key: cord-1033705-kczmhnjk
authors: Uysal, Emine; Kilinçer, Abidin; Cebeci, Hakan; Özer, Halil; Demir, Nazlım Aktuğ; Öztürk, Mehmet; Koplay, Mustafa
title: Chest CT findings in RT-PCR positive asymptomatic COVID-19 patients
date: 2021-01-30
journal: Clin Imaging
DOI: 10.1016/j.clinimag.2021.01.030
sha: 01bae531565c5a4687a62dce58de57a1ec0cf1b8
doc_id: 1033705
cord_uid: kczmhnjk

PURPOSE: To investigate chest computed tomography (CT) findings in asymptomatic patients tested positive for coronavirus disease (COVID-19) by reverse transcription-polymerase chain reaction (RT-PCR). MATERIAL AND METHODS: The chest CT images of 64 patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) who were RT-PCR test–positive but asymptomatic were retrospectively evaluated for the appearance and distribution of abnormal parenchymal findings. RESULTS: Of the 64 patients (mean age 59.4 ± 12; range 23–85), 42 (65%) were female, and 22 (35%) were male, and 16 (25%) of the patients had no abnormal findings on chest CT. Of the remaining 48 patients, lung involvement was bilateral in 32 (67%). Right upper lobe in 26 (54%), right middle lobe in 20 (42%), right lower lobe in 38 (79%), left upper lobe in 27 (56%), and left lower lobe were affected in 34 (71%) patients. The mean number of opacities detected in patients was 7.5 ± 5.7. The opacities were located only peripherally/subpleural in 22 (46%), only centrally/peribronchovascular in 5 (10%), and mixed in 21 (44%) patients. The frequency of pure ground glass opacities (GGO) was 63% GGO with a crazy-paving pattern or consolidation was 33%. Pure consolidation was detected in only two (4%) patients. Parenchymal opacities were only round in 27 (56%), only geographic demarcated in 3 (6%), only patchy in 2 (4%), and mixed in 16 (33%) patients. CONCLUSION: Chest CT was normal in only one-quarter of the asymptomatic patients. CT findings in asymptomatic COVID-19 patients were often peripherally located, mostly round-shaped GGO.

We retrospectively reviewed the RT-PCR test results of people isolated in quarantine between March 30, 2020, and May 1, 2020. Six hundred eighty-four patients with RT-PCRpositive were included in the study. Out of six hundred eighty-four individuals, 64 patients did not exhibit symptoms of the disease (fever, cough, sore throat, shortness of breath, weakness, muscle pain, fatigue, diarrhea, anosmia, and loss of taste). The patients who are initially (at the time of CT examination) or subsequently (during the 14 days in quarantine) symptomatic were excluded from the study. (Fig. 1.) . Chest CT images of asymptomatic patients were evaluated, and the findings were recorded.

All chest CT images were obtained using the Somatom Definition Flash (Siemens Healthcare, Erlangen, Germany) scanner without contrast. Patients were scanned from the apex to the base while holding their breath after inspiration in the supine position. The chest CT parameters were as follows: tube voltage 100-120 kV; slice thickness 3 mm; pitch 0.8; automatic tube current (Care Dose 4D) 50-180 mA; and matrix 512x512.

The CT images were independently examined by two radiologists with more than ten years' chest radiology experience. Final decisions were reached by consensus. In the inconsistency tomography. There was no difference in mean age between patients with abnormal findings on chest CT and those without (p>0.05).

Excluding the 16 patients with normal chest CT, forty-two (87.5%) patients had abnormal findings in the right lung parenchyma, while 39 (81.2%) patients had abnormal findings in the left lung parenchyma. Right and left lung involvement rates were very similar, and there was no significant difference (p >0.05).

The number of affected lobes in 48 patients with abnormal findings on chest CT is shown in Table 2 . Bilateral lung involvement rate and the frequency of the lobes affected in both lungs are indicated in Table 2 . Although the bilateral lower lobe percentage was higher, there was no significant difference between the lower and upper lobe involvement rates (p >0.05). The mean number of opacities detected in patients was 7.5 ± 5.7 (range 1-20), while it was 8.8 ± 6.1 (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) in females and 5.3 ± 4.3 (1-15) in males. The number of parenchymal opacities was not significantly different between genders (p = 0.05). No correlation was found between the number of parenchymal opacities and age (Fig. 5.) .

The appearance of lung opacities in patients is summarized in Table 3 . In our study group, the frequency of pure GGO was 62.5%, and GGO with crazy paving pattern or consolidation was 33.3%. Parenchymal involvement consisted of pure consolidation in only two (4.2%) patients. Also, four (8.4%) patients had a reverse halo sign (Fig. 6.) . The shape of lung parenchymal opacities in asymptomatic COVID-19 patients is shown in Table 3 .

