What labs are needed to diagnose and manage sepsis?

From the Guidelines

To diagnose and manage sepsis, essential laboratory tests include a complete blood count (CBC) with differential, comprehensive metabolic panel (CMP), lactate level, blood cultures (at least two sets from different sites), urinalysis with culture, and coagulation studies (PT/INR, PTT). These tests are vital because sepsis involves complex inflammatory responses and multi-organ dysfunction, requiring comprehensive laboratory evaluation to guide timely interventions, monitor treatment effectiveness, and prevent complications 1.

Key Laboratory Tests

• Complete blood count (CBC) with differential to assess for signs of infection or inflammation
• Comprehensive metabolic panel (CMP) to evaluate organ function and electrolyte balance
• Lactate level to assess tissue perfusion and guide resuscitation efforts
• Blood cultures (at least two sets from different sites) to identify the causative organism and guide antibiotic therapy 1
• Urinalysis with culture to identify potential urinary tract infections
• Coagulation studies (PT/INR, PTT) to assess for coagulopathy

Additional Tests

• Procalcitonin to distinguish bacterial from non-bacterial causes of inflammation and guide antibiotic duration decisions 1
• C-reactive protein (CRP) to track inflammatory response
• Arterial blood gases to assess oxygenation and acid-base status
• Serial lactate measurements to monitor treatment response and guide ongoing management
• Daily CBC, electrolytes, renal and liver function tests to track organ dysfunction and guide fluid/electrolyte management

Importance of Early Identification

Early identification of the causative organism through cultures is particularly important for targeted antibiotic therapy, as it can improve outcomes and reduce morbidity and mortality 1. Prompt administration of intravenous fluids and vasopressors is also crucial in managing sepsis, with a goal of restoring a mean systemic arterial pressure of 65 to 70 mm Hg.

From the Research

Labs Needed for Sepsis Diagnosis and Management

To diagnose and manage sepsis, several laboratory tests are utilized. These include:

• Complete Blood Count (CBC) to guide clinicians in early-identifying patients at high risk of developing sepsis and to predict adverse outcomes 2
• Procalcitonin (PCT) to aid in the diagnosis of sepsis, although its efficacy is questionable, it supports antibiotic de-escalation 3
• Serial lactate measurements to monitor treatment efficacy and as part of sepsis bundles, with lactate concentrations >2mmol/L (>18mg/dL) indicating septic shock 3, 4
• Bilirubin and creatinine measurements to determine progression of organ failure, indicating a worse prognosis 3
• White blood cell count and differential as part of the initial sepsis diagnostic protocols 3
• Neutrophil to lymphocyte ratio (NLR) and the fraction of immune granulocytes, which are emerging as useful parameters in the diagnosis of septic shock 5
• Serum lactate measurement, incorporated into the latest septic shock definition, to assess circulatory, cellular, and metabolic dysfunction 6
• Sequential Organ Failure Assessment (SOFA) as an important tool for early diagnosis 6

Additional Tests and Considerations

Other tests and considerations in the diagnosis and management of sepsis include:

• Cultures to identify the source of infection 6
• Imaging studies as indicated 6
• Sepsis biomarkers such as procalcitonin and lactate levels 6
• Fluid resuscitation and antimicrobial therapy as priorities in early management 6
• Vasopressor therapy if hypotension persists despite fluid administration 6