From the Guidelines
To check for sepsis, the most critical laboratory tests include a complete blood count (CBC) with differential, blood cultures (at least two sets from different sites), comprehensive metabolic panel, lactate level, and procalcitonin, as these tests provide essential information for diagnosing sepsis and guiding treatment. When evaluating a patient for sepsis, it is crucial to obtain these laboratory tests promptly, as early detection and treatment significantly improve outcomes in terms of morbidity, mortality, and quality of life 1. The CBC may show elevated white blood cell count or sometimes a low count in severe sepsis, while blood cultures are essential to identify the causative organism and guide antibiotic therapy 1. Lactate levels above 2 mmol/L suggest tissue hypoperfusion and correlate with sepsis severity, and procalcitonin is particularly useful as it rises specifically with bacterial infections and can help distinguish sepsis from other inflammatory conditions 1. Additional tests often include coagulation studies (PT/INR, PTT), urinalysis and urine culture, arterial blood gases, and specific site cultures based on suspected infection source. The combination of these laboratory findings, along with clinical assessment using tools like qSOFA or SOFA scores, provides the most accurate diagnosis of sepsis, and following the guidelines from the Surviving Sepsis Campaign is recommended for the management of severe sepsis and septic shock 1. Key points to consider when checking for sepsis include:
- Obtaining at least two sets of blood cultures before antimicrobial therapy
- Measuring lactate levels to assess tissue hypoperfusion
- Using procalcitonin to help distinguish sepsis from other inflammatory conditions
- Considering additional tests such as coagulation studies, urinalysis, and arterial blood gases as needed
- Promptly obtaining these laboratory tests to improve outcomes in patients with sepsis.
From the Research
Laboratory Tests for Sepsis Diagnosis
The diagnosis of sepsis involves various laboratory tests to identify the underlying infection and assess the severity of the condition. Some of the key laboratory tests used to check for sepsis include:
- Complete Blood Count (CBC) 2, 3: A CBC is a valuable test that provides information on the patient's white blood cell count, neutrophil to lymphocyte ratio (NLR), and other parameters that can help diagnose sepsis.
- Procalcitonin (PCT) levels 4, 5: Elevated PCT levels are associated with sepsis and can be used as a biomarker to diagnose and monitor the condition.
- C-reactive protein (CRP) levels 4: CRP is a protein that increases in response to inflammation and infection, and elevated levels can indicate sepsis.
- Lactate levels 5: Elevated lactate levels can indicate tissue hypoxia and are often used to diagnose septic shock.
- Creatinine (Cre) levels 4: Cre levels can indicate kidney function and are often elevated in patients with sepsis.
- Liver function tests 4: Liver function tests, such as aspartate aminotransferase (AST) and alanine aminotransferase (ALT), can indicate liver damage and are often abnormal in patients with sepsis.
- Coagulation tests 4: Coagulation tests, such as prothrombin time (PT), can indicate coagulopathy and are often abnormal in patients with sepsis.
Biomarkers for Sepsis
Biomarkers play a crucial role in the diagnosis and management of sepsis. Some of the key biomarkers used to diagnose sepsis include:
- Neutrophil to lymphocyte ratio (NLR) 3: An elevated NLR can indicate sepsis and is often used as a biomarker to diagnose and monitor the condition.
- Procalcitonin (PCT) 4, 5: PCT is a biomarker that is often used to diagnose and monitor sepsis.
- C-reactive protein (CRP) 4: CRP is a biomarker that can indicate inflammation and infection, and elevated levels can indicate sepsis.