In December 2019 in Wuhan-China patient 0 was diagnosed with what will become a worldwide deadly pandemic, starting the third corona virus pandemic, the most extensive and deadliest thus far [1] . To date, almost 6 million deaths have been recorded at globally for over 400 million of cases reported [2] . COVID-19 is a disease caused by SARS (Severe Acute Respiratory Syndrome) COV 2. It is a respiratory RNA [3] [4] virus transmitted in humans through saliva droplets. Its pathogenesis is associated with respiratory tropism [4] [5] [6] which is responsible for, among other things, serious broncho-alveolar lesions resulting in an overall lethality less than 2% [2] .

Even though Sub Saharan Africa remained least affected, most African countries had registered multiple cases such as Tunisia, which is the most affected African country. These countries organized the fight against this disease and are currently administering COVID-19 vaccines. In Cameroon more than one million doses have been administered with a dose administration rate of 6856 per 100,000 [2] which means only 7.8% of the target [7] . However, the pandemic is still ongoing with various mortality rates depending on the country [2] . With emerging variants, it is quite important to describe the clinical features of the acute infection within the different waves, and the process and reliability of diagnosis, characteristics of the disease, comorbidities and aged-related risks. More importantly, a description of the clinical manifestations of the disease in the lungs.

In Cameroon, the first case was diagnosed on 6th March 2020 [8] . The health system’s response was organized around management confirmed cases in designated COVID-19 treatment centers (CTC), while other hospitals dealt with suspected cases with timely reference to CTC when the diagnosis was confirmed. Majority of health facilities followed a management algorithm based on: first, the clinical assessment of the patient to determine if the patient profile fit a suspected case, second, the diagnosis had to be confirmed by PCR/Rapid diagnostic tests. The confirmed cases were then classified according to the severity. The initial paraclinical tests required only a chest X-ray, and did not include Computerized Tomography (CT) scans even in patients with severe symptoms [9] . Considering the low testing capacity at the early stage of the outbreak and the interest of the scientific community for CT scan as an alternative, we designed this study to assess the correlation between abnormalities of the lung detected by CT scan and its reliability in detecting and confirming active COVID-19 infection.

This work primarily aimed to assess the predictive value of lung CT scan for the diagnosis of COVID-19 disease. The main resulting observations on the study population are similar to previous data on male predominance amongst COVID infected patients [13] [14] . Most patients came to the hospital for symptoms found in the top 3 of a study in France [15] . However, our observations differ from the one observed in Cameroon [14] . Possibly, due the differences of the samples, as our center was primarily reserved for suspected cases before transfer to COVID-19 centers, the rate of positivity for the COVID test was comparatively lower than the one reported at dedicated COVID-19 care sites, which welcomed both suspected and confirmed cases [9] [14] . Apart from the age of our suspected patients, the factors associated to COVID-19 disease reported in the literature were not found in our population, in particular comorbidities and sex [9] [14] [16] [17] . However, age was found to be associated with both the occurrence and severity of COVID-19 disease [17] . Regarding abnormalities of the lung parenchyma, we found a high rate of scannographic abnormalities in patients with a negative COVID-19 PCR test. This is consistent with data from the literature, which supports the indication of a lung CT scan in case of pulmonary clinical signs in suspected patients despite a negative PCR test [17] . The type of lung abnormalities observed in this setting follows the knowledge previously gathered; stating that of all the lesions observed ground glasses lesions are the first type of lesions observed in COVID-19 cases [18] . Our finding shows clearly that PCR positive patients had the same lung impairment as the negative ones this might be explained by the rage of etiology corresponding to the ground glasses lesion as MOUBACHIR et al. found [19] . They stated the main etiology is sarcoidosis it was confirmed by M.Zerraa et al. [20] . Although these two studies can be seen as outdated for not being cotemporary to COVID-19; they certainly demonstrate the wide range of etiologies when it comes to ground glasses lesions (from pulmonary edema to auto immune disorder) explaining the great number of negative PCR. Our data confirm the low sensitivity of pulmonary computed tomography for the diagnosis of COVID-19, and reinforce the need for precise indications for this examination [21] . However, other prior studies show discordant results to our findings [22] [23] . On the one hand, Ai T. et al. found good sensitivity and poor specificity. This difference might be due to the larger sample size based only on COVID-19 confirmed cases. On the other hand, a study by Fang Y, et al. had a sample like ours but was constituted solely of confirmed cases resulting in a good sensitivity. KHERAD et al. [24] have emphasized the imperfect sensitivity and limited specificity including the limitation of access to timely CT scans. Altogether, the increase in the use of CT scans around the world has led to contradictory guidelines [25] [26] . Meanwhile, lung CT scans are useful in the initial phases of COVID-19 infection for specific indications [26] included in diagnostic algorithms in the presence of pulmonary symptoms and respiratory distress. Finally, Cameroonian data are very different to those observed in Italy, which showed a very high predictive positive value for the CT scan making it good reference for recognizing COVID-19 patients while waiting for RT-PCR confirmation [27] . In our context, we found a low sensitivity with a too large confidence interval but a relatively good specificity with an acceptable positive predictive value but with a large confidence interval. These data’s disqualifies the computed tomography as a diagnostic tool for COVID-19. The differences in our conclusion are explained by the procedures used in the study in Italy where PCR was repeated multiple times when the computed tomography was suggestive.

In conclusion, in this setting, lung CT scan for detection of COVID-19, shows poor sensitivity and better specificity. The poor performances of CT scans for COVID-19 infection diagnosis as compared to PCR diagnosis confirm the former as a “NO GO” for the diagnosis of COVID-19. However, it suggests that CT scans may be more suitable to assess severity, monitor the evolution and exclude other diagnoses as recommended elsewhere.

Administrative authorization was given by the Essos Hospital Center for this study. As part of the monitoring of pandemic data, a specific ethical clearance (2020/13/CE-CHE) was granted, and all data were anonymized with a single identifier.

NA.

All data and materials are available upon request.

The authors are grateful to all the staff of the dedicated sector of suspected COVID-19 cases in Essos Hospital Center during the first wave in 2020.

Study design: LB, SA, SNN, AENN;

Data collection LM, MN, BM and CS;

Data curation: ABS, SA, AENN;

Data analysis ABS;

Supervision AENN;

Writing initial draft: LB and AENN;

Editing: AENN, ABS, CS.

All authors reviewed and approved the final version.

The authors declare no conflicts of interest regarding the publication of this paper.

Nlend, A.E.N., Bonyomo, L., Abogo, S., Nomo, S.N., Meka, L., Nna, M., Meva’a, B., Sandie, A.B. and Nsahlai, C. (2023) Optimum Threshold Estimation of Thorax CT Scan for COVID-19 Diagnosis in a Single Center in Cameroon. Advances in Infectious Diseases, 13, 12-20. https://doi.org/10.4236/aid.2023.131002