Journal of Preventive Medicine

Introduction
The outbreak of a recent viral pneumonia (COVID-19) has caused global concern. This virus quickly spread to other parts of the world and caused a pandemic [1]. In Iran, the first cases of infection with this virus were officially announced in February 2020, which included 43 cases of infection and eight deaths [2]. The diagnosis of this disease is based on laboratory tests, radiographic findings, and clinical manifestations. Considering the existence of infected people without clinical symptoms [15]or having a negative PCR [16], as well as the flood of official and unofficial information, there is a need to rely on evidence-based findings to improve the quality of health care [17]. In this regard, there is a need to further investigate and compare existing diagnostic methods such as PCR, CT scan, and blood tests and determine the degree of alignment between them. Despite the relatively large number of studies that have been conducted in the fields of clinical, radiographic and laboratory manifestations of COVID-19, limited studies have investigated the relationship between the results of throat smear test, laboratory tests, and radiological tests in patients. Therefore, in this study, we aim to examine the compatibility of the results of the three diagnostic methods of laboratory tests, lung CT scan, and RT-PCR with each other in suspected and confirmed COVID-19 patients.

Methods
This is a retrospective study. The study population consisted of all 400 suspected patients with COVID-19 referred to Musa bin Jafar Hospital in Quchan, Iran from February to April 2020, for whom blood tests, lung CT scan, and pharyngeal swab RT-PCR were performed in the hospital. Sampling was done by census method. Inclusion criteria: Admission to hospital suspected of COVID-19 and receiving treatment for COVID-19, performing all three paraclinical procedures (blood test, lung CT scan, and pharyngeal RT-PCR) for the patient in the hospital with documentation. After obtaining persimmons, the information including 5 laboratory tests (WBC, lymphocyte count, CRP, LDH, and ESR), the written report of lung CT scan by the radiologist, and the result of the RT-PCR test of the oropharyngeal swab were extracted from the patient’s medical records. Of 400 patients, 221 eligible samples were included in the study and their data was analyzed using descriptive and inferential statistics including chi-square test and Cramér’s V statistic in SPSS software, version 19.

Results
The mean age of patients was 60±11.4 years; 48.2% were male and 51.58% were female. Based on the results, most patients with positive RT-PCR also had a positive lung CT scan result (76%), but it was not statistically significant based on the chi-square test results (P=0.118). A number of patients with positive RT-PCR results also had a positive blood test (47.8%), and it was statistically significant (P=0.02). The relationship value between these two variables using Cramér’s V statistic was 0.186. Most people with a positive blood test result also had a positive lung CT scan result (71.9%), and it was statistically significance (P=0.019; Cramér’s V= 0.231). No significant correlation was found among the positive lung CT scan results, positive blood tests, and positive RT-PCR results.

Conclusion
Blood tests were positive in 37.1% of participants, while positive lung CT scan was reported in 66.5%, and positive RT-PCR results in 32.1%. Different results have been reported in different studies, but they all have indicated the importance of performing lung CT scan in the early stages of the disease despite the initial clinical symptoms. A case study [22] showed that COVID-19 patients without symptoms in blood tests and with negative PCR can have positive findings in lung CT scan, which indicates the greater importance of lung CT scan. 
In 27 patients, the results of all three diagnostic tools were positive; probably depends on the severity of the disease, which was not investigated. Also, 76% of patients with positive RT-PCR also had positive lung CT scan. It was reported as 72% in Xu et al.’s study [15]. Given the ease of access and rapid results of CT scanners compared to RT-PCR kits, CT imaging is the main COVID-19 screening tool. CT imaging plays an important role in the diagnosis of COVID-19, especially in the early stages of the disease (low viral load), while the swab test (PCR) may be negative. In addition, the differences in the results obtained from the PCR test of nasal, oropharyngeal, and bronchial swabs as well as the special standard conditions for storage, transfer, cultivation, and the interval between sampling and the result [26], require a regular process for accurate and timely diagnosis.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Mashhad University of Medical Sciences (Code: IR.MUMS.REC.1399.203).

Funding
This article is the result of the approved research project number 990255 with the financial support of the Research Vice-Chancellor of Mashhad University of Medical Sciences.

