Comparison of RT-PCR and thorax CT findings in the diagnosis of patients with symptoms in viral pneumonia caused by sars-COV-2

The gold standard diagnostic method in the diagnosis of COVID-19 is the reverse transcription polymerase chain reaction (RT-PCR) test, which is obtained from throat and nose swabs and detects viral RNA. In symptomatic patients, thorax computed tomography (CT) can identify COVID-19 infection at an early stage. Ground glass opacities, multifocal patchy consolidation and / or peripherally distributed interstitial changes have been considered typical thorax CT findings for COVID-19. In this study, we aimed to investigate the relationship between clinical and laboratory findings and RT-PCR and thorax CT findings, and the diagnostic performance of thorax CT in symptomatic and hospitalized patients. The study was conducted with a total of 408 patients hospitalized in the pandemic clinic. There were 176 patients with positive RT-PCR test and thorax CT findings compatible with COVID-19 pneumonia, 181 patients with negative RT-PCR test and thorax CT findings compatible with COVID-19 pneumonia, and 51 patients with RT-PCR test positive and normal thorax CT findings in our study. All patients included in the study were symptomatic, and RT-PCR test and thorax CT were performed routinely for the diagnosis of COVID-19. The study population consisted of 164 women (40.2%) and 244 men (59.8%). The age range of the patients was 34-86 years and the mean age was 45.2 ± 16.7 years. Concomitant disease rate was 35.8% (n: 146). The distribution of symptoms was determined as cough (65.2%), fever (40.7%), weakness (35.3%) and shortness of breath (32.6%). While the PCR test was positive in 55.6% (n: 227) of the patients, the PCR test was negative in 44.4% (n: 181). While CT findings were detected in 87.5% (n: 357) of the patients, the CT result was normal in 12.5% (n: 51). Typical CT findings were found in 74.3% (n: 303) of those with CT findings, and atypical CT findings were found in 13.2% (n: 54). There were CT findings in 77.5% of those with positive PCR test. Typical CT findings were found in 62.1% of these and atypical CT findings were found in 15.4%. In 32 (14.1%) of 227 patients with positive PCR test, the first PCR result was negative and positivity was detected in the 2nd or 3rd PCR results. Of these 32 patients, 65.6% (n: 21) had typical CT findings, 6.2% (n: 2) had atypical CT findings, while 28.1% (n: 9) had no CT findings. Shortness of breath in typical CT group (normal CT; 11.8% vs typical CT; 36.6% vs atypical CT; 29.6% p = 0.001), sore throat in normal CT group (normal CT; 41.2% vs typical CT; 19.8% vs atypical CT; 22.2% p = 0.005) were higher than the other groups. Myalgia (22.0% vs 13.3%; p = 0.022), fatigue (39.6% vs 29.8%; p = 0.039) and headache (18.1% vs 9.4%; p = 0.013 ) were higher in patients with positive PCR test compared to negative ones. In laboratory parameters, CRP level (10.1 vs 3.5; p <0.001), D-dimer level (0.4 vs 0.3; p = 0.031), ferritin level (126.9 vs 46.8; p < 0.001) and IL-6 level (8.9 vs 3.8; p = 0.001) were found to be higher in patients with CT findings compared to those with normal CT results. In our study, the mean age of patients with CT findings was higher than patients with normal CT results (46.6 ± 16.6 vs 35.8 ± 13.8; p <0.001). Male gender (62.5% with CT finding; 41.2% with normal CT findings, p = 0.006) and the presence of comorbidity (38.1% with CT findings; 19.6% with normal CT results, p = 0.012) were significantly higher in patients with CT findings. When the PCR results were taken as a reference, the sensitivity of thorax CT in demonstrating COVID-19 infection was 77.6%. As a result; in our study, thorax CT results were found to be significant in detecting COVID-19, whereas RT-PCR test continues to be the gold standard diagnostic tool in diagnosis for now. However, contact history, clinical findings and imaging findings should be evaluated together in the diagnosis of COVID-19 in patients with negative RT-PCR test. Patients with typical CT findings should be isolated and the RT-PCR test should be repeated to avoid misdiagnosis. Especially, in patients with high mortality in the presence of advanced age and comorbidity, even if the PCR result is negative, thorax CT performed at the time of admission is very important for the early diagnosis of the disease. Keywords: COVID-19, pneumonia, RT-PCR, thorax CT