Diagnostic Accuracy of Immature Platelet Fraction, Immature Reticulocyte Fraction, and Immature Granulocyte Percentage for Bacterial Sepsis: A Cross-Sectional Study

Background and objectives: Sepsis-related mortality is a global health concern. It mandates early and accurate diagnosis of sepsis. Recently, the immature platelet fraction (IPF), immature reticulocyte fraction (IRF), and immature granulocyte percentage (IGP) have been evaluated as potential biomarkers for early sepsis detection. Hence, we conducted this study to evaluate IPF, IRF, and IGP of sepsis patients. We also evaluated the diagnostic accuracy and area under the curve (AUC) of these parameters. Methods: This cross-sectional study was conducted from March 2023 to February 2025 at Kalinga Institute of Medical Sciences (KIMS), Bhubaneswar, India. We included adult patients with sepsis admitted to the KIMS medicine ICU during the study period. We recorded the following parameters assessed just after hospital admission: hemoglobin, white blood cell count (WBC), platelet count, IPF, IRF, IGP, procalcitonin, C-reactive protein (CRP), and Sequential Organ Failure Assessment (SOFA) score. All these parameters were reassessed on days 3 and 7. We then computed the sensitivity, specificity, and diagnostic accuracy of IPF, IRF, and IGP. R software (version 4.5.2, Vienna, Austria) was used for statistical analysis. Results: We analyzed 1076 sepsis patients in this study. The study population had a median age of 58.0 (46.8-64.0) years. Of them, 608 (56.5%) were male participants. On day 0, the median values of IPF, IRF, and IGP of the study population were 4.98% (4.61-5.60), 2.79% (2.48-3.19), and 3.02% (2.40-3.95), respectively. The changes in these three parameters on day 7 were statistically significant (p < 0.001). The sensitivity values for IPF, IRF, and IGP were 0.933, 0.858, and 0.671, respectively. The specificity values for IPF, IRF, and IGP were 0.959, 0.919, and 0.708, respectively. The diagnostic accuracy values for IPF, IRF, and IGP were 0.954, 0.905, and 0.700, respectively. The AUC values for IPF, IRF, and IGP were 0.998 (0.997-0.999), 0.952 (0.934-0.971), and 0.708 (0.654-0.761), respectively. Conclusion: The IPF, IRF, and IGP values at ICU admission reduced after seven days, indicating improvement in sepsis. Similarly, the SOFA scores were also reduced on day 7. The high values of IRF and IPF during admission implied increased erythropoietic and thrombopoietic actions in bone marrow. The surges in immature cell types indicated the initial stages of infection and the immunocompetent state of the patients. The high sensitivity, specificity, diagnostic accuracy, and AUC values of IPF, IRF, and IGP supported their potential as biomarkers for sepsis.