Abstract
Context: CT scan is a quick and effective method to triage patients in the Covid-19 pandemic
to prevent the heathcare facilities from getting overwhelmed. Aims: To find whether an initial HRCT chest can help triage patient by determining their
oxygen requirement, place of treatment, laboratory parameters and risk of mortality
and to compare 3 CT scoring systems (0-20, 0-25 and percentage of involved lung models)
to find if one is a better predictor of prognosis than the other. Settings and Design: This was a prospective observational study conducted at a Tertiary care hospital
in Mumbai, Patients undergoing CT scan were included by complete enumeration method.
Methods and Material: Data collected included demographics, days from swab positivity to CT scan, comorbidities,
place of treatment, laboratory parameters, oxygen requirement and mortality. We divided
the patients into mild, moderate and severe based on 3 criteria - 20 point CT score
(OS1), 25 point CT score (OS2) and opacity percentage (OP). CT scans were analysed
using CT pneumonia analysis prototype software (Siemens Healthcare version 2.5.2,
Erlangen, Germany). Statistical Analysis: ROC curve and Youden’s index were used to determine cut off points. Multinomial
logistic regression used to study the relations with oxygen requirement and place
of admission. Hosmer-Lemeshow test was done to test the goodness of fit of our models.
Results: A total of 740 patients were included in our study. All the 3 scoring systems showed
a significant positive correlation with oxygen requirement, place of admission and
death. Based on ROC analysis a score of 4 for OS1, 9 for OS2 and 12.7% for OP was
determined as the cut off for oxygen requirement. Conclusions: CT severity scoring using an automated deep learning software programme is a boon
for determining oxygen requirement and triage. As the score increases, the chances
of requirement of higher oxygen and intubation increase. All the three scoring systems
are predictive of oxygen requirement.
Keywords
Covid-19 - HRCT chest - oxygen requirement