From the Guidelines
Procalcitonin should be used over CRP when suspecting bacterial infections, particularly in cases of sepsis, severe lower respiratory tract infections, or when deciding whether to initiate or discontinue antibiotic therapy, as it has been shown to have higher diagnostic accuracy and specificity for bacterial infections compared to CRP 1. When deciding between procalcitonin and CRP, it's essential to consider the clinical context and the specific advantages of each biomarker. Procalcitonin rises more rapidly than CRP, typically within 2-4 hours of infection onset, and is more specific for bacterial rather than viral infections or non-infectious inflammation 1. Some key points to consider when using procalcitonin include:
- Procalcitonin levels <0.1 ng/mL strongly suggest against bacterial infection, while levels >0.5 ng/mL suggest bacterial infection is likely 1
- Procalcitonin is useful for antibiotic stewardship, as declining levels (>80% drop from peak) indicate resolving infection and can guide antibiotic discontinuation 1
- Procalcitonin has limitations, including elevation in non-infectious conditions like trauma, surgery, and certain cancers, and may not rise appropriately in localized infections, immunocompromised patients, or with certain bacterial species 1
- While more expensive than CRP, procalcitonin's greater specificity for bacterial infections often justifies its use when bacterial etiology needs to be determined quickly or when antibiotic decisions are being made 1 In contrast, CRP is an acute-phase protein that rises in response to inflammation or infection, but its levels can be affected by neutropenia, immunodeficiency, and the use of nonsteroidal anti-inflammatory drugs 1. Overall, the choice between procalcitonin and CRP should be based on the specific clinical scenario and the need for rapid and accurate diagnosis of bacterial infections. In general, procalcitonin is preferred over CRP when suspecting bacterial infections, particularly in critical care settings where distinguishing between bacterial sepsis and non-infectious systemic inflammatory response syndrome is crucial 1.
From the Research
Procalcitonin vs CRP in Suspected Infection
- Procalcitonin (PCT) is a promising diagnostic marker for sepsis and antibiotic therapy, especially in distinguishing between bacterial and viral infections 2.
- PCT has been shown to be a helpful biomarker for early diagnosis of sepsis in critically ill patients, with a mean sensitivity of 0.77 and specificity of 0.79 3.
- Compared to C-reactive protein (CRP), PCT is more specific to bacterial infection and has demonstrated utility in risk stratification of patients with potential life-threatening bacterial infections 4.
Clinical Scenarios for PCT Use
- PCT-guided therapy can reduce antibiotic exposure without increasing mortality rates in patients with severe sepsis and septic shock 5.
- PCT testing can be cost-effective in guiding antibiotic therapy for adults with confirmed or highly suspected sepsis in intensive care settings and for suspected bacterial infection in emergency department settings 6.
- PCT algorithms can reduce antibiotic duration, hospital stay, and intensive care unit stay, with no differences in adverse clinical outcomes 6.
Key Considerations
- PCT levels can be used to monitor response to antimicrobial therapy, diagnose secondary inflammations, and diagnose renal involvement in pediatric urinary tract infection 2.
- The results of PCT tests must be interpreted carefully in the context of medical history, physical examination, and microbiological assessment 3.
- Further studies are needed to better understand the application of PCT in the diagnosis of sepsis, differentiating between microbial and non-microbial infection cases, and determining therapeutic approaches for sepsis 2, 5, 6.