Sepsis is a complex, life-threatening syndrome resulting from the body's dysregulated response to infection [1]. Despite advancements in modern medicine, the incidence and mortality rates of sepsis remain high globally. Early diagnosis and prompt initiation of appropriate antimicrobial therapy are critical for improving patient outcomes. The challenge in clinical practice lies in differentiating sepsis from non-infectious systemic inflammatory response syndrome (SIRS), as traditional inflammatory markers such as C-reactive protein (CRP) and total leukocyte count often lack sufficient specificity [2]. Procalcitonin (PCT), a 116-amino acid peptide precursor of the hormone calcitonin, has emerged as a superior biomarker for bacterial infections. In healthy individuals, PCT levels in the serum are extremely low (<0.05 ng/ml), as it is rapidly processed in the thyroid C-cells. However, during systemic bacterial infection, the CALC-1 gene is expressed ubiquitously in various extrathyroidal tissues, leading to a significant and rapid release of unprocessed PCT into the bloodstream [3]. Multiple studies have demonstrated that serum PCT levels correlate well with the extent and severity of bacterial infection. Unlike CRP, PCT levels rise rapidly within 2-4 hours of a bacterial trigger and peak within 6-24 hours, making it an excellent marker for early detection [4]. Furthermore, PCT levels generally do not rise significantly in viral infections or non-infectious inflammatory conditions, thus aiding differentiation [5, 6]. Due to its favourable kinetics and high specificity, PCT has been incorporated into clinical guidelines to assist in the diagnosis, risk stratification, and guiding of antibiotic therapy in patients with suspected sepsis [7]. This study aims to assess the clinical utility of serum PCT levels in a cohort of patients admitted with suspected sepsis.

Study Design and Population: This was a cross-sectional, observational study conducted in an intensive care unit (ICU) of a tertiary care hospital. A total of 50 consecutive adult patients (aged 21 years and above) with suspected sepsis, based on clinical signs and symptoms fulfilling the criteria for SIRS (Systemic Inflammatory Response Syndrome), were prospectively enrolled in the study. Patients with known medullary thyroid carcinoma or those who had undergone major trauma/surgery within the last 48 hours were excluded to avoid non-infectious causes of elevated PCT. Data Collection: Upon admission, demographic data (age and gender) were recorded. Blood samples were collected from each patient under strict aseptic precautions before the initiation of antibiotic treatment. Serum samples were analysed for quantitative PCT levels using a validated assay (e.g., fluorescence immunoassay). Procalcitonin Level Assessment: Serum PCT levels were categorised based on established clinical cut-off values: • < 0.5 ng/ml: Local bacterial infection possible; sepsis unlikely. • 0.5 – 2.0 ng/ml: SIRS; systemic infection cannot be excluded; moderate risk. • 2.0 – 10.0 ng/ml: Severe systemic inflammatory response, likely due to sepsis. • 10.0 ng/ml: Severe bacterial sepsis or septic shock. Clinical Diagnosis: The clinical diagnosis of sepsis was made independently by a treating physician using established clinical criteria (e.g., Sepsis-3 definitions or SIRS criteria with a presumed or documented source of infection), integrating clinical presentation, vital signs, and other laboratory parameters. Statistical Analysis: Data were compiled and analysed using descriptive statistics (percentages and frequencies) to summarize the distribution of age, gender, PCT levels, and diagnosis.

