From the Research
Extremely high procalcitonin (PCT) levels in the Emergency Department, especially when accompanied by only moderately elevated C-reactive protein (CRP), strongly suggest bacterial sepsis requiring immediate intervention. When PCT exceeds 10 ng/mL, this typically indicates severe bacterial infection with systemic inflammatory response and possible organ dysfunction, as seen in a case report where a 76-year-old woman presented with fever, vomiting, and diarrhea, and had an extremely high level of procalcitonin, confirming the diagnosis of sepsis 1.
Clinical Significance of PCT and CRP
PCT is more specific than CRP for bacterial infections because it rises rapidly (within 2-4 hours) in response to bacterial endotoxins and inflammatory cytokines, while CRP increases more gradually and in response to various inflammatory conditions. The discrepancy between very high PCT and moderately elevated CRP often indicates early bacterial sepsis before CRP has fully increased. A study evaluating serum procalcitonin and C-reactive protein levels as diagnostic and prognostic biomarkers of severe sepsis found that procalcitonin levels are highly correlated with the severity scores regularly used in ICUs and can be used for determining the severity of the septic process 2.
Diagnostic and Prognostic Value
Procalcitonin has been shown to be a useful tool in the early diagnosis of sepsis, differentiating it from other inflammatory syndromes. A latent class approach for sepsis diagnosis supports the use of procalcitonin in the emergency room for the diagnosis of severe sepsis, with a cut-off point of 2 ng/mL suggesting a better discriminatory ability for PCT 3. Additionally, a study on burn patients found that PCT levels can be helpful in determining septic shock and bloodstream infection, with a cut-off point of 5.12 ng/mL showing reasonable discriminative power 4.
Management and Treatment
Immediate broad-spectrum antibiotics should be initiated after obtaining appropriate cultures (blood, urine, sputum, etc.), with consideration of combination therapy such as piperacillin-tazobactam 4.5g IV q6h plus vancomycin 15-20 mg/kg IV q8-12h, or meropenem 1g IV q8h with vancomycin, adjusting based on suspected source. Fluid resuscitation with crystalloids (30 mL/kg) should be started promptly, along with vasopressors if hypotension persists. Serial PCT measurements can guide antibiotic therapy duration, with decreasing levels suggesting appropriate treatment response. However, PCT elevation can occasionally occur in non-infectious conditions like trauma, surgery, or cardiogenic shock, so clinical correlation remains essential. It is also important to note that marked elevation of procalcitonin level can lead to a misdiagnosis of anaphylactic shock as septic shock, highlighting the need for careful clinical evaluation 5.
Key Points
- Extremely high PCT levels suggest bacterial sepsis requiring immediate intervention
- PCT is more specific than CRP for bacterial infections
- Procalcitonin levels can be used to determine the severity of sepsis and guide antibiotic therapy duration
- Clinical correlation is essential due to potential non-infectious causes of PCT elevation
- A cut-off point of 10 ng/mL for PCT typically indicates severe bacterial infection with systemic inflammatory response and possible organ dysfunction.