Role of the QuantiFERON-Monitor in Assessing the Immune Status of Patients with Acute Respiratory Failure in Adult Intensive Care Units: A Prospective, Observational Study.

Background: The utility of the QuantiFERON-Monitor (QFM, Qiagen), a tool developed to assess general immune function, remains insufficiently explored in critically ill patients with acute respiratory failure (ARF). Therefore, we used the QFM to evaluate the immune function of patients with ARF at intensive care unit (ICU) admission and monitored QFM changes based on disease severity and clinical outcome correlations. Methods: We evaluated the immune function of 99 patients with ARF in an ICU setting. The QFM was evaluated upon ICU admission, day 7 post-ICU admission, and discharge. Their results were compared with those of five healthy controls. Results: The QFM levels at ICU admission were significantly lower in patients with ARF than in healthy controls (median IUs/mL: 5.5 vs. 465.0, respectively). The QFM levels in patients with coronavirus disease 2019 or pneumonia (9.2 and 7.9 IUs/mL, respectively) were higher than those in patients with acute respiratory distress syndrome or septic shock (4.9 and 3.6 IUs/mL, respectively). On day 7, the QFM levels increased to 8.3 IUs/mL and reached 16.7 IUs/mL at discharge. At ICU admission, patients requiring ventilator support had lower QFM levels than those requiring nasal prong or high-flow nasal cannula support. Those who died in the ICU had significantly lower QFM levels (4.0 IUs/mL) at ICU admission than those who survived (5.8 IUs/mL). Conclusions: Reduced QFM levels among patients with severe ARF reflect impaired cellular immune responses and suggest that QFM may serve as a practical tool for early risk stratification and immune monitoring in ICU settings.