implication of very high and high suspicion level according to each lexicon, respectively. On the other hand, normal chest CT findings are categorized as CO-RADS score 1 or COVID-RADS score 0, reflecting unlikely occurrence or low suspicion, but both scores are not an exclusion of COVID-19 affection [10, 11].
Moreover, the atypical findings are consistent with COVID-RADS score 1 and CO-RADS score 2, implicating a low level of suspicion in both lexicons. Furthermore, the COVID-RADS lexicon included score 2A that includes fairly atypical findings or score 2B that combines typical/fairly typical and atypical findings, while CO-RADS score 4 includes suspicious abnormalities with a high level of suspicion [10, 11].
CO-RADS score 3 reflects an indeterminate level of suspicion. Such a score is not included in the COVID-RADS lexicon [10, 11].
The CO-RADS lexicon contains grade 0 for technically insufficient studies and grade 6 for positive RT-PCR cases [10]. The latter two grades were not included in our study to facilitate comparison between both lexicons as COVID-RADS does not include opposing categories.
The clinical picture of COVID-19 disease is quite variable [22]. Among our patient cohorts, cough, fever, and diarrhea were the most common presenting symptoms, to the point that some authors considered feco-oral transmission as a potential transmission route [23]. While Menni et al. [24] have reported that loss of taste and smell senses as pathognomonic symptoms, the current study recorded them among the least presenting symptom, this in agreement with Gautier et al. [25].
The majority of cases had a high clinical suspicion index as the study was carried out during the pandemic phase. This may also explain the rush to perform CT imaging in the disease’s early phases [18].
Sultan et al. [26] documented a significant difference in pulmonary CT findings of COVID-19 with the variation in clinical presentation onset duration. Ding et al. [27] defined 6 stages of different durations in the course of the disease. Accordingly, Prokop et al. [10] subjects fell in the second and third groups. In comparison, the current study cohort was categorized in the first two stages.
The early tendency to perform imaging could be explained by the fact that in developing countries, CT imaging may be considered the only available diagnostic modality due to the shortage of laboratory kits facing a spike in patient numbers or even logistic strains; developed countries are not an exclusion from these circumstances [24, 28].
Despite that, Ding et al. [27] reported that disease findings change rapidly at the early stages. However, the current study findings indicated no/minimal correlation was present between symptoms to imaging duration interval versus clinical suspicion index or assessment of both lexicon scores results (CO-RADS or COVID-RADS) or even the preferred score. On the other hand, Pan et al. [29] concluded that the greatest affection likely occurs after 10 days from symptoms initiation.
Comparing both lexicon performance, almost perfect agreement in COVID-RADS was found among the three observers (K = 0.82). On the other hand, A substantial agreement with the three observers’ overall reliability (Κ = 0.78); similar results were also reported in Prokop et al. [10]. Also, Inui et al. [12] reported that both CO-RADS and COVID-RADS provided a reasonable agreement in COVID-19 reporting of chest CT findings.
On the other hand, Prokop et al. documented that the indeterminate category CO-RADS-3 offered little diagnostic efficacy as a declaration of the COVID pandemic. This could explain that the COVID-RADS lexicon did not include a grade for indeterminate lesions.
In the current study, radiologists’ recorded that both lexicons feasibility are 100% with possible assignment in all cases, and both lexicons are easily applied in more than 90% of cases according to their interpretation among the different levels of COVID-19 affection. Moreover, the observers preferred COVID-RADS with a higher percentage in more than 50% of the cases.
We attribute this preference to the fact that COVID-RADS includes clear CT findings for the different typical and atypical findings. Also, employing this lexicon is done by revising, checking the criteria, and ticking a checklist of each case, hence detecting the grade and reflecting the suspicion of viral infection, besides the proper organization of the COVID-RADS lexicon as its postulation was based on an evidence-based systemic review.
In contrast, the Dutch group developed the CO-RADS score in the pandemic’s acute stage with rapidly increasing cases and resource restrictions. This was acknowledged among their limitations [10].
Among this study’s advantages are the multicentric enrollment with different exposure levels to the COVID-19 pandemic to formulate a representative sample from four different centers to COVID affection.
Although the radiologists’ experiences are very close with narrow differences, we did not face significant differences in interpretation, and this confirms the applicability of both scores and endorses the employment of the RADS lexicon within a structural report.
Few limitations face the current study: the retrospective nature of the study, the non-inclusion of the severity score of lung affection, and the unavailability of the median interval between imaging and RT-PCR.
On facing the global emergency of COVID-19, we recommend employing a structured report form to fully facilitate the interpretation and improve communication with referring clinicians to conquer the time factor in the management of suspected COVID patients, basing the final diagnosis on clinical, laboratory, and imaging findings and finally a confirmed RT-PCR assay.