Calreticulin and GRP78 as Bioindicators for the Diagnosis of COVID-19 Pneumonia

Background: Coronavirus Disease 2019 (COVID-19) has been reported by the World Health Organization as a global health issue, leading to severe respiratory infections in humans. Recent studies have shown that endoplasmic reticulum stress can contribute to both the development and increased severity of many diseases, such as viral infections. In our study, we evaluated the diagnostic adequacy of the ER stress markers glucose-regulated protein 78 (GRP78) and calreticulin for diagnosing COVID-19 pneumonia and predicting mortality. Materials and Methods: Our study included patients who presented to the emergency department, were over 18 years of age, had at least two clinical symptoms compatible with COVID-19 pneumonia, and whose diagnosis was confirmed by polymerase chain reaction testing, and had typical findings compatible with COVID-19 pneumonia on radiological imaging. GRP78 and calreticulin levels were statistically compared between patient (n=44) and control (n=44) groups, and between patient groups (survivors and non-survivors). Results: GRP78 levels were found to be significantly greater in patients with COVID-19 pneumonia than in controls. The calreticulin levels were significantly lower. However, no significant difference was observed between the two groups in terms of survival. The sensitivity and specificity of GRP78 were 52.27% and 93.18%, respectively, when the cut-off value for GRP78 was >1.61 [area under the curve (AUC): 0.697, p<0.001]. The sensitivity and specificity were 81.82% and 72.73%, respectively, when the calreticulin cut-off was <3.96 (AUC: 0.816, p<0.001). Conclusion: Our results showed that both GRP78 and calreticulin may be good bioindicators for COVID-19 pneumonia.