ABSTRACT
Molecular diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by real-time reverse transcription polymerase chain reaction (RT-PCR) in respiratory specimens is considered the gold standard method. This method is highly sensitive and specific but it has some limitations such as being expensive and requiring special laboratory equipment and skilled personnel. RapidFor™ Antigen Rapid Test Kit is a commercially available Ag-RDT which is produced in Turkey and designed to detect the nucleocapsid antigen of SARS-CoV-2 in nasopharyngeal swab samples. The aim of this study was to evaluate the performance of this novel SARS-CoV-2 antigen detection considering the RT-PCR method as the gold standard. Four hundred forty-four nasopharyngeal swab samples which were collected from the patients who met clinical criteria of COVID-19 from ten centers in Turkey between September 2020 and February 2021 were included in the study. All the nasopharyngeal swab samples were tested for SARS-CoV-2 RNA using commercial RT-PCR kits (Bioeksen and A1 Lifesciences, Istanbul, Turkey) according to the manufacturer's instructions. Viral loads were assessed according to the cycle threshold (Ct) values. RapidFor™ SARS-CoV-2 antigen test (Vitrosens Biotechnology, Istanbul, Turkey) was used to investigate the presence of SARS-CoV-2 antigen in all samples following the manufacturer's instructions. Out of 444 nasopharyngeal swab samples tested, 346 (77.9%) were positive and 98 (22.1%) were negative for SARS-CoV-2 RNA by RTPCR. Overall sensitivity of the RapidFor™. Antigen Rapid Test Kit was 80.3% whereas specificity was found to be 87.8%. Positivity rate of rapid antigen test in samples with Ct values over 25 and below 30 was 82.7%, while it increased to 95.7% in samples 20 ≤ Ct < 25 and reached 100% in samples with Ct values below 20. RapidFor™ SARS-CoV-2 Ag test might be a good choice in the screening of symptomatic and asymptomatic patients and their contacts for taking isolation measures early, with advantages over RT-PCR as being rapid, easy and being applicable in every laboratory and even at point of care.
ABSTRACT
OBJECTIVES: To evaluate the diagnostic value of the rtRT-PCR test and CT in patients presenting with typical clinical symptoms of COVID-19. METHODS: The study with the participation of four center in Turkey was performed retrospectively from 20 March-15 April 2020 in 203 patients confirmed for COVID-19. The initial rtRT-PCR test was positive in 142 (70.0%) of the patients (Group-I) and negative in 61 patients (Group-II). RESULTS: The mean age of the patients in Group-I was 49.7±18.0 years and the time between the onset of symptoms and admission to the hospital was 3.6±2.0 days; whereas the same values for the patients in Group-II were 58.1±19.9 and 5.3±4.2, respectively (p=0.004; p=0.026). Initial rtRT-PCR was found positive with 83.5% sensitivity and 74.1% PPV in patients with symptom duration of less than five days. It was found that rtRT-PCR positivity correlated negatively with the presence of CT findings, age, comorbidity, shortness of breath, and symptom duration, while rtRT-PCR positivity correlated positively with headache. Presence of CT findings was positively correlated with age, comorbidity, shortness of breath, fever, and the symptom duration. CONCLUSIONS: It should be noted that a negative result in the rtRT-PCR test does not rule out the possibility of COVID-19 diagnosis in patients whose symptom duration is longer than five days, who are elderly with comorbidities and in particular who present with fever and shortness of breath. In these patients, typical CT findings are diagnostic for COVID-19. A normal chest CT is no reason to loosen up measures of isolation in patients with newly beginning symptoms until the results are obtained from the PCR test.
ABSTRACT
OBJECTIVES: Severe acute respiratory syndrome-coronovirus-2 is a global public health problem, in which early diagnosis is required to prevent the spread of infection. In this study, we aimed to reveal the diagnostic value of chest computed tomography (CT) imaging with respect to symptom duration. METHODS: This retrospective study involved patients from five centers, who were admitted with typical COVID-19 symptoms and found to be positive for COVID-19 real-time reverse transcription-polymerase chain reaction (rtRT-PCR) test. RESULTS: One hundred and five patients with positive COVID-19 rtRT-PCR test were involved in the study. Sixty percent of these patients had chest CT imaging findings consistent with COVID-19 pneumonia. The most common chest CT finding was bilateral and subpleural ground-glass opacity in middle-lower lobes of the lungs. Chest CT findings were detected in 85.1% of the patients with a symptom duration of more than 2 days. In receiver operating characteristic analysis of this parameter, area under the curve (AUC) was 0.869, while sensitivity and specificity were 90.5% and 76.2%, respectively. It was notable that chest CT findings were 7.17 times more common among the patients aged 60 years and older, with AUC, specificity, and positive predictive value of 0.768, 88.1%, and 84.8%, respectively. CONCLUSION: Chest CT imaging is a quite valuable tool in patients with longer than 2 days' duration of symptoms, in whom clinical and epidemiological data support the diagnosis of COVID-19 infection. We suggest that the diagnosis of COVID-19 pneumonia should be made with chest CT imaging when rtRT-PCR test cannot be performed or gives a negative result, which is important for public health and to prevent the spread of infection.