Authors' contributions
Analysis: Vahid Hajali; Sampling and scientific study of cases: Amin Irandost and Mehboobeh Behnejad; Drafting of the proposal: Amin Irandost and Bahareh Payvar; Editing: Hamid Bazazkahani.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The authors express gratitude to Mashhad University of Medical Sciences, especially the research assistant (project code 990225) for funding the research project, the chairmanship, respected management, supervisors and all the personnel of the medical and administrative departments of Musa ebn Jafar (AS) Ghochan Hospital. The authors wish good health and complete recovery to all patients affected by this dreaded virus.

References

1. Xiong Y, Liu Y, Cao L, Wang D, Guo M, Jiang A, et al. Transcriptomic characteristics of bronchoalveolar lavage fluid and peripheral blood mononuclear cells in COVID-19 patients. Emerg Microbes Infect. 2020; 9(1):761-70. [DOI:10.1080/22221751.2020.1747363] [PMID] [PMCID]
2. Tuite AR, Bogoch II, Sherbo R, Watts A, Fisman D, Khan K. Estimation of coronavirus disease 2019 (COVID-19) burden and potential for international dissemination of infection from Iran. Ann Intern Med. 2020; 172(10):699-701. [DOI:10.7326/M20-0696] [PMID] [PMCID]
3. WHO. WHO Coronavirus Disease (COVID-19) Dashboard [Internet]. 2020 [Updated 2020 October 29]. Available from: [Link]
4. Zhou P, Yang XL, Wang XG, Hu B, Zhang L, Zhang W, et al. A pneumonia outbreak associated with a new coronavirus of probable bat origin. Nature. 2020; 579(7798):270-3. [DOI:10.1038/s41586-020-2012-7] [PMID] [PMCID]
5. Wu F, Zhao S, Yu B, Chen YM, Wang W, Song ZG, et al. Author correction: A new coronavirus associated with human respiratory disease in China. Nature. 2020; 580(7803):E7. [DOI:10.1038/s41586-020-2202-3] [PMID] [PMCID]
6. El Zowalaty ME, Järhult JD. From SARS to COVID-19: A previously unknown SARS- related coronavirus (SARS-CoV-2) of pandemic potential infecting humans - Call for a One Health approach. One Health. 2020; 9:100124. [DOI:10.1016/j.onehlt.2020.100124] [PMID] [PMCID]
7. Torkian P, Ramezani N, Kiani P, Bax MR, Akhlaghpoor S. Common CT findings of novel coronavirus disease 2019 (COVID-19): A case series. Cureus. 2020; 12(3):e7434. [DOI:10.7759/cureus.7434] [PMID] [PMCID]
8. Eastin C, Eastin T. Clinical characteristics of coronavirus disease 2019 in China: Guan W, Ni Z, Hu Y, et al. N Engl J Med. 2020 Feb 28 [Online ahead of print] DOI: 10.1056/NEJMoa2002032. J Emerg Med. 2020; 58(4):711–2. [DOI:10.1016/j.jemermed.2020.04.004] [PMCID]
9. Kooraki S, Hosseiny M, Myers L, Gholamrezanezhad A. Coronavirus (COVID-19) outbreak: What the department of radiology should know. J Am Coll Radiol. 2020; 17(4):447-51. [DOI:10.1016/j.jacr.2020.02.008] [PMID] [PMCID]
10. Wu YC, Chen CS, Chan YJ. The outbreak of COVID-19: An overview. J Chin Med Assoc. 2020; 83(3):217-20. [DOI:10.1097/JCMA.0000000000000270] [PMID] [PMCID]
11. Huang C, Wang Y, Li X, Ren L, Zhao J, Hu Y, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet. 2020; 395(10223):497-506. [DOI:10.1016/S0140-6736(20)30183-5] [PMID]
12. Chen N, Zhou M, Dong X, Qu J, Gong F, Han Y, et al. Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: A descriptive study. Lancet. 2020; 395(10223):507-13. [DOI:10.1016/S0140-6736(20)30211-7] [PMID]
