COVID-19 CT score and oxygen saturation level on pulse oximetry: Do they correlate?

Background: Computed Tomography (CT) scan of Chest was widely used in India during COVID-19 pandemic irrespective of oxygen saturation level of the patients because of wide spread CT availability and prevalence of happy hypoxia in the COVID-19 patients. Aim and Objectives: The aim of our study was to determine the correlation between the COVID-19 CT score and oxygen saturation level on pulse oximetry in patients with Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) positive status with or without fever. Material and Methods: Those patients attending the fever clinic of our institution with suspicion of COVID-19 and were subjected to CT chest were the primary study population. Of these patients, those with positive RT -PCR status and underwent CT chest (with positive CT- severity score) and had an oxygen saturation (Sp2O ) level value on pulse oximetry were included in the study. Results: About 45.02% of the study participants had oxygen saturation below 94% and 55 % of the patients had oxygen saturation above 94%. Those with a lower saturation (<94) had higher CT mean scores in both CT25 and CT40 scoring systems. In the CT25 group, almost half of the study participants (51.1%) of those with saturation < 94% had CT scores between 6-15 (moderate category). Almost 3/4 of the study participants (72%) of those with Sp2O > 94% had CT2 scores between 6-15 (moderate category). There was a statistically significant association (p < 0.5) between oxygen saturation, gender, mortality and CT25 scores. In the CT40 group, there was a statistically significant association (p < 0.05) between CT40 scores and oxygen saturation, diabetes, hypertension and mortality. Almost 84% of those having SpO2 less than 94% had a CT score above 19 (severe category). Almost half (48%) of those with SpO2 > 94, had a CT score above 19 (severe category). Conclusions: The oxygen saturation level alone cannot be an exclusive factor in deciding whether to consider a chest CT-scan imaging, as a lot of patients with normal SpO2 had significantly higher CT-severity scores. Individuals with hypoxia have considerably higher CT severity showing substantial inverse association and the higher CT-severity score has important therapeutic and prognostic implications.