Parenchymal opacities were only patchy in only 2 (4.1%) patients.

The localization of parenchymal opacities in the lungs in patients is shown in Table 3 .

Lesions are only centrally/peribronchovascular located in 5 (10.4%) of 48 asymptomatic patients with abnormal CT findings. Table 4 .

None of the patients had an atypical appearance, according to the RSNA consensus statement.

No accompanying findings such as pleural effusion, emphysema, bronchiectasis, or mediastinal or hilar lymphadenopathy were found on the chest CT of any patient. In a study with twenty-one symptomatic patients, the bilateral lung parenchymal involvement rate was reported as 76% [12] . Song et al., in their study of 51 symptomatic patients, reported the rate of bilateral involvement to be 86% [13] . In a study investigating the differences between COVID-19 pneumonia and influenza pneumonia, the bilaterality rate was 85% in J o u r n a l P r e -p r o o f Journal Pre-proof involvement was 67%. When our study results are compared with previous studies with symptomatic patients, we can say that the rate of bilateral lung involvement in asymptomatic patients is slightly lower than in symptomatic patients [12] [13] [14] . In studies conducted with symptomatic COVID-19 patients, no significant difference was reported between right and left lung involvement rates [15, 16] . Similarly, we found no significant difference between the two lung involvement rates in asymptomatic patients.

Song et al. reported a single-lobe involvement rate of 8% and the rate of five lobes' involvement as 39% in a series of 51 cases [13] . Liu et al. reported a single lobe involvement rate of 8% and a five-lobe involvement rate of 43% [14] . In our asymptomatic patient population, the rate of single lobe involvement was higher than in the studies mentioned at 31%. In 31% of our patients, all five lobes were affected, and this rate was lower compared to studies of symptomatic patients [13, 14] . As for which lobes are most affected, although the bilateral lower lobe was more affected, we did not find a significant difference between the rates for lower and upper involvement in asymptomatic patients. In some studies, similar to our study, there was no significant difference between the upper and lower lobes in terms of involvement in symptomatic patients, while the frequency of involvement of the lower zones was higher in some studies [12, 14, 16] .

As for the distribution of opacities, Han et al. reported the peripheral location rate of opacities as 90% in their 108 cases [17] . Studies have reported, respectively, the frequency of peripheral locations as 84%, 62.1%, and 45% [13, 14, 16] . In our study, 5 (10%) of 48 patients had opacities only in both lungs' central/peribronchovascular part. In the remaining 43 (90%) patients, peripherally/subpleural located (only or with central) opacities were present. Research to date shows that involvement is mostly in the peripheral areas of the lungs, as in our study, and the central parts of the lungs are less affected by this disease. Since J o u r n a l P r e -p r o o f Journal Pre-proof the blood and lymph flow is more intense in the peripheral (subpleural) lung parenchyma, the inflammatory response to the virus is considered to be stronger in this region, so the lesions are often peripherally located [18] .

In a study conducted with 24 asymptomatic patients, the rate of GGO was reported to be 50%

[10]. Han et al. detected ground glass opacities in 80% of 108 symptomatic patients, consolidation with GGO in 41%, and crazy paving pattern in 40% [17] . In another study of 101 symptomatic patients, the frequency of GGO was reported to be 86.1%; the frequency of consolidation was 43.6%. [19] . In their 130-case series, Wu et al. reported the rate of GGO to be 53.2%, and the rate of consolidation with GGO was 46.2% [18] . We found GGO (pure or with consolidation or crazy paving pattern) in 96% of our patients. This rate was higher in our patient group compared to the studies of symptomatic patients. The rate of total patients with consolidation (pure or with GGO) was determined to be 20% in our study, and this rate is quite low compared to the rate for symptomatic patients. Since the virus primarily invades the interstitium and causes thickening and edema in the interlobular, intralobular, and peribronchovascular interstitium, GGO appears early parenchymal finding. Consolidation J o u r n a l P r e -p r o o f

None of the patients had an atypical appearance, according to the RSNA consensus statement for CT reporting of suspected COVID-19 pneumonia

Our study has some limitations. First, the number of patients included in the study was relatively small. The second limitation is that children are not included in the study. Third, none of the patients had a follow-up CT chest. Finally, no inter-rater correlation was obtained

Three-quarters of asymptomatic COVID-19 patients had abnormal lung parenchymal findings on CT. GGO (pure or with crazy-paving pattern or consolidation) was the most common appearance of lung

Peripheral/subpleural (with or without central/peribronchovascular) was the most common localization of the disease. Round (with or without patchy) was the most common

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