Role of Procalcitonin as an Early Marker in Diagnosis of Sepsis in Critically Ill Patient

Sepsis is the systemic response to infection by microbial organisms and is considered the leading cause of mortality in patients admitted to intensive care units (ICUs). Audits of ICU worldwide showed that 29.5% patients had sepsis on admission or during the ICU stay The signs and symptoms of sepsis are highly variable and are influenced by many factors, including the virulence and bioburden of the pathogen, the portal of entry, and the host susceptibility.

Early diagnosis of sepsis is often difficult in clinical practice, whilst it can be vital for positive patient outcomes in sepsis management. Any delay in diagnosis and treatment may lead to significant organ failure and can be associated with elevated mortality rates.

Rapid effective management of sepsis not only allows for prompt antibiotic therapy and a potential reduction in mortality, it can also minimize the unnecessary use of antibiotics.

Historically, blood cultures have been the gold standard for diagnosing sepsis, however the lenthy time to generate results is a limitation. Additionally, many patients may have already been prescribed antibiotics prior to arrival to the hospital, which may mask the presentation of sepsis in the blood culture. Despite an emphasis on isolating a specific micro organism, on average, only 34% of blood cultures are found to be positive in septic patients Therefore, while it can be useful, relying on the bacteriological diagnosis can be misleading or too late. A number of the inflammatory markers, such as leukocyte cell count, C reactive protein (CRP), and cytokines (TNF-α, IL-1β, or IL-6), have been applied in the diagnosis of inflammation and infection, but their lack of specificity has generated a continued interest to develop more specific clinical laboratory tests One promising marker has been procalcitonin (PCT), whose concentration has been found to be elevated in sepsis. Owing its specificity to bacterial infections, PCT has been proposed as a pertinent marker in the rapid diagnosis of bacterial infection, especially for use in hospital emergency departments and intensive care units.

PCT has been used as marker of sepsis with sensitivity and specificity of 83% and 62% respectively with significantly high levels in the patients having sepsis and positive blood culture results than with culture negative results PCT is a glycoprotein present in C cells of thyroid gland. It belongs to the group of related peptide (C-GRP) encoded by the CALC-1 gene and is formed from the common precursor pre-calcitonin. In healthy subjects, CALC-1 genes synthesize calcitonin, but presence of microbial infection through endotoxin or proinflammatory cytokines increases calcitonin gene expression and PCT mRNA is mostly synthesized. This lead to release of PCT from all parenchymal tissue, exclusively in response to bacterial infection only and not viral or inflammatory disease Previous studies have demonstrated that procalcitonin levels are correlated with the severity of sepsis and could potentially be used as a prognostic marker in patients with sepsis and severe sepsis In this study we evaluated the usefulness of procalcitonin as a diagnostic predictive marker of bacteremia and sepsis in critically ill patients. Serum PCT levels area useful diagnostic tool available to physicians that can help as a marker of sepsis, as well as other bacterial infections. Combination of emerging new biomarkers with PCT could be used in terms of good clinical judgement based on which antimicrobial therapy may suggested, thus reducing the prescription and duration of antibiotic treatment .