Introduction
COVID-19 is a zoonotic disease caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). The virus was previously known as Wuhan virus or 2019 novel coronavirus (2019-nCov).[1] SARS-CoV-2 is the coronavirus responsible for the COVID-19 pandemic of 2020.[2] The first cases of the highly transmissible respiratory viral infection were observed in Wuhan city, China, between November and December 2019 and quickly spreading to different parts of the world.[1,2,3,4] The mean incubation time is 5.1 days (95% confidence interval [CI]: 4.5–5.8 days), with 97.5% of those who develop symptoms within 11.5 days (95% CI: 8.2–15.6 days).[5] Mortality rates are currently unknown but ranges from 0.25% to 10%. Currently, no vaccine or definitive treatment are available.[5] The action of the SARS-CoV-2 virus which results in COVID-19 disease is not fully understood.[6] The virus is a novel human infecting Betacoronavirus likely originating from chrysanthemum bats.[7] It acts by infecting the angiotensin-converting enzyme 2 receptor in human host cells, which is typically expressed in Type II alveolar cells in the lungs and may explain the clinical presentation of COVID-19 disease with upper and lower respiratory tract symptoms.[7]
The mode of transmission of the SARS-CoV-2 virus is through respiratory droplets; but has also been found in blood and stool with severe manifestations commonly seen in males, particularly in the elderly.[3,7,8] Clinical manifestations include fever, dry cough, fatigue, myalgia, headache, sore-throat, abdominal pain, and diarrhea.[3,6,7]
The role of imaging in the diagnosis of COVID-19 is still under debate.[9] However, chest imaging has been considered as part of the diagnostic workup of patients with suspected or probable COVID-19 disease where reverse transcriptase polymerase chain reaction (RT-PCR) is not available, or results are delayed or are initially negative in the presence of symptoms suggestive of COVID-19.[10] Imaging has been also considered to complement clinical evaluation and laboratory parameters in the management of patients already diagnosed with COVID-19.[11] Moreover, chest radiography is widely available and has reduced infection control issues that currently limit the utilization of chest computed tomography (CT) in COVID-19.
Several studies from Asia have analyzed and described the chest CT findings at the presentation and at different times throughout COVID-19 disease course.[12,13] During the subsequent outbreak in the Western world, chest radiographs (CXRs), together with arterial blood gas analysis and clinical presentation, in patients positive to RT-PCR, was recommended as a useful and easily available tool to support the initial diagnosis and for the subsequent management of COVID-19 patients.[14,15] Nonetheless, data specifically addressing CXR findings in COVID-19 are still limited[16,17,18] with marked paucity of studies about imaging findings in COVID-19 from west African population including Nigeria. A lot of the available literature about the radiographic manifestations of COVID-19 disease is mainly from Asian and European countries. Furthermore, the role of lung ultrasound is probably valuable but still unclear.[19]
However, as Nigeria battles the challenges of curtailing COVID-19, successful strategy will largely depend on a sound understanding of the imaging profile of COVID-19 cases in our population.[20] A locally focused analysis of chest radiographic findings might help identify the defining imaging characteristics and share experience with clinicians at the frontlines of case management. Hence, we described the chest radiographic findings of COVID-19 pneumonia among Nigerians in a large urban city of Kano, Northwest-Nigeria which was one of the epicenters of COVID-19 disease outbreaks in the country.
Materials and Methods
This was a retrospective study where data were collected from four hospital/medical imaging facilities that were very active during the pandemic in Kano Metropolitan area. These facilities served a city population of approximately 3.6 million persons.
All consecutive patients with confirmed SARS-CoV-2 infection by a positive result on (RT-PCR) testing of a nasopharyngeal sample, according to international guidelines[21] and also underwent CXR examinations between April 21, and May 28, 2020 were included. Local Institutional Review Board ethics approval was obtained before commencement of the study.
Data were collected from the SYNAPSE (5.3.300.60. PACS) 2015–2020 Fujifilm Medical Systems USA., Inc., reporting database, and information regarding age, gender, clinical presentation and imaging findings of patients were also recorded.
The posterior-anterior frontal CXRs were performed in erect position unless if the patient was too sick. In such cases, the radiographs were obtained as anterior-posterior in supine positions. All radiographic examinations were performed with static conventional radiography units and were processed with either FUJI® or AGFA® computed radiography systems. All standard precautionary protocols for imaging COVID-19-positive persons were adhered to in handling patients. The processed X-ray images were reviewed on a local area network workstation by at least two radiologists with minimum of 5 years of postfellowship experience. All results were compared, and when disagreement was found, final decisions were determined by consensus.
The findings considered in the evaluation of CXR were the presence or absence and the type of pulmonary lesions/abnormality, and their distribution.
