Evaluation of the Relationship between Procalcitonin and Total Leukocyte Count, Neutrophil and Neutrophil/Lymphocyte Ratio in Patients with Systemic Inflammatory Response Syndrome and Sepsis: A Hospital-based Observational Study.

Introduction: An elevated defensive reaction of the body to a harmful stressor like infection, trauma, surgery, acute inflammation, ischemia, reperfusion, or malignancy to localize and eliminate the endogenous or exogenous source of the injury is known as systemic inflammatory response syndrome (SIRS). Sepsis is a term used for SIRS with suspected or documented sources of infection. It is characterized by the fulfillment of any two of the following conditions: white blood cell (WBC) count ≥4000/µL or >10% immature forms or bands; body temperature over 38°C or below 36°C; pulse rate above 90 beats per minute; tachypnea (respiratory rate greater than 20 breaths per minute); or partial pressure of CO₂ below 32 mm Hg. Procalcitonin (PCT) is one of the more complex and expensive lab indicators used to diagnose and prognosticate this disorder. Less expensive tests include total leukocyte count (TLC), neutrophil count, and neutrophil/lymphocyte ratio (NLR).

Objectives: To ascertain the correlation between procalcitonin and TLC, neutrophil count, and NLR in patients with SIRS without documented infection and SIRS with infection (sepsis), and to evaluate TLC, neutrophil count, and NLR ratios between SIRS without infection and sepsis.

Materials and methods: Acutely ill patients aged 18 years or older who fulfilled the criteria for SIRS were included in this study. The serum PCT value, TLC, and blood culture were done within 12 hours of admission. All other relevant investigations at the time of admission were also noted.

Results: Out of 282 patients with SIRS, 194 patients had no documented infection (group I), whereas 88 patients had a documented infection (sepsis group II). The difference in age and sex between both groups (p < 0.05) was found to be statistically significant. All four markers-PCT, TLC, neutrophils, and NLR-were significantly higher in the sepsis group.

Conclusion: PCT is the best biomarker to predict sepsis, and it correlated significantly with TLC, neutrophil count, and NLR in SIRS without infection, and with neutrophil count and NLR in sepsis in our study. Secondly, TLC and NLR are also good predictors of sepsis and can diagnose sepsis in resource-poor settings.