Table 1. FDA/NIH biomarker categories and examples within critical care and ARDS.
| Biomarker | Definition* | Example within critical care | Example for ARDS |
|---|---|---|---|
| Susceptibility/risk | Identifies the potential to develop a disease in one who does not currently have it | Genetic polymorphism in toll-like receptor-2 in the risk of sepsis (8) | Angiopoeitin-2 predicts onset of acute lung injury in critically Ill patients (9); IL-8 is higher Bronchoalveolar Lavage fluid of those who progress to ARDS (10) |
| Diagnostic | Detects or confirms presence of disease or condition of interest; identifies individuals with subtype of disease | Cardiac ejection fraction for heart failure; creatinine and urine output in acute kidney injury | Oxygenation index; infiltrate on CXR; PaO2:FiO2 ratio |
| Monitoring | Assesses the status of a disease or condition through serial measurements; provides evidence of exposure to (or effect of) a specific product or environmental agent | PT/INR for anticoagulation; lactate in sepsis; creatinine in acute kidney injury (11) | PaO2:FiO2 ratio; oxygenation index; dead space fraction (12,13) |
| Prognostic | Identifies the likelihood of a clinical event, disease recurrence or progression in patients who have the condition of interest | PERSEVERE for risk of mortality in pediatric sepsis (14) | Biomarkers associated with mortality: Ang-2 (15); sICAM-1 (16); dead space fraction (12,13) |
| Predictive | Identifies individuals more likely to experience a favorable or unfavorable effect from exposure to a specific product or an environmental agent | Procalcitonin to guide antibiotics therapy in respiratory illness (17) | ARDS subphenotypes with different responses to fluid management strategies (18) |
| Pharmacodynamic/response | Shows a biological response has occurred in an individual who has been exposed to a medical product or an environmental agent | Lactate in sepsis after resuscitation; blood pressure in response to vasoactive medications | IL-6 decreases with corticosteroid treatment in PARDS (19) |
| Safety | Indicates the likelihood or extent of a toxicity as an adverse event after an exposure to a specific product or an environmental agent | Serum creatinine for nephrotoxic drugs; serum liver function tests for hepatotoxic drugs | Dynamic compliance measurement after recruitment maneuvers |
*, definitions obtained from the FDA/NIH BEST (Biomarkers, Endpoints and other tools) resource (7). The list of biomarkers provided in this table is not meant to be an all-inclusive list of the PARDS and critical care literature on biomarkers. Rather, it provides examples in each category to give the reader a framework in which to think about biomarker application.