Role of IL-6 as ‘core inflammatory marker’ in assessment of severity, response to therapy and predicting outcome in COVID-19 pneumonia: A single center experience of 2400 cases in tertiary care setting in India

Abstract

Objectives: In coronavirus disease-19 (COVID-19) pneumonia, the role of various inflammatory markers including interleukin-6 (IL-6) was evolved in managing cases in indoor or critical care units worldwide. Apart from the role of IL-6 in predicting cytokine storms, the role in assessing post-COVID outcome is less studied. In the present study, we have analyzed the role in predicting ventilatory support requirement and final outcome in COVID-19 pneumonia. Material and Methods: A prospective, observational, and 12 weeks follow-up study included 2400 COVID-19 cases confirmed with reverse transcription-polymerase chain reaction. All cases were assessed with lung involvement documented and categorized on high-resolution computerized tomography (HRCT) thorax, oxygen saturation (SpO2), and IL-6 at entry point and follow-up. Covariates such as age, gender, and comorbidity; interventions such as oxygen use, bi-level positive airway pressure/non-invasive ventilation (BIPAP/NIV); and timings of ventilatory support and final outcome as with or without lung fibrosis as per computed tomography severity were recorded. Covariates were analyzed with initial and sequential IL-6 titer. Statistical analysis is done by Chi-square test. Results: The study of 2400 COVID-19 pneumonia cases, age (<50 and >50 years), gender, and comorbidity has a significant association with IL-6 titer (P < 0.00001). HRCT severity score at entry point and duration of illness has a significant correlation with IL-6 level (P < 0.00001). IL-6 titer has a significant association with SpO2 and BIPAP/NIV requirement during hospitalization (P < 0.00001). Timing of BIPAP/NIV requirement during the course of hospitalization in the intensive care unit has a significant association with IL-6 titer (P < 0.00001). Follow-up IL-6 titer during hospitalization as compared to entry point normal and abnormal IL-6 has a significant association in post-COVID lung fibrosis (P < 0.00001). Follow-up IL-6 titer during hospitalization as compared to entry point abnormal IL-6 has a significant association in predicting cytokine storms irrespective of normal or abnormal IL-6 at entry point (P < 0.0001). Conclusion: IL-6 titer has documented a very important role in triaging the COVID-19 pneumonia cases in indoor units, and guided treatments have shown improved outcomes. IL-6 titer is the “game changer” inflammatory marker not only in assessing the severity or predicting course during hospitalization but it has also helped in the utilizations of timely interventions required during hospitalizations. Sequential IL-6 titer has shown a significant role in predicting final radiological outcomes at 12 weeks.