Performance of Low-Dose Chest CT Scan for Initial Triage of COVID-19

Abstract

Background: Chest CT scan is frequently used for diagnosis of coronavirus disease 2019 (COVID-19), especially in regions with limited availability of reverse-transcription polymerase chain reaction test (RT-PCR) test. Low-dose CT of chest offers acceptable image quality with lower radiation dose, particularly important in younger patients. Objectives: We have designed the current study to evaluate the diagnostic efficacy of low-dose chest CT versus early RT-PCR results, for triage of COVID-19 patients. Patients and Methods: From February 20 to April 15, 2020, 163 patients including 100 males (61.3%) with the median age of 65 years (21 to 97), who underwent both RT-PCR and chest CT results were registered in the study. Low-dose chest CT protocol was applied with parameters modified from the lung cancer screening protocol. The accuracy of low-dose chest CT for COVID-19 diagnosis was evaluated, considering first RT-PCR results as reference. Results: Of 163 patients, 89 cases (54.6%) were presented with positive initial RT-PCR result. Lymphocyte percentage and lymphocyte count were significantly lower in the positive RT-PCR group (15% versus 19%, and 0.98 vs. 1.3, respectively); while, erythrocyte sedimentation rate (ESR) was significantly higher (53 vs. 22). Positive chest CT Findings were present in 133/163 cases (81.6%). The sensitivity, specificity, positive and negative predictive values (PPV and NPV) and accuracy of low-dose chest CT scan were 96.6% (95% confidence interval [CI], 90% - 99%), 36.5% (95% CI, 26% - 49%), 64.7% (95% CI, 56% - 73%), 90% (95% CI, 72% - 97%) and 69.3% (95% CI, 61% - 76%), respectively based on positive RT-PCR results. Conclusion: Low-dose chest CT scan provides both high sensitivity and negative predictive value in diagnosing COVID-19 compared to initial RT-PCR as the gold standard. It can be used as an alternate to standard-dose CT scan in areas with high prevalence of COVID-19 disease and limited availability of RT-PCR for early triage.

Ultra-low-dose chest CT protocol during the second wave of COVID-19 pandemic: a double-observer prospective study on 250 patients to evaluate its detection accuracy

“…The inter-observer agreement in this study was excellent, similar to Tabatabaei et al [18] and Dangis et al [19]. The accuracy in this study was also high but did not exceed that of Bahrami-Motlagh et al (96.6%) [20]. The CT sensitivity also in this study exceeded that in Azadbakht et al [25] (60-70%).…”

“…These estimated radiation doses are 12.5:13.3 and 18.1:20 times more than that of the low-dose and the ultra-low-dose CT protocols in this study respectively. Additionally, the DLP and absolute cancer risk of the ultra-low-dose CT in this study were lower than those provided by Tabatabaei et al [ 18 ], Dangis et al [ 19 ] and Bahrami-Motlagh et al [ 20 ]. On the other hand, the CTDIvol was higher than that provided by Shiri [ 24 ] (0.7 mGy) who used lower kV (90 kV) and lower pitch (0.8).…”

“…Comparison with Tabatabaei et al [ 18 ], Dangis et al [ 19 ], Bahrami-Motlagh et al [ 20 ] and Shiri [ 24 ] regarding the CT protocol parameters as well as the estimated irradiation doses and CT accuracy is demonstrated in Table 6 .…”

Agreement between low-dose and ultra-low-dose chest CT for the diagnosis of viral pneumonia imaging patterns during the COVID-19 pandemic

“…First, this goal was investigated using a low-dose chest CT approach (< 3 mGy) that has been recommended by some experts [ 20 , 21 ]. The evidence shows that low-dose chest CT had high sensitivity (96.6%) for triage of COVID-19 in a study by Bahrami-Motlagh et al [ 22 ] on 163 patients with suspected COVID-19 where 80 cases had positive RT-PCR results. At the next step, we intended to investigate ultra-low-dose chest CT and determine its sensitivity and specificity for triage purposes.…”

The Role of Ionizing Radiation for Diagnosis and Treatment against COVID-19: Evidence and Considerations

“…It was reported that CT examinations are mostly used to monitor the severity of disease and less for diagnostic purposes. However, in other reports, it is pointed out that there are still many countries using CT as a diagnostic tool for patients suspected of COVID-19, possibly due to limited resources [21,43]. Homayounieh's main finding was variations in the number of scan phases and CT exams per patient among healthcare facilities across the world.…”