Diagnostic accuracy of Computed Tomography for Identifying Hospitalization in Patients with Suspected COVID-19
Background and Objectives The use of computed tomography (CT) in COVID-19 screening is controversial. The controversy is associated with ambiguous characteristics of chest CT as a diagnostic test. The reported values of CT sensitivity and especially specificity calculated using reverse transcription polymerase chain reaction as a reference standard vary widely, raising reasonable doubts about the applicability of the method. The objective of this study was to reevaluate the diagnostic and prognostic value of CT using an alternative approach. Methods This study included 973 symptomatic COVID-19 patients aged 42 17 years, 56% females. For all of them, we reviewed the disease dynamics between the initial and follow-up CT studies using a "CT0-4" visual semi-quantitative grading system to assess the severity of the disease. Sensitivity and specificity were calculated as conditional probabilities that a patient's condition would improve or deteriorate, depending on the results of the initial CT examination. For the calculation of negative (NPV) and positive (PPV) predictive values, we estimated the COVID-19 prevalence in Moscow. The data on total cases of COVID-19 from March 6, 2020, to August 24, 2020, were taken from the Rospotrebnadzor website. We used several ARIMA and EST models with different parameters to fit the data and forecast the incidence. Results The "CT0-4" grading scale demonstrated low sensitivity (28%), but high specificity (95%). The best statistical model for describing the epidemiological situation in Moscow was ARIMA(0,2,1). According to our calculations, with the predicted point prevalence of 3.9%, the values of NPV and PPV would be 97% and 18%, correspondingly. Discussion We associate the low sensitivity and PPV values of the "CT0-4" grading scale with the small sample size of the patients with severe symptoms and non-optimal methodological setup for measuring these specific characteristics. We found that the grading scale was highly specific and predictive for identifying admissions to hospitals of COVID-19 patients. Only 5% of patients assigned to home treatment were eventually hospitalized. Despite the ambiguous accuracy, chest CT proved to be an effective practical tool for patient management during the pandemic, provided that the necessary infrastructure and human resources are available.