13. Karimi A, Tabatabaei SR, Rajabnejad M, Pourmoghaddas Z, Rahimi H, Armin S, et al. An algorithmic approach to diagnosis and treatment of coronavirus disease 2019 (COVID-19) in children: Iranian expert’s consensus statement. Arch Pediatr Infect Dis. 2020; 8(2):e102400. [DOI:10.5812/pedinfect.102400]
14. Tavakoli A, Vahdat K, Keshavarz M. [Novel coronavirus disease 2019 (COVID-19): An emerging infectious disease in the 21^st century (Persian)]. Iran South Med J. 2020; 22(6):432-50. [DOI:10.29252/ismj.22.6.432]
15. Xu X, Yu C, Qu J, Zhang L, Jiang S, Huang D, et al. Imaging and clinical features of patients with 2019 novel coronavirus SARS-CoV-2. Eur J Nucl Med Mol Imaging. 2020; 47(5):1275-80. [DOI:10.1007/s00259-020-04735-9] [PMID] [PMCID]
16. Di Paolo M, Iacovelli A, Olmati F, Menichini I, Oliva A, Carnevalini M, et al. False-negative RT-PCR in SARS-CoV-2 disease: Experience from an Italian COVID-19 unit. ERJ Open Res. 2020; 6(2):00324-2020. [DOI:10.1183/23120541.00324-2020] [PMID] [PMCID]
17. Baghcheghi N, Koohestani HR, Mesri M, Karimi M. [The need to pay attention to evidence-based medicine (EBM) in the diagnosis and treatment of COVID-19 disease (Persian)]. J Arak Univ Med Sci. 2020; 23(5):580-3. [DOI:10.32598/JAMS.23.COV.78.3]
18. Zu ZY, Jiang MD, Xu PP, Chen W, Ni QQ, Lu GM, et al. Coronavirus disease 2019 (COVID-19): A perspective from China. Radiology. 2020; 296(2):E1525. [DOI:10.1148/radiol.2020200490] [PMID] [PMCID]
19. Nasrollahzadeh Sabet M, Khanalipour M, Gholami M, Sarli A, Rahimi Khorrami A, Esmaeilzadeh E. [Prevalence, clinical manifestation and mortality rate in COVID-19 patients with underlying diseases (Persian)]. J Arak Univ Med Sci. 2020; 23(5):740-9. [DOI:10.32598/JAMS.23.COV.5797.1]
20. Fang Y, Zhang H, Xie J, Lin M, Ying L, Pang P, et al. Sensitivity of chest ct for COVID-19: Comparison to RT-PCR. Radiology. 2020; 296(2):E115-7. [DOI:10.1148/radiol.2020200432] [PMID] [PMCID]
21. Ai T, Yang Z, Hou H, Zhan C, Chen C, Lv W, et al. Correlation of chest CT and RT-PCR testing for coronavirus disease 2019 (COVID-19) in China: A report of 1014 cases. Radiology. 2020; 296(2):E32-40. [DOI:10.1148/radiol.2020200642] [PMID] [PMCID]
22. Huang P, Liu T, Huang L, Liu H, Lei M, Xu W, et al. Use of chest CT in combination with negative RT-PCR assay for the 2019 novel coronavirus but high clinical suspicion. Radiology. 2020; 295(1):22-3. [DOI:10.1148/radiol.2020200330] [PMID] [PMCID]
23. Wang D, Hu B, Hu C, Zhu F, Liu X, Zhang J, et al. Clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus-infected pneumonia in Wuhan, China. JAMA. 2020; 323(11):1061-9. [DOI:10.1001/jama.2020.1585] [PMID] [PMCID]
24. Rahimzadeh G, Ekrami Noghabi M, Kadkhodaei Elyaderani F, Navaeifar MR, Enayati AA, Manafi Anari A, et al. COVID-19 infection in Iranian children: A case series of 9 patients. J Pediatr Rev 2020; 8(2):139-44. [DOI:10.32598/jpr.8.2.139]
25. Li T, Lu H, Zhang W. Clinical observation and management of COVID-19 patients. Emerg Microbes Infect. 2020; 9(1):687-90. [DOI:10.1080/22221751.2020.1741327] [PMID] [PMCID]
26. Loeffelholz MJ, Tang YW. Laboratory diagnosis of emerging human coronavirus infections - the state of the art. Emerg Microbes Infect. 2020; 9(1):747-56. [DOI:10.1080/22221751.2020.1745095] [PMID] [PMCID]