Table 2.
Main host-response biomarkers used in routine practice in critically ill patients
| C-reactive protein | Procalcitonin | |
|---|---|---|
| Properties | Acute phase protein (pentraxin) | Hormokine |
| Normal values | 0.08 mg/dL (median) | < 1 ng/mL |
| Maximum peak | > 50 mg/dL (> 1000 × reference value) | > 100 ng/mL (> 10.000 × reference value) |
| Source | Liver | Virtually all cells and macrophages |
| Time to increase after insult | 4–6 h | 3–4 h |
| Time to peak concentration | 36–50 h | Around 24 h |
| Half-life | 19 h | 22–35 h |
| Possible confounders | ||
| Steroids | No effect | frequent false negatives |
| Immunosuppression | No effect | frequent false negatives |
| Neutropenia | No effect | frequent false negatives |
| Renal failure | No effect | ⬆⬆ |
| Renal replacement therapy | No effect | ⬇⬇ |
| Chronic liver failure | ⬇ (70% of the normal) | No effect |
| Acute liver failure | No CRP increase | No effect |
| Secondary infection (2nd hit) | ⬇ (70% of 1st episode) | ⬇⬇⬇ (10% of 1st episode) |
| Bacterial vs viral infections | Poor | Poor |
CRP C-reactive protein, PCT Procalcitonin