Using APACHE Longitudinally in ARDS to Assess Disease Severity

Introduction: The acute physiology, age, chronic Health Evaluation (APACHE) II score has been used to assess risk of mortality in admitted intensive care unit (ICU) patients since 1985. There are few examples of a longitudinal correlation over time. As the scores rises from 0 to 71, risk of mortality increases. For this study, other scores were also considered - SOFA (Sequential Organ Failure Assessment) was excluded due to a lack of variable diversity and small range of values. APACHE III and IV are more complex scores with additional variables, such that calculating daily scores manually was impracticable. APACHE II has consistent calibration compared to III and IV. We assessed whether APACHE III and IV scores had any additional benefit over APACHE II. Methods: APACHE II score was used to determine clinical severity daily of sixteen critically ill COVID-19 patients and compared to daily changes in cytokine levels. If any studies were unavailable for a given day, data was pulled from a maximum of 24 hours before or after the day of interest. Although GCS (Glasgow Coma Scale) is a large part of the score, and difficult to assess in an intubated patient, however it contributed to documenting sedation and intubation state. Results: APACHE II score assessed clinical severity daily in COVID-19 more effectively relative to SOFA. The wide score range allowed comparison of patients without overlap, as compared to SOFA which has a range of 0-24. With a larger range of 0-71, we believe that it increased the sensitivity for detection of small changes in clinical status. We analyzed APACHE II in context of absolute neutrophil count, plasma cytokine levels, as well as neutrophil functional studies. For our study, APACHE II, not SOFA, was helpful in demonstrating changes in severity of illness, which correlated with some of these assessments. For example, APACHE II showed a significant linear correlation with pro-inflammatory cytokine IL-8 in plasma (r2=0.47, p=0.0017;Fig 1). Conclusion: APACHE II was able to define the severity of illness in COVID-19 patients on a daily basis. APACHE II score allowed us to tie immunophenotyping to clinical disease severity over time and was helpful in broadening our approach to data comparison with clinical status. This was a pilot study to assess the ability of APACHE II to track severity of illness, but in the future, we plan to correlate APACHE II in a larger cohort of a variety of ARDS patients.