Role of Total Leukocyte Count and Platelet Count as Combined Predictors of Early Mortality in Patients with Sepsis: A Prospective Observational Study

Abstract

Background: Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Simple laboratory markers may be useful for early risk stratification where rapid access to complex prognostic tools is limited. Total leukocyte count (TLC) and platelet count are inexpensive, routinely available components of the complete blood count and may reflect inflammatory and hematologic responses to sepsis.

Objective: To evaluate the association and discriminatory performance of admission TLC and platelet count, individually and as a joint TLC-platelet classification, for 7-day mortality among adults with sepsis and leukocytosis.

Methods: This prospective observational cohort study enrolled 136 adults with Sepsis-3-defined sepsis admitted to the medical wards and medical ICU of Jinnah Postgraduate Medical Centre from March to May 2026 using consecutive sampling. For the joint classification, patients with leukocytosis were categorized as high TLC with normal platelet count or high TLC with thrombocytopenia. The primary outcome was all-cause mortality within 7 days of sepsis onset; deaths within 48 hours were recorded as an early temporal component of this endpoint. Continuous variables were compared using the independent-samples t-test or Mann-Whitney U test as appropriate, categorical variables using chi-square or Fisher's exact test, and discrimination using receiver operating characteristic (ROC) analysis with bootstrap 95% confidence intervals.

Results: Fifty-seven of 136 patients (41.9%) died within 7 days. Admission platelet count was lower in non-survivors than survivors (median 144.0 vs 186.5 ×10³/µL; p=0.044), but discrimination was weak (AUC 0.60, 95% CI 0.50-0.70). Admission TLC did not differ significantly between non-survivors and survivors (median 19.3 vs 16.5 ×10⁹/L; p=0.073) and showed similarly weak discrimination (AUC 0.59, 95% CI 0.49-0.68). Seven-day mortality was 38.2% in the high-TLC/normal-platelet group and 45.6% in the high-TLC/thrombocytopenia group (Fisher's exact p=0.49). SOFA score was higher in non-survivors (median 7 vs 5; p<0.001).

Conclusion: Among sepsis patients with leukocytosis, lower admission platelet count was associated with 7-day mortality, but neither platelet count nor TLC alone provided adequate discrimination for bedside risk stratification. The joint TLC-platelet classification also did not significantly distinguish survivors from non-survivors. These routinely available indices may complement, but should not replace, established clinical severity assessment.

Keywords: Sepsis; thrombocytopenia; leukocytosis; platelet count; total leukocyte count; early mortality; SOFA score; risk stratification