CXR lesion(s) [Figure 1] were defined according to the Fleischner Society's nomenclature, available in the Glossary of Terms for Thoracic Imaging.[22]
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Figure 1:
Chest radiographs showing bilateral peripheral ground-glass opacity (a) and right lower zone reticulations (b) in COVID-19 patients
- Consolidation, as a homogeneous increase in pulmonary parenchymal attenuation that obscures the margins of the vessels and airway walls
- Ground-glass opacity (GGO), as an area of hazy, increased lung opacity, usually extensive, within which margins of pulmonary vessels may be indistinct.
The distribution of CXR lesions or abnormalities was classified as unilateral or bilateral. Within each hemithorax, the craniocaudal distribution of the lesions was evaluated on the basis of the involvement of the upper, middle, and lower zones. The middle zone was defined as the lung area delimited by (included between) two horizontal lines at the level of the superior and inferior hilar horns, respectively; the upper zone was defined as the lung area included between the horizontal line at the level of the upper hilar horn and the apical pleura; the lower zone was defined as the lung area included between the horizontal line at the level of the inferior hilar horn and the diaphragm. The horizontal distribution of the lesions was evaluated on the basis of the involvement of the peripheral zone only, the central zone only, or both. Central zones were defined as the central area within 2 cm from the lobar bronchial structures as far as visible; peripheral zones were defined as the remaining lung area between the central zones and the pleura.[9,23]
The statistical analysis was performed using IBM SPSS Statistics Software (version 23; IBM, New York, NY, USA) continuous variables were expressed as mean ± standard deviation (SD) values. The frequency of the radiographic findings was expressed as the number of occurrences and percentages. Frequencies in the different gender were compared using the Chi-square test; P < 0.05 was considered statistically significant.
Results
A total of 125 radiographs of SARS CoV-2-positive patients were studied, among which, 27 (21.6%) were female while 98 (78.4%) were male as shown in Figure 2. Their mean age was 57.3 ± 12 years (range 23–96). Majority (29.6% and 26.4%) of the COVID-19 patients in the present study were in the 50–59- and 60–69-years' age groups, respectively, while 16.8% were in the 70 years and above groups and very few (4.8%) were <40 years as shown in Table 1.
Figure 2:
Chart showing gender distribution of COVID-19 patients
Table 1:
The age groups of COVID-19 patients
Although males were found to be older than their female counterpart, no significant difference was observed (mean age, 57.4 years [SD, 11] and 56.7 years [SD, 17] for males and females respectively, P = 0.864).
One hundred and one (80.8%) of them had abnormal chest finding while 24 (19.2%) of them were found to have normal CXRs [Figure 3]. There was a statistically significant difference between normal/abnormal chest radiographic findings and age among the patients (P = 0.006).
Figure 3:
Chart showing radiographic findings on chest radiographs of COVID-19 patients
The most common symptoms patients presented with were cough, fever, shortness of breath (SOB), and body weakness [Table 2]. Besides, patients in the 5th–7th decades showed nonsignificant higher occurrences of anosmia 27.5% than those in other decades of life (P > 0.05).
Table 2:
Associations between symptoms and radiographic findings with age groups in COVID-19 patients
The occurrences of GGO, lesion affecting both lungs and lower zones affectation associated well with age [Table 2]. GGO was significantly seen in 43 (62.3%) of COVID-19 patients who are between 40 and 60 years and in 40 (85%) of patients who are more than 60 years but only seen in 4 individuals who are <40 years (P < 0.05).
Age was also found to be significantly associated with the presence of alteration in the radiographs on Chi-square tests (P = 0.006, χ2 = 9.989, df = 2). On the other hand, the presence of abnormal CXR findings or otherwise had nothing to do with the sex of the individual (P = 0.653, χ2 = 0.203, df = 1) on Chi-square statistics. Likewise, no significant differences were observed among fever, cough, vomiting, and SOB between the two groups (P > 0.05).
Binary logistic regression analysis of socio-demographic characteristics and symptoms for normal/abnormal chest radiographic findings in COVID-19 Pneumonia revealed that, of all the parameters studied, anosmia and age were respectively the only ones that could independently predict if the COVID-19 patient may likely come down with the abnormal alteration in the CXR or not (0.175 [0.057–0.542] P = 0.002; 3.7 [1.423–9.622] P = 0.007).
Discussion
The recommendation for COVID-19 in patients positive to RT-PCR includes CXR, together with arterial blood gas analysis and clinical presentation. CXR is recommended as a useful and easily available tool to support the initial diagnosis and for the subsequent management of COVID-19 patients.[14,15] Nonetheless, data specifically addressing CXR findings in COVID-19 are still limited.[16]
Chest radiography is a quick and easy method, frequently requested due to its wide availability and low cost. The advent of portable devices has allowed its use in intensive care units and field hospitals.[24]
In general, it is not indicated for asymptomatic patients or those with mild symptoms of the disease. Imaging should be reserved for those with moderate-to-severe symptoms, those with risk of progression (presence of comorbidities), and those with worsening of the respiratory condition.[21,24] In environments with limited resources, imaging can eventually be indicated as a method for medical triage of patients with moderate to severe clinical features and a high pretest probability,[14] in whom urgent decision-making is of primary importance.