The study enrolled a total of 50 patients, consisting predominantly of males who accounted for 33 individuals (66%), while females made up the remaining 17 individuals (34%) of the study population (Table 1). Table 1 Gender Gender No. of Patients (%) Male 33 (66 %) Female 17 (34 %) Total 50 (100 %) Regarding patient age distribution, the cohort was primarily middle-aged to elderly. The largest single group was patients aged 41 to 60 years, representing 42% (21 patients) of the total sample. Individuals over 60 years constituted 26% (13 patients), and the youngest age bracket (21 to 40 years) comprised 32% (16 patients) (Table 2). Table 2 Age Group Age Group No. of Patients (%) 21 – 40 years 16 (32 %) 41 – 60 years 21 (42 %) > 60 years 13 (26 %) An analysis of the serum Procalcitonin (PCT) levels revealed a significant skew towards high values, indicative of severe infection. A substantial majority, 36 patients (72%), presented with levels greater than the 10.0 ng/ml threshold for severe sepsis. Only one patient each fell into the lowest two categories (< 0.5 ng/ml and 0.5–2.0 ng/ml) (Table 3). Table 3 Serum PCT Levels Serum PCT Levels No. of Patients (%) < 0.5 ng/ml 1 (2 %) 0.5 – 2.0 ng/ml 1 (2 %) 2.0 – 10.0 ng/ml 12 (24 %) > 10.0 ng/ml 36 (72 %) Finally, when correlating the PCT levels with the clinical diagnosis made by the physicians, every single patient in the study (100% or 50 patients) met the criteria for a clinical diagnosis of sepsis. This demonstrated a perfect correlation between the presentation in the ICU with suspected sepsis and the ultimate clinical diagnosis (Table 4). Table 4 Diagnosis as per PCT Levels Sepsis No. of Patients (%) Yes 50 (100 %) No 0 (0 %)

Sepsis remains a critical medical challenge, and the ability of PCT to specifically signal bacterial infection makes it a valuable adjunct to clinical judgment. The research focused on correlating a single initial PCT measurement with the established clinical diagnosis, providing demographic context regarding the age and gender distribution of the patient cohort. This observational study investigated the diagnostic efficacy of the biomarker procalcitonin (PCT) in 50 patients suspected of having sepsis within an intensive care unit (ICU) setting. The core finding was that highly elevated PCT levels were universally present in these clinically diagnosed septic patients, demonstrating a clear link between the biomarker's concentration and the presence of severe systemic infection in this specific population. This general analysis helps to validate the use of PCT as an objective tool for rapid identification of severe bacterial sepsis in high-acuity environments. The results of this study highlight the significant elevation of procalcitonin (PCT) levels in patients diagnosed with sepsis and underscore its value as a diagnostic biomarker in a high-acuity setting. Our patient cohort (n=50) showed a clear predominance of high PCT values, with 72% of patients exhibiting levels greater than 10.0 ng/ml, and a further 24% having levels between 2.0–10.0 ng/ml (Table 3). These findings strongly align with established clinical guidelines, where PCT levels > 2.0 ng/ml are highly suggestive of systemic bacterial infection or severe sepsis. The data indicate that in this specific cohort, all patients with high PCT values were concurrently diagnosed with sepsis (Table 4). This high correlation supports the findings of numerous other studies. For example, a systematic review and meta-analysis by Wacker et al. found that PCT had a pooled sensitivity of 77% and specificity of 79% for diagnosing sepsis in critically ill patients, recommending its use as a helpful marker in conjunction with clinical data [8, 9]. The extremely high levels observed in our study (>10 ng/ml) are typically associated with severe sepsis or septic shock, consistent with research suggesting that PCT levels correlate with the severity and mortality risk of the illness [9]. A study by Patil and Patil observed a slightly different distribution in their 64 septic patients, where 56.25% had PCT in the 2–10 ng/ml range and 28.13% had >10 ng/ml [10]. Our study's even higher proportion in the >10 ng/ml category may suggest a patient population with more advanced or severe stages of sepsis upon presentation. Our results, where 100% of the clinically septic patients had elevated PCT (≥0.5 ng/ml cut-off), further reinforce the biomarker's strong value. Limitations of our study include the relatively small sample size (n=50) and the lack of a control group (non-infectious SIRS patients) for direct comparison of specificity. Additionally, our study did not analyze the PCT kinetics over time or the correlation with clinical outcomes (e.g., mortality, length of antibiotic therapy), which are key areas explored in other major trials. In conclusion, our data strongly supports the use of PCT as a rapid and accurate adjunct to clinical assessment for diagnosing severe bacterial sepsis. The high levels observed validate existing literature and demonstrate its utility in identifying patients requiring immediate and intensive therapeutic intervention.

This study successfully demonstrated a strong association between elevated serum procalcitonin (PCT) levels and the clinical diagnosis of sepsis in all 50 patients within the observed cohort. The predominance of high PCT levels (> 10 ng/ml) suggests that the study population presented with severe stages of the illness. The findings reinforce the value of PCT as a reliable, objective, and timely diagnostic biomarker in the initial assessment of patients with suspected sepsis, providing crucial support for clinical decisions regarding immediate intervention.

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