The use of chest imaging in COVID-19 suspected cases does not replace specific diagnostic tests such as the detection of viral RNA by reverse transcription polymerase chain reaction (RT-PCR) and serological detection of antibodies to SARS-CoV-2. Moreover, most medical societies do not recommend the use of imaging as a method of disease screening.[24,25,26]
A total of 125 CXRs were studied, among which, 27 (21.6%) were female while 98 (78.4%) were male. The findings by Samuel et al. is that among the 168 patients for whom gender was reported, 124 (74%) were male.[27] This is similar to the findings in our own study where males constitute 78.4% of the infected patients, this pattern is likely due to greater mobility with respect to economic interactions and the predominant culture of handshaking during pleasantries among males in our environment which exposes them to greater risk of contracting COVID-19.
Similarly, the mean age of our patients was 57.3 ± 12.3 years (range 23–96) is slightly lower than what was reported by Samuel et al., who found the mean age to 67.5 years. This may be attributed to the fact that the average life expectancy in Nigeria is lower when compared to Western countries.[27]
The most common presenting complaint was cough which was seen in 78.6% of patients followed by fever which is seen in 62.7% of patients. SOB and body weakness constitute 57.9% and 58.6%, respectively. The most common presenting symptoms in Asia and European were fever and cough, which is typical of the epidemiology of the disease. The study by Bowale et al. however found fever to be the most common symptom.[20]
Anosmia constituted 22.2% and together with loss of sense of taste seems to be the rising new symptoms being experience in our study area. A diminished ability to smell or taste, as reported by some patients has been recommended to be added to the list of primary symptoms for COVID-19 in the USA and Britain as a result of the frequency of their occurrence.[28] A study conducted in the USA among COVID-19 positive and negative individuals revealed that these two symptoms showed the largest magnitudes of association with COVID-19 when compared to other symptoms.[29] Inclusion of loss of smell or taste in primary screening for COVID-19 could potentially be useful in the Nigerian context especially as these symptoms typically manifest in the early stage of disease or when the patient's condition is mild.[28,29]
There are 80.8% positive radiographic findings noted in the CXR s of the patients in this study while 19.2% were normal. This is higher than what was reported by Wong et al.,[16] while reviewing 255 CXR in 64 patients, describing the time course of the radiographic findings of COVID-19 pneumonia, reporting an overall rate of negative baseline CXR examinations of 31%. Similarly, Farias et al. found out that the overall rate of normal CXR findings in patients with positive RT-PCR was 25%, versus an overall rate of normal chest CT of 0%–22% reported in the literature.[16,30] The lower number of normal recorded in our study when compared to others may be attributed to the fact that patient do present late in our environment and thus the manifestation of radiographic changes in a greater percentage of our patients.
In this study, the most frequent chest radiographic finding was ground-glass appearance (GGO) and reticular pattern, alone or in combination with other opacities, and this represent the radiographic appearance described in other coronavirus-related pneumonias.[31,32,33] Ground-glass constituted 69% and 44.8% of the radiographic findings either alone or in combinations. Same with reticulations which was seen in 19.8%. Pulmonary parenchymal consolidation was constantly less frequent than the other two alterations, especially in the early phase of the disease as documented.
The distribution of the opacities in our cases is bilateral, and this is similar to the pattern of distribution described in H1N1 influenza pneumonia in which the distribution of the lesions is in the middle fields with relative sparing of the superior fields. In accordance with the observations of Wong et al.,[16] in the majority of the patients, the alterations were bilateral, and in patients with unilateral lesions, no predominance was observed between left and right.
The GGO is seen in the periphery in about 71.3% while it is central in 13.7%. There is affectation of the middle lobe more than other lobes with 48% of the lesions noted in the middle lobe. The exclusive peripheral involvement and the combination of peripheral and central distributions were significantly more frequent than exclusive central distribution, without significant modifications of their proportions in the different time intervals.
Several studies reported a predominant, although not significant, localization of the lesions in the lower lobes;[33,34] our results confirm this observation and measured a significantly higher frequency of involvement of the lower fields compared to the middle fields, and of the lower and middle fields compared to the upper fields.
Conclusion
We have confirmed the importance of CXR as an adjunct in the diagnosis of COVID-19 and have established the radiographic findings of GGO, reticulations and Consolidation as the basic features of COVID-19 pneumonia. We have also established the bilateral and peripheral pattern of distribution with older age and anosmia being the major independent predictors of chest radiographic abnormalities.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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